Flotation Performance and Adsorption Mechanism of Cerussite with Phenylpropenyl Hydroxamic Acid Collector

Yu A., Ding Z., Yuan J., Feng Q., Wen S., Bai S.

The beneficiation of low-grade oxidized lead and zinc ore from the Lanping mine has attracted extensive interest in the mineral processing field due to the extremely rich resource reserves and the challenge in lead and zinc recovery. This study’s objective is to analyze the process mineralogy characteristics and to conduct the flotation optimization of this ore. Mineralogy parameters of the ore, such as mineral composition, mineral liberation degree, and intergrowth relationship, were investigated using an X-ray fluorescence spectrometer (XRF), an X-ray powder diffractometer (XRD), and an electronic probe microanalyzer (EPMA). The effect of the main experimental factors on the lead and zinc flotation is determined and compared. The results confirm that the low content of lead and zinc and the complex co-occurrence relationships between minerals bring a challenge to the efficient separation of the ore. Furthermore, a flow sheet consisting of “lead preferred flotation-zinc flotation” is performed, and an all-open flotation process consisted of “two-times lead rougher-one-time lead cleaner-two-times zinc rougher-one-time zinc cleaner” is finally employed for the beneficiation of this ore with the aids of mixed depressants and cationic-anionic collectors for zinc recovery. The Pb grade in the lead rougher concentrate is 2.83%, and the Pb recovery is 57.56%. The Zn grade reaches 28.64% with a recovery of 83.45%. Thus, the findings provide important technical supports for the processing of similar ores.

Shen Z., Wen S., Miao Y., Wang H., Feng Q.

Unavoidable metal ions commonly exist in the pulp during flotation. These ions can affect the floatability of minerals, and they can also result in the differences in the surface features between different minerals. In this study, how Fe3+ affected the flotation behavior of cerussite was investigated by micro-flotation tests. The corresponding adsorption characteristics of the sulfidizing agent and collector on the surfaces of cerussite were investigated by surface-analysis techniques. The results of micro-flotation tests showed that the floatability of cerussite significantly decreased when Fe3+ was added before Na2S and xanthate. The flotation recovery of cerussite decreased compared with that obtained without participation of Fe3+. Additionally, the results of xanthate and Na2S adsorption tests, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and zeta potential measurements verified that Fe3+ and its hydrophilic hydroxyl derivatives (Fe-OH compounds) resulted in reduced amounts and reactive activities of S-bearing species adsorbed on the surfaces of cerussite. This decreased the adsorption capacity of subsequently added xanthate, resulting in the difficulty in effectively recovering cerussite in the sulfidization-xanthate system.

Xue J., Qu Y., Chen Y., Zhang C., Bu X.

The sulfide flotation of cerussite by adding traditional sulfurizing reagents, such as sodium sulfide, easily loses its effectiveness when inadequate or excessive reagents are added. In this study, cerussite flotation using trithiocyanuric acid (TTCA) as a novel sulfurizing reagent was investigated. Microflotation results indicated that cerussite could be effectively collected at pH 8.0 using trace amounts of TTCA as the sulfurizing reagent. The overdose TTCA had little effect on the effective flotation of cerussite. The sulfidization mechanism of cerussite by TTCA was investigated by zeta potential measurements, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results show that TTCA was mainly adsorbed on the cerussite surface in the form of a tautomer. TTCA-Pb complexes were produced by the chemical reactions of (H2C3N3S3)- monoanions with Pb atoms, which is beneficial for the adsorption of sodium butyl xanthate on the surface. The slow-release property of TTCA was confirmed by adsorption measurements. This property prevents the addition of excess sulfurizing reagents and maintains a continuous sulfurization atmosphere to significantly improve the flotation of cerussite.

Shen L., Sun N., Xu R., Sun W., Wang L.

In this paper, the flotation separation of quartz and feldspar was studied with CaCl2 as activators and mixed sodium oleate/ dodecylamine (NaOL/DDA) collectors under alkaline condition, and the action mechanism of mixed NaOL/DDA collectors on the quartz and feldspar surfaces were systematically explored. The results of micro-flotation test showed that there were 90.98% quartz and 13.08% feldspar were floated with 0.5 mmol/L CaCl2 and 2.8 mmol/L mixed NaOL/DDA collectors with molar ratio of 8/1 at pH 10.0. And the artificial mixed minerals flotation manifested these two minerals were able to efficient separation with CaCl2 and mixed NaOL/DDA collectors at pH 10 ∼ 11. These outcomes indicated that DDA could increase recovery of quartz obviously and reduce about a half dosage of NaOL (from 0.5 mmol/L to 0.25 mmol/L) in flotation under alkaline condition; Meanwhile, mixed NaOL/DDA collectors were able to decreased the flotation separation pH from 12 to 10 on quartz and feldspar. Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results revealed that when NaOL collector was added alone, it could adsorb on activated quartz surface but hardly detected on feldspar surface at pH 10. However, they all were found on both quartz and felspar surface when mixed NaOL/DDA collectors were introduced as collectors. Quartz microcrystal balance with dissipation (QCM-D) experiment confirmed that mixed NaOL/DDA collectors showed a higher adsorption mass and more stable adsorption layer on quartz compared with NaOL was introduced as collector alone. In addition, whether CaCl2, NaOL or mixed NaOL/DDA, the adsorption mass on quartz sensor were larger than that on feldspar senor, which might cause difference of hydrophobicity on the surface of quartz and feldspar in flotation. The above experiments showed that the mixed NaOL/DDA collectors can significantly improve hydrophobic difference between quartz and feldspar after activating with CaCl2 and expand the floated pH range of quartz compared with using NaOL as collector alone, which were efficient reagents to separate quartz and feldspar in flotation.

