title: Integration of ceramic membrane and compressed air-assisted solvent extraction (CASX) for metal recovery.
abstract: In our previous publications, compressed air-assisted solvent extraction process (CASX) was developed and proved to be kinetically efficient process for metal removal. In the current study, CASX with a ceramic MF membrane integrated for separation of spent solvent was employed to remove and recover metal from wastewater. MF was operated either in crossflow mode or dead-end with intermittent flushing mode. Under crossflow mode, three distinct stages of flux vs. TMP (trans-membrane pressure) relationship were observed. In the first stage, flux increases with increasing TMP which is followed by the stage of stable flux with increasing TMP. After reaching a threshold TMP which is dependent of crossflow velocity, flux increases again with increasing TMP. At the last stage, solvent was pushed through membrane pores as indicated by increasing permeate COD. In dead-end with intermittent flushing mode, an intermittent flushing flow (2 min after a 10-min or a 30-min dead-end filtration) was incorporated to reduce membrane fouling by flush out MSAB accumulated on membrane surface. Effects of solvent concentration and composition were also investigated. Solvent concentrations ranging from 0.1 to 1% (w/w) have no adverse effect in terms of membrane fouling. However, solvent composition, i.e. D(2)EHPA/kerosene ratio, shows impact on membrane fouling. The type of metal extractants employed in CASX has significant impact on both membrane fouling and the quality of filtrate due to the differences in their viscosity and water solubility. Separation of MSAB was the limiting process controlling metal removal efficiency, and the removal efficiency of Cd(II) and Cr(VI) followed the same trend as that for COD.
authors.affiliation: Department of Water Resources and Environmental Engineering, TamKang University, 151 Ying-Chuan Road, Tamsui 25137, Taipei, Chinese Taiwan. chiwang@mail.tku.edu.tw
authors.forename: Chi-Wang
authors.initials: CW
authors.lastname: Li
authors.forename: Chun-Hao
authors.initials: CH
authors.lastname: Chiu
authors.forename: Yu-Cheng
authors.initials: YC
authors.lastname: Lee
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Chang
authors.forename: Yu-Hsun
authors.initials: YH
authors.lastname: Lee
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Chen
mesh_terms: D057919:Biological Oxygen Demand Analysis; D002516:Ceramics; D058868:Compressed Air; D004655:Emulsions; D004867:Equipment Design; D008567:Membranes, Artificial; D019216:Metals, Heavy / Q000302:isolation & purification*; D008962:Models, Theoretical; D012997:Solvents / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D004655:Emulsions; D008567:Membranes, Artificial; D019216:Metals, Heavy; D012997:Solvents; D014874:Water Pollutants, Chemical