This research studied influencing factors for removing copper in synthetic wastewater using Mg-based replacement reaction. Magnesium (Mg) metal was used as a reducing agent, was simply oxidized to Mg²⁺ in the synthetic wastewater while Cu²⁺ was reduced to Cu metal. Effects of molar ratio of Mg to Cu²⁺, initial pH and contact time were examined in batch experiments. Initial and residual concentrations of Cu²⁺ were determined by Atomic Absorption Spectrophotometer. The experimental results showed that the optimum molar ratio of Mg to Cu²⁺,  initial pH and contact time were 2.5, 2 and 45 minutes, respectively. The concentration of copper (II) ions in synthetic wastewater was reduced from 4,651.7 mg L^-1 to 842.99 mg L^-1. The removal efficiency of copper was 81.88 %. An equation of reaction rate constant was y = -0.023x + 8.002 which assumes to be first order reaction.

Keywords: heavy metals, copper, magnesium, redox reactions, replacement reaction