Tang X., Chen J., Chen Y.

• Mechanism of cerussite sulfidization is studied using DFTB+ at an atomic level. • Sulfidization model of cerussite is established based on coordination chemistry. • Cerussite Pb bonds with S ligand leading to a stronger nephelauxetic effect of Pb. • Sulfidization promotes the adsorption of xanthate on hydrated cerussite surface. Cerussite (PbCO 3 ) has now attracted increasing attention due to the increasing demand of Pb metal and rapid depletion of Pb−S minerals. Sulfidization-xanthate method is effective to recover PbCO 3 . In this paper, density functional based tight binding (DFTB+) method was employed to discuss microscopic mechanism of cerussite sulfidization. Sulfidization model of a PbS film forming on PbCO 3 surface was established based on coordination chemistry of mineral flotation, changing ligand type of Pb from O ligand to S ligand. The results showed that after sulfidization surface Pb exhibited significant surface relaxation, leading to enhanced activity of Pb 4f and Pb 5f 6p orbitals. Density of state (DOS) analysis indicated that S ligand strengths nephelauxetic effect of Pb atoms, resulting in stronger covalent effect of Pb−S bonding compared with Pb−O bonding. Sulfidization turned Pb 2+ from hard acid in PbCO 3 to soft acid in PbS, making it easier to interact with butyl xanthate (soft base) but harder to interact with water (hard base). Calculation results showed that adsorption energy of water becomes less negative after sulfidization, whereas formation energy of water and xanthate co-adsorbed on sulfidized surface becomes more negative, suggesting calculation results agree with the prediction of hard and soft acids and bases (HSAB) theory.

Cao X., Huang X., Zeng J., Zhang R., Zhong H., Cao Z.

• BTHA was first introduced as a collector for the flotation of galena. • The incorporation of C-S-C group improved the molecular properties of BHA. • BTHA exhibited better collecting ability toward galena in comparison with BHA. • BTHA chemically adsorbed on the galena surface through its -C(=O)-NHOH and C-S-C groups. In this contribution, the roles of the thioether (C-S-C) group in improving the flotation performance of benzohydroxamic acid (BHA) toward galena were studied by density functional theory (DFT) calculation, adsorption experiments, zeta potential, surface energy measurements and X-ray photoelectron spectroscopy (XPS). It was found that the incorporation of C-S-C group was observed to increase the functional groups, chelating ability and hydrophobicity of BHA, thus enhance its flotation performance to galena. The adsorption mechanism analyses demonstrated that 2-(benzythio)-eacetohydroxamic acid (BTHA) molecule anchored on the galena surface mainly by the reactions of the two O atoms originated from -C(=O)-NH-OH group and lead species with the formation of a five-membered rings. Additionally, the C-S-C group in BTHA molecule could donate its electrons to lead species on galena surface, which was also helpful to the adsorption of BTHA on galena surface.

Yao X., Yu X., Wang L., Zeng Y., Mao L., Liu S., Xie H., He G., Huang Z., Zhang S.

Process diagram of flotation separation of quartz wolframite with a new hydroxamic acid collector. • Cinnamon hydroxamic acid (CIHA) was introduced as a new collector for wolframite flotation. • CIHA displayed better ability to collect wolframite than sodium oleate (NaOL). • CIHA exhibited superior selectivity for wolframite against quartz. • CIHA was adsorbed on wolframite surface by chemical adsorption. • Fe and Mn were active sites that strongly adsorbed on wolframite surface and CIHA collector. A new collector—cinnamon hydroxamic acid (CIHA)—was synthesized from methyl cinnamate using the hydroxyamine method. The results of single-mineral flotation and artificially mixed-mineral flotation indicated that CIHA had good collection performance and selectivity. Adsorption-capacity test results indicated that the CIHA collector adsorbed wolframite and quartz, and the adsorption intensity of wolframite was higher than that of quartz. The adsorption mechanism was investigated via zeta-potential analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that CIHA interacted with Mn on the wolframite surface via Pb 2+ activation to form a surface Mn–O–Pb 2+ complex, which formed a new Fe–O bond with Fe. Hydroxamic acid may have formed a five-element chelated hydroxamic group with the metal on the wolframite surface. The hydrophobicity of the wolframite surface was improved, making the wolframite more easily attach to bubbles and be more easily carried to the pulp surface.

Huang Z., Zhang S., Wang H., Liu R., Cheng C., Shuai S., Hu Y., Zeng Y., Yu X., He G., Fu W., Burov V.E., Poilov V.Z.

