Efficient decontamination of aqueous glyphosate using Santa Barbara Amorphous-15 (SBA-15) and graphene oxide-SBA-15 poly-amidoamine functionalized composites

There are serious concerns about the effects of aqueous glyphosate on humans especially after its re-classification as a probable carcinogen. Thus, poly-amidoamine functionalized mesoporous SBA-15 (PSBA) and graphene oxide-SBA-15 (PGOSBA) composites were synthesized and employed for aqueous glyphosate decontamination via adsorption. Glyphosate adsorption on the PSBA and PGOSBA was >= 265% enhanced than on SBA-NH2. There were fast equilibrium attainments for the composites at 30 and 60 min, respectively, and no significant differences in adsorption trend were observed as solution pH and temperature varied. The fractal pseudo-second-order kinetics model and fractal Brouers-Sotolongo adsorption isotherm model fitted the adsorption data better indicating complex glyphosate adsorption mechanisms involving electrostatic interactions, pore-filling processes, and multi-layer adsorption. The composites are reusable and stable after several cycles retaining >= 77% of their original adsorption potential after 3 consecutive cycles. The PGOSBA and PSBA composites could reduce lowconcentration glyphosate solutions to 182.9 +/- 105.7 and 235.9 +/- 4.2 mu g/L, respectively, which are below the maximum permissible limits for several countries (Canada/Argentina-280 mu g/L; the United States/China-700 mu g/L; and Australia-1000 mu g/L). These adsorbents are efficient and could be applied over wide aqueous pH, temperature, and concentration ranges, and thus would be potentially viable economically for water treatment.