Cyanide removal from industrial praziquantel wastewater using integrated coagulation–gas-filled membrane absorption

Gas-filled membrane absorption has been used to remove cyanide from different cyanide containing wastewaters. In this study, cyanide removal from an industrial praziquantel wastewater has been investigated. The wastewater contained a high cyanide concentration and turbidity due to the presence of lipophilic colloids. During cyanide removal, the membrane was severely fouled by these lipophilic colloids. In order to overcome membrane fouling, an integrated coagulation–gas-filled membrane absorption process is proposed. Coagulation is used to remove the lipophilic colloids before cyanide removal in the subsequent gas-filled membrane absorption step. By using this integrated process, the turbidity of the wastewater was decreased from 100–800 NTU to 10–40 NTU. Further the cyanide concentration was reduced from 1000–3500 mg/L to below 0.5 mg/L. More than 98% of the cyanide could be recovered and reused.