Tailings ponds for gangue mineral storage are widely recognized as a dangerous source of toxic minerals and heavy metal-bearing solution. Therefore, recovering valuable minerals and critical elements from tailings is an important means to protect the environment in an economic way. Wolframite tailings usually contain a considerable amount of tungsten resources, but the presence of high content of kaolinite sludge makes it very difficult to recycle wolframite. Herein, a novel sebacoyl hydroxamic acid (SHA) was synthesized and introduced as a novel wolframite collector to effectively utilize wolframite tailings, and its collection performance was compared with that of benzohydroxamic acid (BHA). Micro-flotation tests showed that SHA could still obtain 80% wolframite recovery in the presence of kaolinite slimes. Bench-scale flotation tests indicated that SHA can effectively recover wolframite concentrate with 55.64% WO 3 grade and 75.28% WO 3 recovery from wolframite tailings by the combined shaking table-flotation process. Polarized light microscope observations showed that SHA could promote the formation of hydrophobic agglomerates of wolframite particles. These results show that SHA can be used as an efficient collector for disposing of wolframite tailings, and provide an important reference for the development of efficient and comprehensive utilization of tailings. • Recovering valuable minerals was an effective way to dispose of tailings ponds. • Wolframite was recovered by combined shanking table-flotation process. • SHA showed a stronger collecting ability than traditional collector BHA. • SHA promoted the formation of hydrophobic agglomerates of wolframite particles. • SHA is hopeful to promote the development of efficient utilization of tailings.

Zhang Q., Wen S., Feng Q.

• Cu ions can interact with the sulfidized cerussite surface and form Cu-S species. • Cu-S species formed on sulfidized cerussite surfaces reduced the distribution of Pb-S species. • Addition of high concentration of CuSO 4 was harmful to the flotation of sulfidized cerussite. Cerussite, as an important metal mineral, is enriched mainly by sulfidization flotation. Ions in the pulp solution affect sulfidized cerussite flotation. In this work, the adsorption mechanism of copper ions on the sulfidized cerussite surfaces was investigated by time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, zeta potential, and ultraviolet analysis. The effect of copper ions on the flotation of sulfidized cerussite was studied by microflotation experiments. Adsorption analysis indicated that copper species adsorbed on sulfidized cerussite surfaces and change the chemical states and properties of the mineral surfaces. Copper-sulfide species were generated, which reduced the distribution of lead-sulfide species on the mineral surface. Xanthate adsorption on the sulfidized cerussite surfaces was almost unaffected at a low CuSO 4 concentration. A high CuSO 4 concentration resulted in a dramatic decrease in lead sites on the mineral surface, and excess Cu species in the pulp solution consumed xanthate, which reduced the xanthate-species adsorption on the sulfidized cerussite surfaces. Thus, the flotation recovery of sulfidized cerussite remained almost unchanged at a low CuSO 4 concentration, compared with the flotation of sulfidized cerussite without CuSO 4 treatment, whereas it was depressed at a high CuSO 4 concentration.

Zhang Q., Wen S., Nie W., Feng Q.

• Quartz could be activated when coexisting with cerussite in the pulp solution. • Flotation recovery of quartz was significantly improved after treatment with cerussite supernatant. • The difficulty of flotation separation of cerussite from quartz was greatly increased. Cerussite is an important lead oxide mineral, and quartz is the main gangue mineral. To investigate the effects of dissolved cerussite species on quartz surface properties and floatability in the sulfidization xanthate system, inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), zeta-potential, UV–visible spectroscopy, and flotation experiments were employed in this study. XPS and ToF-SIMS analysis indicated that lead species, such as Pb(OH) + , Pb(OH) 2 and PbCO 3 particulate in the cerussite supernatant can adsorb onto the quartz surface as active sites for the interaction of flotation reagents. Zeta potential and UV detection suggested that positively charged lead species interacted with the quartz surface and enhanced the adsorption of S and xanthate species. Flotation results confirmed that the flotation recovery of quartz was significantly increased after cerussite supernatant treatment, that is, quartz could be activated when coexisting with cerussite. This phenomenon greatly increased the difficulty in the flotation separation of cerussite from quartz using the sulfidization xanthate flotation method.

Luciano V.A., de Paula F.G., Pinto P.S., Prates C.D., Pereira R.C., Ardisson J.D., Rosmaninho M.G., Teixeira A.P.

