Preparation of Quaternary Ammonium Salt-Modified Chitosan Microspheres and Their Application in Dyeing Wastewater Treatment.

An efficient adsorbent (a quaternary ammonium salt-modified chitosan microsphere, CTA-CSM) was synthesized via an emulsion cross-linking reaction between 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA) and chitosan (CS). The adsorption efficiency of the CTA-CSM as an adsorbent was studied using methyl orange dye to evaluate its suitability for wastewater purification. The characterization results showed that the CTA groups were successfully grafted onto the CS microspheres, and the as-prepared CTA-CSM samples exhibited a smooth surface and good dispersibility. The modification of CTA on CTA-CSM significantly improved its ability to remove methyl orange dye. The adsorption process of methyl orange by CTA-CSM was well described by the Langmuir isotherm model and followed the pseudo-second-order kinetic model. Under the optimal conditions, the maximum removal rate (98.9%) and adsorption capacity (131.9 mg/g) of CTA-CSM was higher than those of other previous reports; its removal rate for methyl orange was still up to 87.4% after five recycles. Hence, CTA-CSM is a very promising material for practical dyeing wastewater purification.