Photocatalytic degradation of 2,4-dicholorophenoxyacetic acid by TiO2 modified catalyst: kinetics and operating cost analysis.

Effective pesticide remediation technology demands amendments in the advanced oxidation process for its continuous treatment and catalyst recovery. The evidence of 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide in water bodies, poses a major environmental threat to both humans and aquatic organisms. In the present study, a recirculation type photocatalytic reactor was developed to treat 2,4-dichlorophenoxyacetic acid using chitosan-TiO2 beads prepared via impregnation method under UV light. At optimized conditions, chitosan-TiO2 beads showed a maximum photocatalytic degradation of 86% than commercial TiO2 (65%) and followed pseudo first-order reaction. The 2,4-D degradation follows pseudo first-order kinetics under UV irradiation with a rate constant of 0.12 h-1, and the intermediates were identified using LCMS analysis. The total operational cost of the chitosan-TiO2 catalyst was found to be profitable (Rs. 1323 for 2 L) than that of TiO2 (Rs. 1679) at optimized conditions. The beads were reusable up to 4 consecutive cycles without loss in efficiency. This study briefs photocatalytic removal of 2,4-dichlorophenoxyacetic acid in a recirculation-type reactor for its reliability, low cost, efficiency, reusability, and commercialization.

Immobilized TiO2/chitosan beads for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid.

Advancement in photocatalysis is focused on large-scale commercialization where the immobilization techniques gain attention with an aim to recover and reuse the catalyst for the redemption of pollutants. TiO2 will act as a potential catalyst and chitosan, a natural biopolymer is used to immobilize TiO2. 2,4-Dicholorophenoxyacetic acid, a common broadleaf pesticide found in surface and groundwater is taken as a model pollutant. Thus, the objective is to study TiO2/chitosan beads for the degradation of 2,4-dicholorophenoxyacetic acid. TiO2/chitosan beads were prepared by the phase inversion method and studied for their morphological and physiological features. The beads were observed to be spherical in shape and X-ray diffraction analysis shows the incorporation of chitosan and TiO2. The photocatalytic degradation of 2,4-dicholorophenoxyacetic acid showed 92 % degradation for TiO2/chitosan beads in UV light. The results were also compared with bare TiO2, and extended to the continuous photocatalytic mode of degradation. The kinetics and stability of the TiO2/chitosan beads were monitored for their feasibility.

Nitrate decontamination through functionalized chitosan in brackish water.

N, N, N-Triethyl ammonium functionalized cross-linked chitosan beads (TEACCB) was prepared by alkylation of glutaraldehyde cross-linked chitosan beads to remove nitrate from brackish water. Physico-chemical characteristics of TEACCB were analyzed using FTIR, SEM, EDAX, TGA, DTA, BET surface area, swelling ratio and pHzpc. The maximum nitrate removal capacity of TEACCB was 2.26meq/g and is higher than other reported chitosan based adsorbents. Nitrate removal ratio in the presence and absence of common anions like chloride and sulphate demonstrated the selectively of TEACCB towards nitrate. The kinetic data of nitrate removal fitted well with the pseudo-second-order kinetic model. The thermodynamic parameters indicated that nitrate removal could be spontaneous and exothermic in nature. TEACCB was reused with 100% efficiency after regenerating with 0.05N HCl. Column study was carried out to remove nitrate from brackish water. These results are very significant to develop TEACCB based nitrate removal technology with great efficiency.