• High added value products from thermal cracking of oleic acid and iron ore tailings. • Use of iron ore tailings as an iron source for the cracking of oleic acid. • Cracking reactions led to the formation of ketones, hydrogen gas and C 3 hydrocarbons. Iron ore tailings (IOT) are rich in iron oxides and silica and can be used for different applications such as allow the thermal cracking of fatty acids for the production of fuels and products with high added value. Thus, this work aimed to use of IOT as an iron source for the production of high-value products using oleic acid (OA) as carbon sources. These compounds were produced from a thermal decomposition reaction, from the mixture of OA and IOT, in a high pressure reactor (12.5 bar), using the ratio of 1:1 wt (acid:IOT), in temperatures between 250 and 450 °C (3 and 12 h). The results showed that for all reactions, the solid products obtained showed a percentage of less than 6 % of carbon material and different iron phases (Fe 2 O 3 , Fe 3 O 4 and FeOOH). For the reactions carried out at 250 and 350 °C/3h the main fraction obtained was the liquid, however the compostion was mainly the starting compound and iron oleate. For the reactions carried out at 400 and 450 °C/3h, the main fraction was gas, mainly hydrogen. For the reaction carried out at 350 °C for 12 h the mass balance showed the formation of similar amounts of liquid and gaseous products. Liquid products formed ketones as the main product, while gaseous products were identified and presented greater selectivity for C3 hydrocarbons.

Han G., Wen S., Wang H., Feng Q.

The direct sulfidization of cuprite is inefficient because cuprite is a copper-oxide mineral with a strong surface hydrophilicity. In this study, oxidant was used to modify cuprite surfaces to regulate the sulfidization of cuprite. Microflotation tests showed that the flotation recovery of pre-oxidized cuprite was nearly 25% higher than that of direct sulfidization flotation, which indicates that the cuprite surface activity was enhanced after pre-oxidation by Cu(I) species (weak affinity with sulfur ions) transformation to Cu(II) species (strong affinity with sulfur ions). Zeta potential, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry results showed that pre-oxidation improved cuprite sulfidization and promoted the formation of copper-sulfide species on the cuprite surfaces. The mineral surface stability and thus, xanthate species adsorption on the cuprite surfaces were improved. The surface-adsorption measurements and infrared spectroscopy showed that a large amount of xanthate species was adsorbed onto the sulfidized cuprite surfaces after pre-oxidation, which enhanced the cuprite hydrophobicity and improved the cuprite flotation.

Wei Q., Dong L., Qin W., Jiao F., Qi Z., Feng C., Sun D., Wang L., Xiao S.

In this study, a new flotation approach, a low-alkaline and non-desliming process, was introduced for improving lead and zinc recoveries, lowering production cost and reducing environmental pollution. Lab-scale experiments results show that the new process contributed to the flotation of the complex mixed sulfide-oxide lead and zinc ore regarding two aspects: (1) High alkaline process (pH = 12±) was replaced by low alkaline process (pH = 9±) by using collector WS (a mixture of ethyl thiocarbamate, ammonium dibutyldithiophosphate and dithiophosphate-25) and combined depressant Na 2 S/ZnSO 4 /Na 2 SO 3 for lead sulfide flotation; (2) Non-desliming process was successfully achieved by using collector MA (a mixture of ether amine, hydroxyethyl cellulose and polyacrylic acid) and combined depressant SHP/SS (sodium hexametaphosphate/sodium silicate) for zinc oxide flotation. And 43.37% Pb in the Pb concentrate was recovered, the corresponding Pb grade was 52.73%, total 84.42% Zn was recovered by the flotation of zinc sulfide minerals and zinc oxide minerals. Moreover, the two aspects of the new approach were systematically verified from lab-scale to industrial-scale application. The industrial-scale flotation tests show that Pb recovery in Pb concentrate increased by 1.86% compared with that of original system during industrial-scale tests period, and the Pb recovery increased by 4.09% compared with that of original system before industrial-scale tests period, while the Zn operating recovery in zinc oxide concentrate improved by 19.52%. Moreover, the total reagent cost of the whole new process significantly declined by 3.93 yuan per ton of ore.

Zeng Y., Yao X., Liu G., He G., Yu X., He G., Huang Z., Zhang R., Cheng C.

• Floatability of smithsonite in the presence of PHA is significantly higher than calcite. • PHA is strongly absorbed on the surface of smithsonite. • PHA exhibited excellent collecting ability for smithsonite at low dosage. • Hydrophobicity of smithsonite increased significantly in the presence of PHA. In this paper, phenylpropenyl hydroxamic acid (PHA) was synthesized and used as collector in flotation experiments. PHA was compared with sodium oleate (NaOL) and benzo hydroxamic acid (BHA) which were used in industrial production to investigate its flotation performance. Zeta potential measurement, Fourier transform infrared spectra (FTIR) measurement and X-ray photoelectron spectroscopy (XPS) measurement were carried out to revealed the interaction mechanism between smithsonite and PHA. The results of pure minerals micro-flotation experiments showed that the recovery of smithsonite reached at 90.5% while pH was 7, PHA dosage was 50 mg/L. The artificial mixed ore flotation experiments could obtain concentrate with zinc grade of 35.1% and recovery of zinc was 81.4%. Zeta potential and FTIR experiments indicated that PHA had absorbed on the smithsonite surface and changed the smithsonite surface state. XPS measurement demonstrated that PHA reacted with Zn atom and formed Zn-PHA complex which improved the hydrophobicity of the smithsonite surface, resulting in that smithsonite was easier to be attached by bubbles and carried to the pulp surface.

Xie H., Liu Y., Rao B., wu J., Gao L., Chen L., Tian X.

