D151 resin preloaded with Fe3+ as a salt resistant adsorbent for glyphosate from water in the presence 16% NaCl.

Abstract

D151 resin preloaded with Fe3+ [denoted as R-Fe3+] was to investigate R-Fe3+ as an adsorbent for glyphosate from water in the presence high concentration of salt. The adsorption mechanism revealed the coordination of Fe3+ inside R-Fe3+ with O atoms of P-O and N atoms in glyphosate molecule. The adsorption capacity of glyphosate by R-Fe3+ was much larger than that of D151 resin preloaded with Ni2+, Cu2+, Na+ and H+. Even in glyphosate solutions containing 16% NaCl, R-Fe3+ showed the constant adsorption capacity of glyphosate. The result provided the first evidence of R-Fe3+ as a salt resistant adsorbent for glyphosate. The adsorption capacity of glyphosate was the maximum at pH 3.35. The adsorption thermodynamics showed that the adsorption of glyphosate by R-Fe3+ was the ligand exchange of glyphosate and water. The maximum coordination ratio of glyphosate to Fe3+ inside R-Fe3+ was 1:1. The maximum adsorption capacity of glyphosate by R-Fe3+ was up to 481.85mg/g, which is much higher than that of other reported adsorbents in the presence 16% NaCl. 2mol/L NaOH, 2mol/L H2SO4 and 2mol/L Fe2(SO4)3 could all be used to achieve over 97% regeneration of R-Fe3+.