Removal of Cu²⁺ from aqueous solution using proton exchange membrane by Donnan dialysis process

In the context of increasing heavy metal pollution (e.g., Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺) in Liao River Basin of China in recent years due to metallurgical refinery, this study investigated the removal of Cu²⁺ from aqueous solution by Donnan dialysis process. Na⁺ was selected as the counterion, while GEFC-107 proton exchange membrane (GEFC Co., China) was used as the ion exchange membrane. Transport of Cu²⁺ from feed phase to receiver phase was enhanced by increasing \({{{\text{Na}}_{\text{R}}^{ + } } \mathord{\left/ {\vphantom {{{\text{Na}}_{\text{R}}^{ + } } {{\text{Cu}}_{\text{F}}^{{ 2 { + }}} }}} \right. \kern-0pt} {{\text{Cu}}_{\text{F}}^{{ 2 { + }}} }}\) ratio (subscripts R and F denote as receiver and feed phases, respectively). For the initial Cu²⁺ concentration of 200 mg L⁻¹ and \({{{\text{Na}}_{\text{R}}^{ + } } \mathord{\left/ {\vphantom {{{\text{Na}}_{\text{R}}^{ + } } {{\text{Cu}}_{\text{F}}^{{ 2 { + }}} }}} \right. \kern-0pt} {{\text{Cu}}_{\text{F}}^{{ 2 { + }}} }}\) ratio of 20:1, a removal efficiency of 95.31 % was achieved for 190 min dialysis. The adsorption percentage by the proton exchange membrane increased from 12.12 to 85.15 % when the initial Cu²⁺ concentration decreased from 200 to 20 mg L⁻¹. The kinetics data for Cu²⁺ removal was best interpreted by the first-order model. The removal efficiency decreased from 89.09 to 72.43 % when the proton exchange membrane was reutilized three times without membrane washing using acid. Higher initial pH of receiver phase or lower initial pH of feed phase facilitated the Cu²⁺ transport from feed to receiver phase. The feasibility of Donnan dialysis collaborated with precipitation to remove Cu²⁺ was found to be not suitable for Cu²⁺ removal with high concentration, i.e., initial concentration 200 mg L⁻¹, since only a removal efficiency of Cu²⁺ of 54.08 % was achieved.