Sustainable utilization metal ions of acid leaching clay wastewater to fabricate adsorbents for high- efficient removing Congo red and Methyl violet

Recycling waste into efficient adsorbents to remove pollutants again provides a compa-tible solution for the sustainable development of water resources. Here, Mg2+, Al3+, and Fe3+ metal ions from oxalic acid leaching mixed-dimensional palygorskite clay waste-water were successfully converted into mixed metal oxides (MMOs) through a simple precipitation-calcination process. MMOs prepared under different precipitation pH con-ditions or different washing schemes were used to remove the anionic dye Congo red (CR) and cationic dye Methyl violet (MV). The relatively pure Mg-Al-Fe MMO obtained at pH 13 with thorough washing had ultrahigh adsorption capacity for CR, up to 1369 mg/g. In the presence of sodium oxalate byproducts without washing, the prepared MMOs containing Fe3O4, sodium carbonate, and carbon byproducts had higher removal capacities for ca-tionic dye MV, with a maximum of 1098 mg/g. Moreover, the series of MMOs exhibited strong removal capability for CR + MV mixed dyes and satisfactory cycle stability. This work provided a new perspective on the sustainable utilization of mineral resources and water resources.& COPY; 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.