Eco-friendly, high-effective, and biocompatible sorbent based on specially designed hydroxyapatite nanoparticles for wastewater treatment from non-ionic surfactants

A new approach to the development of sorbents based on surface-modified hydroxyapatite (HAp) nanoparticles (NPs) for extraction of nonionic surfactants is proposed and tested. The essence of the approach is the building HAp NPs through a non-classical oriented attachment (OA) mechanism from smaller NPs under hydrothermal treatment. Based on characterization data and quantum-chemical calculations, a possible mechanism for final NPs formation is suggested. An additive of ammonium nitrate was used as a source of ammonium ions to specifically regulate the process of OA impacting the size of final NPs, the increase of additive amount resulted in the final NPs size decrease. An original procedure for NPs surface modification by fatty acids in order to create required for sorption of nonionic surfactants combination of hydrophobic and hydrophilic areas was developed. Obtained NPs were used as sorbents for extraction of nonionic surfactant Triton X-100 from aqueous solutions, including solutions based on water taken from city water channel, showing extraction efficiency up to 100 %. The extraction efficiency is determined not only by the fatty acid used for surface modification, but also by the location of modifier on NP surface.