Here, we present a novel efficient passivation-separation method for galena and chalcopyrite that includes a novel sulfuric acid selective passivation process for galena and a special flotation process in which conventional inhibitors and collectors are not added. The surface passivation mechanism of galena was characterized by surface contact angle measurements, scanning electron and dispersive spectrometry (SEM-EDS) analysis and X-ray photoelectron spectroscopy (XPS) analysis. The contact angle measurements indicated that sulfuric acid passivation increased the surface hydrophobicity difference between galena and chalcopyrite, which led to the large difference in their floatabilities. The results of the passivation-flotation experiments for the galena-chalcopyrite mixture confirmed that the selective inhibition of galena was realized with this new process, and the floatability of galena was drastically reduced while that of chalcopyrite was slightly promoted; thus, the efficient separation of galena and chalcopyrite was achieved only with the addition of frothers. The SEM-EDS and XPS results revealed that the S element on the galena surface was gradually oxidized from S2− to SO42− during the passivation process, which generated a layer of hydrophilic lead sulfate (PbSO4), while a layer of floatable copper sulfides was formed on the surface of chalcopyrite. In this study, a new highly efficient copper-lead sulfide ore separation method was developed, and the interrelated mechanism was studied in detail.

Ren Y.S., Tynybekov B., Nurmahanova A., Ibragimov T., Kurmanbay U., Nazarbekova S., Kuatbayev A., Sartayeva A., Ilyas M., Machado da Silva Acioly T.

Sunoqrot R.M., Abidin M.H., Qian C., Jamaluddin N.

Kanwal A., ur Rehman M., Sattar R., Thebo K.H., Kazi M.

Li S., Shi Q., Li B., Yu Y.

In this study, a modified hydroxamic acid collector, tert-butylbenzylhydroxamic acid (TBHA), was used as a collector and applied to the flotation separation of cerussite and calcite. The results of single-mineral flotation experiments showed that TBHA had excellent collecting effect on cerussite, and when acidified water glass (AWG) was used as the depressant, TBHA could realize the efficient flotation separation of cerussite and calcite. The adsorption mechanism of TBHA was investigated by adsorption amount, Zeta potential, FTIR and X-ray photoelectron spectroscopy (XPS) measurements. The results of adsorption amount showed that TBHA adsorbed more on cerussite under the same conditions; the results of Zeta potential, FTIR and XPS showed that TBHA could be selectively adsorbed on the surface of cerussite in the presence of AWG. In summary, TBHA was adsorbed on the surface of cerussite by chemisorption, which enhanced the hydrophobicity of the cerussite surface. Therefore, TBHA has great potential in the flotation of cerussite.

Yang Y., Meng L., Zhou S., Xia M., Bate B.

Compared to traditional lead-remediating materials, natural-occurring paleosol is ubiquitous and could be a promising alternative due to its rich content in calcite, a substance known for its lead-removal ability via carbonate dissolution-PbCO3 precipitation process. Yet, the capability of paleosol to remediate aqueous solutions polluted with heavy metals, lead included, has rarely been assessed. To fill this gap, a series of column permeation experiments with influent Pb2+ concentrations of 2000, 200, and 20 mg/L were conducted and monitored by the spectral induced polarization technique. Meanwhile, the SEM-EDS, XRD, XPS, FTIR and MIP tests were carried out to unveil the underlying remediation mechanisms. The Pb-retention capacity of paleosol was 1.03 mmol/g. The increasing abundance of Pb in the newly-formed crystals was confirmed to be PbCO3 by XRD, SEM-EDS and XPS. Concurrently, after Pb2+ permeation, the decreasing calcite content in paleosol sample from XRD test, and the appearance of Ca2+ in the effluent confirmed that the dissolution of CaCO3 followed by the precipitation of PbCO3 was the major mechanism. The accumulated Pb (i.e., the diminished Ca) in paleosol was inversely proportional (R2 >0.82) to the normalized chargeability (mn), an SIP parameter denoting the quantity of polarizable units (primarily calcite).

Zhang H., Wang P., Shan W., Xiong Y., Xing Z., Yu H.

Rhenium is an important emerging metal material. The scarcity of reserves and the difficulty in separation and enrichment have always been important reasons restricting its industrial application. In this work, aminated SBA-15 is used as substrate for the crosslinking reaction to prepare a type of Schiff base-containing mesoporous dioxide silica material (GA-MMA-0.2N-SS) for high selectively recovering Re(VII) in aqueous solution. The results show that the using amount of APTES is small in the modification process of the adsorbent material, and the modified adsorbent still maintains the orderly mesoporous structure. The adsorption capacity of GA-MMA-0.2N-SS for Re(VII) up to 198.77 mg·g-1 under pH 1.5, and it can still reach more than 97% after 4 elution cycles. Adsorption mechanism study indicated that the complex reaction between N atoms and ReO4- is the main adsorption mechanism of Re(VII) on GA-MMA-0.2N-SS. This study provided a new adsorbent based schiff base and ordered mesoporous silica for the separation of Re(VII) from mixed solution, which also provides new ideas for the design of adsorbents in the future.

Jawhari A.H., Malik M.A., Hassan N., Fatima B.

