Application of alkaline sludge based LDHs in Cd and Cu polluted wastewater remediation: Process and mechanism

The alkaline sludge produced by the neutralization treatment of acid mine drainage (AMD) is not only large and difficult to treat, but also prone to secondary pollution. The cost of conventional sludge treatment technology is high, so there is an urgent need to develop new methods. The process of neutralizing AMD is similar to the co-precipitation reaction of LDHs, so the cost of recovering LDHs from AMD is lower, but the application performance of LDHs is limited by the stacking of laminates. In this paper, the structure of LDHs was optimized by adding biochar (BC) during the neutralization process of AMD. After adding 40 % BC, the crystal planes of alkaline sludge based LDHs (AS-LDHs) became more parallel, and the adsorption properties of Cd and Cu were increased by 2.7 and 1.95 times, with the maximum adsorption amounts of 901.5 and 231.3 mg/g, respectively. The relevant removal mechanism was investigated in depth at the electronic scale by experiments combined with DFT calculations. Since AS-LDHs have the advantages of good acid stability, low zero-point charge and strong adsorption and regeneration capacity, this method has a broad application prospect.