Copper removal from stormwater using powdered activated carbon water treatment residual coated steel slag

Copper (Cu) is a common stormwater contaminant originating from traffic-related sources, posing risks to aquatic ecosystems due to its toxicity and persistence. Effective and sustainable treatment solutions are needed to prevent its accumulation in water bodies. The objective of this study was to develop a new adsorbent by physically binding powdered activated carbon water treatment residuals (PAC-WTR) and steel slag for Cu removal from stormwater. The generated adsorbent (PAC-SS) was characterized using SEM-EDS, which confirmed the uniform coating of PAC-WTR on steel slag, while FTIR analysis before and after adsorption identified key functional groups involved in Cu binding. Batch adsorption experiments showed rapid Cu removal within the first 3 h, with equilibrium reached in 12-24 h, and higher PAC-SS dosages enhancing removal efficiency. The presence of deicing chemicals (NaCl, CaCl₂ and MgCl₂) in the range of 0.001-0.1 M had a limited effect on Cu removal by PAC-SS. Coexisting humic acid, Pb²⁺, and Zn²⁺ reduced Cu removal efficiency by up to 29.5 %, 25.1 %, and 7.9 %, respectively. Desorption experiments demonstrated that adsorbed Cu remained stable in the presence of deicing chemicals, while recovery using 0.1M and 1.0M HCl achieved 70.1 % and 76.8 % efficiency, respectively. PAC-SS maintained Cu removal above 73 % during five adsorption-desorption cycles using 0.1 M HCl. Finally, a column study using real stormwater demonstrated that PAC-SS effectively removed multiple contaminants, with Cu removal remaining stable (82-87 %) over 432 empty bed volumes. These results suggest that PAC-SS is an effective adsorbent for Cu removal and recovery from stormwater while promoting the beneficial reuse of industrial byproducts for environmental protection.