The photocatalytic activity of magnesium oxide coupled with cadmium tungstate was observed in this study. Magnesium oxide was coupled with cadmium tungstate as using leave extract of the Brassica rapa plant. The prepared samples were characterized by various spectroscopic and microscopic techniques. As a result, it was found that the particles of the prepared sample were in the nano range. The individual crystallite sizes of magnesium oxide and cadmium tungstate in the prepared composite sample were 15 nm and 25 nm, respectively. The energy band gap for the prepared sample was found to be narrow (Eg = 2.4 eV) in comparison to the energy band gap of bare cadmium tungstate (Eg = 3.6). The zero-point charge of the prepared sample was estimated to be 6.5. The photoluminescence analysis suggested the lowering in the recombination of electron and hole heterojunction formation between magnesium oxide and cadmium tungstate in the prepared sample. The measured band edge (valence and conduction band) positions of individual semiconductors in the prepared sample suggested the formation of staggered gap (type II) heterojunction material. The heterojunction material was utilized as a photocatalyst for the photodegradation of Bismarck brown dye in water under natural sunlight irradiation. Photodegradation results suggested that the 2 g/L of sample was capable to remove ∼94% of the Bismarck brown dye from its a 20 mg/L aqueous solution within 90 minutes. The first-order chemical kinetics is reported for this study. It was found that this photocatalyst works efficiently at higher temperature and basic pH condition. The free radical scavenging and quenching experiments was also conducted. The results of the free radical scavenging experiment showed that superoxide free radicals, hydroxyl free radicals, and holes were majorly responsible for the current photodegradation process. The detailed interfacial charge transfer mechanism for the photodegradation of Bismarck brown (BBR) is also delved. Reusability and stability analysis suggested high efficiency and stability of the present photocatalyst even after five reusability cycles. The trend of the photocatalysts for Bismarck brown dye degradation under the similar condition was found to be MgO-CdWO4>MgO> CdWO4> Dark> without catalyst. The mineralization study suggested that after 280 min of sunlight irradiation only 52% mineralization could be achieved. The comparative study revealed that the efficiency of MgO-CdWO4 photocatalyst is observed better than previous reported literature.

Hosseini S., Khalaji A.D., Mokhtari A., Keyvanfard M.

Chitosan Schiff base/polyvinyl acetate (CSB/PVAc) and its Fe2O3 (CSB/PVAc@Fe2O3) nanocomposite were fabricated and characterized using different techniques, including FT-IR, XRD, SEM/EDS, BET, TGA, and DSC. They were used as suitable adsorbents for removing eosin yellow (EY), and Fluorescein (FS) dyes from the aqueous solution. The adsorption experiments were optimized by varying the essential parameters: pH solution, adsorbent dose, and contact time. Under optimum conditions (pH = 3 and 0.02 g dose of sorbents), the maximum removal efficiency was 75.65% and 95.53% for EY and 80.51% and 93.46% for FS using CSB/PVAc and CSB/PVAc@Fe2O3, respectively. Kinetic studies used pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The experimental data obeyed the intra-particle diffusion model. The adsorption data were analyzed using the Langmuir and Freundlich isotherms. According to the results, the experimental data fitted well with the Freundlich model as a heterogenous process. Finally, the removal efficiency of the new adsorbet CSB/PVAc@Fe2O3 become less active (< 7%) towards EY and FS dyes after 5 runs.

Katibi K.K., Shitu I.G., Yunos K.F., Azis R.S., Iwar R.T., Adamu S.B., Umar A.M., Adebayo K.R.

Bisphenol A (BPA) is an essential and extensively utilized chemical compound with significant environmental and public health risks. This review critically assesses the current water purification techniques for BPA removal, emphasizing the efficacy of adsorption technology. Within this context, we probe into the synthesis of magnetic biochar (MBC) using co-precipitation, hydrothermal carbonization, mechanical ball milling, and impregnation pyrolysis as widely applied techniques. Our analysis scrutinizes the strengths and drawbacks of these techniques, with pyrolytic temperature emerging as a critical variable influencing the physicochemical properties and performance of MBC. We explored various modification techniques including oxidation, acid and alkaline modifications, element doping, surface functional modification, nanomaterial loading, and biological alteration, to overcome the drawbacks of pristine MBC, which typically exhibits reduced adsorption performance due to its magnetic medium. These modifications enhance the physicochemical properties of MBC, enabling it to efficiently adsorb contaminants from water. MBC is efficient in the removal of BPA from water. Magnetite and maghemite iron oxides are commonly used in MBC production, with MBC demonstrating effective BPA removal fitting well with Freundlich and Langmuir models. Notably, the pseudo-second-order model accurately describes BPA removal kinetics. Key adsorption mechanisms include pore filling, electrostatic attraction, hydrophobic interactions, hydrogen bonding, π-π interactions, and electron transfer surface interactions. This review provides valuable insights into BPA removal from water using MBC and suggests future research directions for real-world water purification applications.

Nguyen T.T., Nguyen M.K., Kumar V., Huu Do H., Thi Kim Le A., Van Nguyen A., Gwag J.S., Nam P.C., Trung L.G.

