Removal of a potentially hazardous chemical, tetrakis (hydroxymethyl) phosphonium chloride from water using biochar as a medium of adsorption

The research investigates the efficiency of biochar to eliminate an emerging contaminant, flame retarding chemical, a.k.a. Tetrakis (Hydroxymethyl) Phosphonium Chloride (THPC) from water. The THPC, which is a water-soluble, organophosphorus salt, is mainly used by textile industries as a flame retardant and crease resistant for cotton and cellulose fabrics. Our research explores the possible removal process of THPC from water while using biochar as a mode of adsorption. Commercial biochar was used to investigate the adsorption efficiency of THPC. Spectroscopic and surface characterization data were provided for the commercial biochar. Study showed the presence of several organic functional groups on biochar which have potential to contribute to an efficient adsorption process. Batch adsorption studies were conducted varying several parameters like biochar dosages, contact time of the substrate to biochar, agitation time, and temperature during the experiment. It was found that benign experimental conditions such as lower biochar dosage, lower temperature and lower agitation time maximized the adsorption capacity. Furthermore, biochar was chemically treated with various activation agents and the removal efficiency was compared between activated and non-activated biochar. It was found that chemical activation on biochar indeed improved the THPC removal efficiency. Results also indicates that the adsorption mechanism of THPC on to biochar surface followed both Langmuir and Freundlich isotherms. Finally, it was observed that the adsorption process was fitted best with pseudo-second-order kinetic model which might indicate a possible chemisorption mechanism for the adsorption of THPC on biochar surface. (C) 2018 Elsevier B.V. All rights reserved.