Surface Modification of Hydrophobic Resin with Tricaprylmethylammonium Chloride for the Removal of Trace Hexavalent Chromium

Chromium(VI) is one of the most toxic contaminants in the environment, even at low concentration. The conventional chemical precipitation process for Cr(VI) wastewater treatment becomes less effective at low Cr(VI) concentration. By a two-step solvent–nonsolvent method, tricaprylmethylammonium chloride (Aliquat 336) can be immobilized onto the surface of porous Amberlite XAD resin with good stability, giving Aliquat 336-modified resins (AMRs). Furthermore, the exposure of the cationic ammonium functional group facilitates the adsorption and stripping efficiency of Cr(VI). The amount of immobilized tricaprylmethylammonium chloride was 2.0 mmol/g of resin. A kinetic study showed that the adsorption of Cr(VI) was under film-diffusion control followed by intraparticle-diffusion control. The Cr(VI) adsorption capacity was as high as 1.37 mmol/g. More than 99% of the adsorbed Cr(VI) could be stripped during regeneration. For stability and reusability, the AMRs maintaine da high level of Cr(VI) adsorption even after four cycles of adsorption/stripping. The experimental results for actual wastewater demonstrated that the AMRs can be used effectively for the treatment of trace Cr(VI)-containing wastewater.