Abstract

Zinc deplating waste liquid is considered hazardous due to the presence of heavy metal Zn(II) and hydrochloric acid, along with Fe(II). This study aims to develop a new adsorbent for efficient separation of zinc (II) from deplating waste liquid in a real factory. The novel adsorbent, PSCL-CQDs-NH2, was prepared by grafting home-made amino-rich carbon quantum dots (CQDs-NH2) onto a chloromethyl polystyrene resin matrix. It has been observed that amino groups can be protonated under strongly acidic conditions, enabling them to adsorb negatively charged Zn(II)-Cl complexes while repelling positively charged Fe(II)-Cl complexes. The grafted nano-size CQDs-NH2 can offer more adsorption positions to improve the adsorption properties. The results shown that PSCL-CQDs-NH2 presented higher Zn(II) adsorption capacity and better performance in separating Zn(II) from Fe(II) compared to the conventional anion exchange resin (717). At 298 K, PSCL-CQDs-NH2 showed a maximum Zn(II) adsorption capacity of 201.77 mg/g, and a selective Zn(II)/Fe(II) separation factor of 3033.72, which were 54.7% and 45.4 times higher than those of 717 resin. In the fixed bed adsorption process, PSCL-CQDs-NH2 exhibited 61.5% higher adsorption performance than 717 resin when treating actual zinc deplating waste liquid. Moreover, the water consumption during regeneration of PSCL-CQDs-NH2 is reduced by 10.3% compared to the 717 resin. These findings indicate that PSCL-CQDs-NH2 is an effective material for the treatment of industrial zinc deplating waste liquid.

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