The widespread use and subsequent release of antibiotics by humans and animals pose health and environmental risks, compelling their removal from aquatic ecosystems. MIL-101(Cr), a metal-organic framework (MOF), exhibits versatile applications in antibiotic adsorption owing to its exceptional structural characteristics. In this context, MIL-101(Cr) nanoparticles are successfully prepared via the hydrothermal method to remove pefloxacin (PEF) from aqueous solutions. The resulting MIL-101(Cr) adsorbents showcase high crystallinity (97.6%), a large surface area (3166 m2/g), broad nanopore sizes, good thermal stability, and efficient reusability. Factors including initial PEF concentration, pH, dosage of adsorbent, and temperature are thoroughly investigated. The findings reveal a good adsorption capacity (254.3 mg/g) with an optimal removal efficiency (99.7%) at 308 K in a neutral pH of 7.0 when the adsorbent dosage is 250 mg/L and the initial PEF concentration is 200 mg/L within 80 min of contact. Among the three adsorption isotherms (Langmuir, Freundlich, Temkin models), the Langmuir equation best fits the studies, indicating a maximum adsorption capacity of 253.8 mg/g at 25°C, while the experimental equilibrium adsorption capacity is 229.2 mg/g at the same temperature. Adsorption kinetics aligns with the pseudo-second-order model. Thermodynamic parameters and activation energy affirm the endothermic and spontaneous behavior of the adsorption process, attributed to both physisorption and chemisorption. This study highlights the promising potential of synthesized MOF nanocrystals as an effective adsorbent for antibiotics in wastewater treatment and environmental remediation.

Das K.P., Chauhan P., Staudinger U., Satapathy B.K.

Phosphorus to an optimum extent is an essential nutrient for all living organisms and its scarcity may cause food security, and environmental preservation issues vis-à-vis agroeconomic hurdles. Undesirably excess phosphorus intensifies the eutrophication problem in non-marine water bodies and disrupts the natural nutrient balance of the ecosystem. To overcome such dichotomy, biodegradable polymer–based adsorbents have emerged as a cost-effective and implementable approach in striking a “desired optimum-undesired excess” balance pertaining to phosphate in a sustainable manner. So far, the reports on adopting such adsorbent-approach for wastewater remediation remained largely scattered, unstructured, and poorly correlated. In this background, the contextual review comprehensively discusses the current state-of-the-art in utilizing biodegradable polymeric frameworks as an adsorbent system for phosphate removal and its efficient recovery from the aquatic ecosystem, while highlighting their characteristics-specific functional efficiency vis-à-vis easiness of synthetic and commercial viability. The overview further delves into the sources and environmental ramifications of excessive phosphorus in water bodies and associated mechanistic pathways of phosphorus removal via adsorption, precipitation, and membrane filtration enabled by biodegradable (natural and synthetic) polymeric substrates. Finally, functionality optimization, degradability tuning, and adsorption selectivity of biodegradable polymers are highlighted, while aiming to strike a balance in “removal-recovery-reuse” dynamics of phosphate. Thus, the current review not only paves the way for future exploration of biodegradable polymers in sustainable cost-effective adsorbents for phosphorus removal but also can serve as a guide for researchers dealing with this critical issue.

Khorshidi A.G., Khalaji A.D.

In this study, eco-friendly chitosan-polyvinylpyrrolidone composite (CS-PVP) was synthesized from a facile one-pot reaction at room temperature and characterized using Fourier transform Infrared (FT-IR) spectroscopy, X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and elemental mapping. Characterization results confirmed the successful synthesis of CS-PVP with rough surface morphology, good crystallinity and good thermal stability with the Tpeak of the first decomposition at 330 °C. Therefore, a batch experiment was carried out in order to remove eosin Y (EY) dye from the aqueous solution using CS-PVP. The effect of initial pH solution, sorbent dose and contact time on the removal efficiency of EY were considered. Result predicted that the adsorption capacity increased with the solution pH decreased from 5 to 3. The maximum adsorption capacity was 77.24 mg/g (98%) at pH solution of 3, adsorbent dose of 0.02 g and 180 min contact time. In addition, the adsorption process of EY was well fitted by the pseudo-first order (PFO) kinetic model and the Freundlich isotherm. The adsorption mechanism of EY using CS-PVP composite can be attributed to the different electrostatic attractions, hydrogen bonding and n–π interaction. The desorption studies of EY dye from the surface of PVP-CS showed that it is reusable. The thermodynamic parameters for adsorption of EY using CS-PVP were calculated and results confirmed that the adsorption is endothermic and spontaneous. This process is simple, low-cost and high effective in organic dye remove using the as-prepared CS-PVP composites.

Dastbaz A., Karimi-Sabet J., Amini Y., Moosavian M.A.

