Resource Utilization of Waste Salt from Coal Chemical Industry by Bipolar Membrane Electrodialysis with Heat Pretreatment

Abstract

The aim of this study is to explore the feasibility of applying bipolar membrane electrodialysis (BMED) into the coal chemical waste salt treatment.  The real waste salt containing 0.54% of the organics proportion from coal chemical industry was tested in the BMED with different pretreatments.  Without any pretreatment on the waste salt, high concentration of organics in 250 g/L waste salt solution caused the fouling of anion exchange membrane (AEM), resulting in increased AEM ohmic resistance from 21 ± 2 Ω to 32 ± 3 Ω in the BMED at the current density of 50 mA/cm2 within 180 min.  Heat pretreatment at 850 oC within 30 min completely removed the organics in the waste salt with forming the insoluble calcium and magnesium compounds, resulting in efficient control of AEM fouling.  In the 850 oC heat pretreatment with BMED process, the energy consumption was 2.50 ± 0.08 kWh/kg·NaOH and 3.10 ± 0.20 kWh/kg·HCl with 58.2 ± 1.0 g/L base and 42.6 ± 1.3 g/L acid production within 180 min, respectively.  Our results should be useful for the resource utilization of the waste salt from coal chemical industry.

Keywords: Coal chemical waste salt, Bipolar membrane electrodialysis, Heat pretreatment, membrane fouling, Resource utilization