Removal of heavy metal ions from multi-component aqueous solutions by eco-friendly and low-cost composite sorbents with anisotropic pores

Copper, nickel, zinc, chromium, and iron ions are the prevailing contaminants in the aqueous effluents resulting from the photo-etching industry. In this context, we investigate here the metal ion sorption performance of an ion-imprinted cryogel (IIC), consisting of low-cost materials coming from renewable resources, towards multicomponent metal ion solutions. The IIC sorbent, which is based on a chitosan matrix embedding a natural zeolite, was synthesized using a straightforward strategy by coupling copper-imprinting and unidirectional ice-templating methods. As consequence, the 1D-orientation and the interconnectivity of flow-channels sustain the fast metal ion diffusion within the IIC anisotropic structure. The removal efficiency of IIC sorbent reached 50% after 30 min, and the sorption equilibrium was attained within 150 min. For assessing the successful formation of imprinted cavities with well-defined sizes controlled by the radius of copper ions used as template, selectivity studies were performed on binary, ternary, and five-component synthetic mixtures. The efficiency of IIC as sorbent was further evaluated on real-life aqueous effluents discharged from photo-etching processes; thus, an IIC dosage of 6 g L-1 was found to remove 98.89% of Cu2+, 94.56% of Fe3+, 91.67% of Ni2+, 92.24% of Zn2+, and 82.76% of Cr+ ions from this type of industrial wastewaters.