Preparation of a novel non-burning polyaluminum chloride residue(PACR) compound filler and its phosphate removal mechanisms.

As an inevitable industrial by-product, polyaluminum chloride residue (PACR) will cause serious harm to the environment if directly buried and dumped. The aim of this paper was searched a new economical, environmental, and practical way of utilization for PACR. In this paper, a novel non-burning PACR compound filler was made from mainly PACR. The prepared compound filler has excellent physical properties and phosphate adsorption efficiency of up to 99.9%. Static adsorption experiments showed that the adsorption process of phosphorus by the compound filler conformed to the pseudo-second-order kinetic model and intra-particle diffusion model. Langmuir and Freundlich isotherm models described the phosphorus adsorption process well, and the maximum phosphate adsorption capacity arrived at 42.55 mg/g. The phosphate adsorption by the compound filler is a spontaneous endothermic process. The main mechanisms are ligand exchange and Lewis acid-base interactions; calcium and aluminum play important roles in the adsorption of phosphorus by the compound filler. Dynamic column experiments showed that as much as 90% of the phosphorus removal by compound filler, and the phosphorus concentration decreased from 1 to ~0.1mg/L. The results provide a new waste resource utilization method for PACR and show the good application potential of prepared compound filler in constructed wetlands.