Novel fabrication of the recyclable Bi7O9I3/chitosan and BiOI/chitosan heterostructure with improved photocatalytic activity for degradation of dimethyl phthalate under visible light.

Among the bismuth oxyhalides, bismuth oxide has the shortest band gap and high absorption power in the visible light region. Dimethyl phthalate (DMP) has been identified as endocrine-disrupting plasticizer and emerging pollutant, which was selected as the target pollutant to evaluate the efficacy of the studied catalytic process. In this work, Bi7O9I3/chitosan and BiOI/chitosan were efficaciously synthesized by the hydrothermal process method. Characterizing prepared photocatalysts was done by employing transmission electron microscopy, X-ray diffraction, scanning electron microscopy energy-dispersive spectroscopy, and diffuse reflectance spectroscopy. For this study, the test design was performed using the Box-Behnken Design (BBD) method in which the variables of pH, Bi7O9I3/chitosan dose, and dimethyl phthalate concentration were examined for the catalytic removal of dimethyl phthalate in the presence of visible light. Our detected results disclosed that the order of efficiency in DMP removal was as follows: Bi7O9I3/chitosan > BiOI/chitosan > Bi7O9I3 > BiOI. Also, the maximum pseudo-first-order kinetic coefficient for Bi7O9I3/chitosan was 0.021 (min)-1. When the synthesized catalysts were exposed to visible light irradiation, the predominant active species were O2- and h+ for degradation of DMP. The study on the reuse of Bi7O9I3/chitosan showed that this catalyst could be reused 5 times without significant reduction in efficiency, which indicates the cost-effectiveness and environmental friendliness of using this catalyst.

Scallop shell coated Fe2O3 nanocomposite as an eco-friendly adsorbent for tetracycline removal.

ABSTRACTThe present study focused on the usability of scallop shell coated Fe2O3 nanoparticles as an eco-friendly new absorbent in the treatment of tetracycline (TC). The process performance in terms of TC removal was investigated at different operating conditions, i.e. at solution pH of 3-11, Fe2O3-scallop dosage of 0.4-2.4 g L-1, initial TC content of 20-120 mg L-1 and temperature of 25-55°C. Solution pH of 7 yielded the highest TC removal efficiency (99%). At this pH value, almost complete TC removal was achieved at a Fe2O3-scallop shell nanocomposite dose of 1.6 g L-1 and 25°C. The responsible TC removal mechanism is suggested as the non-electrical π-π dispersion interaction between the bulk π system on the absorbent surface and TC molecules bearing both benzene rings and double bonds at this solution pH. TC removal efficiency appreciably enhanced up to the Fe2O3-scallop dosage of 1.6 g L-1 being an optimum. Adsorption rate was found to be fast at lower initial TC concentrations than 40 mg L-1. The effect of temperature on TC removal efficiency was insignificant. Adsorption followed the pseudo-second-order kinetic model. Experimental data perfectly fitted by the Langmuir equation. The maximum adsorption capacity was calculated as 49.26 mg g-1. Thermodynamic analysis demonstrated that adsorption process was spontaneous process and endothermic. The results obtained from the present study proved the excellent performance of scallop shell coated Fe2O3 nanoparticles as an eco-friendly adsorbent in TC treatment.