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

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 481.85 mg/g, which is much higher than that of other reported adsorbents in the presence 16% NaCl. 2  mol/L NaOH, 2  mol/L H2SO4 and 2  mol/L Fe2(SO4)3 could all be used to achieve over 97% regeneration of R-Fe3+.

Adsorption performance of salicylic acid on a novel resin with distinctive double pore structure.

Two approaches were used to synthesize two resins with different pore structures. In one way, the CH2Cl groups in macroporous chloromethylated polystyrene resin were transformed to methylene bridges, and achieved a hypercrosslinked resin with plentiful micropores (denoted GQ-06). In the other way, 50% of the CH2Cl groups in chloromethylated polystyrene resin was used to produce micropores, while the residual 50% of the CH2Cl groups was reacted with 2-aminopyridine, and prepared another resin with double pore structure of hypercrosslinked resin and macroporous resin (denoted GQ-11). The adsorption of salicylic acid (SA) on GQ-11 was investigated using GQ-06 as the reference adsorbent. The effect of pH on the adsorption of SA on GQ-06 was consistent with the dissociation curve of SA. The maximum adsorption capacity of SA on GQ-11 was observed at the solution pH of 2.64. The greater adsorption rate of SA on GQ-11 than that of GQ-06 was attributed to its double pore structure. The multifunctional adsorption mechanism of anion exchange and hydrophobic interaction resulted in the larger equilibrium capacity of SA on GQ-11 than that of GQ-06. GQ-06 and GQ-11 could be regenerated by absolute alcohol and 80% of alcohol -0.5mol/L of sodium hydroxide aqueous solution, respectively.

Effects of the steric hindrance of micropores in the hyper-cross-linked polymeric adsorbent on the adsorption of p-nitroaniline in aqueous solution.

A hyper-cross-linked polymeric adsorbent with "--CH2--phenol--CH2--" as the cross-linked bridge (denoted GQ-05), and another hyper-cross-linked polymeric adsorbent with "--CH2--p-cresol--CH2--" as the cross-linked bridge (denoted GQ-03) were synthesized to reveal the effect of the steric hindrance of micropores in the hyper-cross-linked polymeric adsorbent on adsorption capacity and adsorption rate of p-nitroaniline (PNA) from aqueous solution. The results of adsorption kinetics indicated the order of the adsorption rate GQ-05>GQ-03. The pseudo-first-order rate equation could describe the entire adsorption process of PNA onto GQ-05 while the equation characterized the adsorption process of GQ-03 in two stages. The order of the adsorption capacity GQ-05>GQ-03 was demonstrated by thermodynamic analysis and dynamic adsorption. The steric hindrance of micropores in the hyper-cross-linked polymeric adsorbent was a crucial factor for the order of the adsorption capacity and adsorption rate.