Pure and composite Cu-Amino-terephthalate MOF has been produced by ultrasound wave to evaluate the adsorption capacity and adsorptive separation of D2 and H2 at 77 K up to 1000 mbar. The frameworks are characterized by XRD, SEM, FTIR, ICP, BET, and EDX analysis. Separation studies were performed using idealized adsorption solution theory (IAST) and direct measurements. Isotherm studies showed the data had good agreement with the Langmuir model and the adsorption capacity of deuterium was greater than hydrogen in all samples. Linear Driving Force (LDF) model was applied to investigate the effective diffusion coefficients of deuterium and hydrogen in the frameworks. The LDF model showed hydrogen molecules diffused faster than deuterium molecules in all frameworks. In the adsorption enthalpy studies, there was a slight difference between deuterium and hydrogen adsorption energy. In this regard, Cu-BDC-NH2@rGO showed a higher adsorption enthalpy difference compared to Cu-BDC-NH2. Finally, the D2/H2 selectivity of the composite framework was greater than the pure one. Regarding this matter, the Cu-BDC-NH2@rGO MOF showed a maximum selectivity factor of about 2.2 at 77 K and 1000 mbar based on the IAST model.

Sharif M., Han T., Wang T., Shi X., Fang M., Shuming D., Meng R., Gao X.

Solvent selection and design are critical in the CO2 capture process as the choice of solvent directly impacts the cost of the process, capture efficiency, equipment size, and regeneration energy. In the present study, 1MPZ-PZ, PZ, PIP, DEEA and MEA-DEEA are analyzed in terms of interaction intensity (attractive and repulsive) and diffusivity by molecular dynamic simulation. A high intermolecular interaction intensity promotes CO2 absorption, while intra-molecular interaction intensity affects CO2 desorption during the regeneration process. Diffusivity is also an important factor for a fast CO2 uptake rate, which is desirable for efficient CO2 capture. The interpretation of diffusivity and intermolecular interaction intensity findings is conducted through mean square displacement and radial distribution function analysis, respectively. The order of interaction intensity in various amines is DEEA>MEA-DEEA>PIP>1MPZ-PZ. It shows that DEEA can increase the CO2 absorption rate as it shows the highest interaction intensity in pure and blended amine systems. The results of the intramolecular interaction intensity show that it is easier to regenerate DEEA, PIP, PZ, and 1MPZ than MEA. The temperature effect on the interaction intensity is revealed at higher temperatures, where the molecular structure becomes unstable due to higher thermal motion, which is the cause of lower interaction intensity. On the other hand, the mean square displacement analysis for the diffusivity rate shows that PZ shows the highest diffusivity rate compared to other selected solvents. The order of diffusivity rate in various pure and blended amine systems is PZ>PIP>1-MPZ-PZ>MEA-DEEA. The diffusivity of various amine solvent systems increases with temperature. As examined in this current research, assessing solvent characteristics holds significant importance in optimizing the most effective solvent system.

Obayomi K.S., Lau S.Y., Danquah M.K., Zhang J., Chiong T., Obayomi O.V., Meunier L., Rahman M.M.

Potable water availability is becoming increasingly challenging due to increasing level of global population and industrial revolution. The disproportionate use of methylene blue (MB), particularly in industrial applications, is a growing concern due to its high resistance to biodegradation and propensity to taint aquatic environments. In this study, we developed novel eco-friendly calcium oxide nanoparticles from eggshells and fishbones (CaONPs-ES and CaONPs-FB) and decorated them on graphene oxide (GO) surfaces. Both nanocomposites (CaONPs-ES@GO and CaONPs-FB@GO) were characterized using state-art-instruments and used for the removal of MB from aqueous solutions. transmission electron. Additionally, the adsorptive performance of CaONPs-ES@GO and CaONPs-FB@GO and their mechanisms of interaction with MB were investigated. BET, SEM/EDX, and XPS results revealed that the CaONPs-ES@GO and CaONPs-FB@GO were predominantly mesoporous, with surface areas of 112 m²/g and 108 m²/g, respectively. The temperature-dependent adsorption isotherms and kinetics of CaONPs-ES@GO and CaONPs-FB@GO towards MB were consistent with Redlich-Peterson and pseudo-second-order models, respectively. The Redlich-Peterson model demonstrated an adsorption similarity to the Freundlich model more than the Langmuir model, suggesting the dominance of a heterogeneous multilayer mechanism. The synthesized nanocomposites exhibited high reusability and stability for MB adsorption (>70%) even after 10 successive adsorption-desorption cycles. Thermodynamic evaluations revealed that the adsorption process was spontaneous, endothermic, and physically driven. The nanocomposites exhibited an outstanding selective adsorption behaviour towards MB from the mixture containing MB/RhB and MB/MO with separation efficiency of 99.10% and 77.34% for CaO-ES@GO, and 61.23% and 47.81% for CaO-FB@GO respectively. The particulate interaction mechanisms within the nanocomposites primarily involved π-π interaction, hydrogen bonding, pore-filling, and electrostatic attraction. The cost analysis revealed that the developed nanocomposites are more economical for treating MB in a large-scale application. Based on the statistical analysis using response surface methodology (RSM), the contributing effects of temperature and adsorbent dosage, as well as the single effect of pH, had the most significant impact on MB removal. The nanocomposites demonstrate a promising potential for sustainable MB treatment.