Preparation of a novel adsorbent with amino-rich carbon quantum dots for efficiently separating Zn(II) from Fe(II) in zinc deplating waste liquid

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-NH 2 , was prepared by grafting home-made amino-rich carbon quantum dots (CQDs-NH 2 ) 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-NH 2 can offer more adsorption positions to improve the adsorption properties. The results shown that PSCL-CQDs-NH 2 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-NH 2 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-NH 2 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-NH 2 is reduced by 10.3% compared to the 717 resin. These findings indicate that PSCL-CQDs-NH 2 is an effective material for the treatment of industrial zinc deplating waste liquid.