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.

No abstract

No abstract

A highly-efficient graphitic carbon nitride (g-C3N4) photocatalyst for visible light photodegradation of rhodamine B (RhB) and methyl orange (MO) simulating dyeing wastewater was synthesized by the thermal polycondensation of melamine. The photocatalysts were characterized by TG-DTG-DSC, XRD, EA, XPS, FT-IR, SEM, TEM, BET, PL and UV-vis DRS. The results showed that the photocatalytic performance of g-C3N4 at a higher calcination temperature was significantly enhanced, and its photocatalytic activities for the photodegradation of RhB and MO were remarkably improved by 64.91% and 41.83%, respectively, which was mainly attributed to the satisfactory crystallinity, stable graphene-like structure, large surface area, and excellent optical properties. It was found that •O2− radicals and •OH radicals were the main active species for the photodegradation process by the free radicals trapping experiments and ESR analysis. The photodegradation mechanism of g-C3N4 was proposed predicated using the characterization results.

No abstract