MOF composites derived BiFeO3@Bi5O7I n-n heterojunction for enhanced photocatalytic performance

BiFeO3 is a photocatalyst with excellent performance. However, its applications are limited due to its wide bandgap. In this paper, MIL-101(Fe)@BiOI composite material is synthesized by hydrothermal method and then calcined at high temperature to obtain BiFeO3@Bi5O7I composite material with high adsorption capacity. Among them, An n-n heterojunction is formed, which improves the efficiency of charge transfer, and the recombination of photo-generated electrons and holes prevents the improvement of photocatalytic efficiency and stability. The result of photocatalytic degradation of tetracycline under visible light irradiation showed, BiFeO3@Bi5O7I (1:2) has the best photodegradation effect, with a removal rate of 86.4%, which proves its potential as a photocatalytic degradation material.

Adsorption of fluoride from industrial wastewater using polymer adsorbents: a review

Fluoride pollution in ground and surface water originates from naturally occurring reactions and industrial activities such as the disposal of industrial wastewater. Amongst different fluoride removal technologies including chemical precipitation, membrane filtration, ion exchange processes, and electrodialysis, adsorption is an attractive method for fluoride removal from wastewater due to its low operational cost, simplicity, and good sustainability. Various adsorbents are used for fluoride removal including, metal oxides and hydroxide, carbonaceous adsorbents, zeolite, polysaccharides, and polyresin adsorbents. This review studies the application of modified polysaccharides and polyresin adsorbents for the removal of fluoride from wastewater. The relationship between the adsorption conditions and the resulting adsorption capacity is thoroughly discussed. Based on the reported studies, modified polysaccharides and polyresins adsorbents can effectively remove fluoride from wastewater achieving high adsorption capacity, the highest being 92.39 mg/g for aluminum impregnated amberlite at pH 3. Furthermore, aluminum impregnated adsorbents reported a higher fluoride adsorption capacity than other modification methods where the three adsorbents with the highest fluoride adsorption capacity are: aluminum impregnated amberlite 92.39 mg/g at pH 3> zirconium immobilized crossed linked chitosan 48.26 mg/g at pH 6 > chitosan/aluminum hydroxide beads 17.68 mg/g at pH 4. In addition, polymeric adsorbents are also highly sustainable as they can be regenerated multiple times to be reused. Therefore, the high adsorption capacity and good regeneration potential allow polymeric adsorbents to serve as promising and sustainable adsorbents to remove fluoride from industrial wastewater.

Super-Adsorbent Hydrogels for Removal of Methylene Blue from Aqueous Solution: Dye Adsorption Isotherms, Kinetics, and Thermodynamic Properties

Removal of dyes through adsorption from wastewater has gained substantial interest in recent years, especially in development of hydrogel based adsorbents, owing to their easy use and economical nature. The aim of the present study was to design a super-adsorbent hydrogel based on sodium styrenesulfonate (NaSS) monomer for removal of dyes like methylene blue (MB). NaSS displays both an aromatic ring and strongly ionic group in its monomer structure that can enhance adsorption capacity. Poly(sodium styrenesulfonate-co-dimethylacrylamide) hydrogels were prepared by solution free radical polymerization using gelatin methacryloyl (GelMA) as crosslinker, creating a highly porous, three-dimensionally crosslinked polymer network contributing to higher swelling ratios of up to 27,500%. These super-adsorbent hydrogels exhibited high adsorption capacity of 1270 mg/g for MB adsorption with above 98% removal efficiency. This is the first report for such a high adsorption capacity for dye absorbance for NaSS-based hydrogels. Additionally, the adsorption kinetics using a pseudo-first-order and the Freundlich adsorption isotherm models for multilayer, heterogeneous adsorption processes has been reported. The adsorbents’ reusability was confirmed through 4 repeated cycles of desorption-adsorption. The results discussed herein illustrate that NaSS based chemistries can be used as an efficient option for removal of organic dyes from contaminated wastewater.