High adsorption capability of chlorpyrifos and Congo red in aqueous samples by a functionalized dextrin/graphene oxide composite

Design and suggestion of the efficient methods for fast removal of the contaminants from water resources have always been one of the most essential topics in the field of environmental sciences. In this regard, we designed a natural-based adsorbent system for efficient removal of chlorpyrifos (CPF) pesticide and Congo red (CR) dye from the aqueous samples. In this way, dextrin (DEX), graphene oxide (GO), and 3-aminopropyl triethoxysilane (APTES) have been used to construct a stable composition in nanoscale that includes several advantages as follows: low cost in preparation, biocompatibility, high efficiency due to huge surface area and high porosity, and etc. From chemical aspect, simultaneous utilization of both acidic and basic functional groups on DEX–3-aminopropyl silane (APS)/GO surfaces resulted in a great upshot in the adsorption process. This is clearly shown that the presence of the amine groups significantly affects the adsorption process, over a short contact time. The main driving forces in the adsorption process by the designed adsorbent system are л–л stacking, electrostatic and hydrogen bond interactions. In summary, all effective factors on the adsorption process of the CR and CPF, i.e., solution pH (4–9), adsorbent dosage (5–25 mg), contact time (5–35), and initial concentration of organic pollutants (50–300), have been experimentally investigated in this account. As well, three isotherm models (Langmuir, Freundlich, and Temkin) and two kinetic models (pseudo-first order and pseudo-second order) have been studied for the DEX–APS/GO adsorbent system. It has been revealed that the Freundlich isotherm model with pseudo-first-order kinetic is followed by DEX–APS/GO adsorbent system in CPF/CR removal process. Overall, the maximum adsorption capacity (Qm) of the prepared adsorbent system for CPF and CR was found 769.231 and 909.091 mg/g using 5 mg of DEX–APS/GO, with an initial concentration of 300 mg/L of pollutants at pH 4 and 6, within 30 and 15 min, and agitated at 25 °C. The prepared adsorbent was reused for ten successive adsorption–desorption runs without a considerable reduction in the adsorption efficiency. Various characterization techniques confirmed the successful synthesis of DEX–APS/GO adsorbent. The result of characterization revealed that the prepared adsorbent system exhibited high thermal stability with about 85% char yield by heating up to ca. 600 °C, whereas its component, i.e., DEX and GO, showed low thermal resistance. Furthermore, the FESEM and XRD results showed that ECH-functionalized GO was well intercalated into the polymeric matrix of DEX–APS. Based on the obtained results, the designed product is suggested to be fabricated in high scale and then exploited in the industrial applications.