Modification On PVDF Membrane And Applications Of Membrane Separation In Hydrometallurgy Of Copper

Abstract:Membrane separation process is a novel technology applied in separation, concentration and purification with high efficiency. Modifications on membrane preparation material and applications of membrane separation are always the focus of membrane technology research. In this paper, modifications on PVDF membrane to improve its poor mechanical strength and hydrophilicity prepared by immersion precipitation were investigated as well as membrane separations applied to hydrometallurgy of copper process based on its current situations with low-copper and high-iron in bioleaching solution. Hence, the conclusions were made as follows:(1) The effects of the three main elements on performance of membrane prepared by immersion precipitation in PVDF/PVP/DMAc/water system were investigated in orthogonal experiment. The results showed that the optimums of membrane performance including membrane pure water flux, rejection and tensile strength were achieved under the conditions of20wt%PVDF,3wt%PVP and0.15mm membrane thickness. It provided the valuable references for the next modification on membrane about mechanical strength and hydrophilicity.(2) Tensile strength modifications on PVDF membrane were investigated by adding HDPE. Results showed that the optimal tensile strength of membrane which contained HDPE2wt%, PVDF20wt%and3wt%PVP was achieved, ie2.48MPa; Hydrophilicity modification on PVDF membrane were also investigated by adding PMMA. Results showed that the membrane reached the optimal performance when PVDF:PMMA was6:4and polymer concentration was20wt%in membrane prepared solution.(3) The bioleaching solution of Dexing copper mine were treated by the process of deironing by goethite process, pretreatment by ultrafiltration and concentration by nanofiltration. The results showed that: the optimum of deironing was achieved when the temperature to be30℃and terminal pH value ranging from3.0-3.2, deironing rate was above80%and copper loss rate was below2%; after ultrafiltration pretreatment to deironing solution under the conditions of feed pressure to be0.60MPa, temperature to be30℃, flow rate to be17L·min-1and concentration times to be10, a large proportion of Fe(OH)3colloid and particulates were rejected, and most of the Cu2+passed into the penetrate; and then, after nanofiltration under the conditions of feed pressure to be1.50MPa, temperature to be30℃, flow rate to be18L·min-1and concentration times to be5, Cu2+concentration in solution was increased to0.526g·L-1,2.38times of that in original bioleaching solution. The extraction performances before and after process treatment were compared, and it indicated that both of the extraction rates of original bioleaching solution and concentrated solution were above99.5%under the conditions of the initial pH of feed, phase ratio to be1:1, extractant concentration to be2%and extraction time to be180s, but Cu2+concentration in organic phase, the latter was2.37times the former. This suggested that the process applied in bioleaching solution above was technologically feasible and had great significances on productivity and cost reduction.(4) Pilot scale test of the process of deironing by goethite process, pretreatment by ultrafiltration and concentration by nanofiltration to bioleaching solution of heap leaching plant in Dexing copper mine was carried out stably. Under the conditions of ambient temperature to be30℃and terminal pH value ranging from3.0-3.2by either natural phase separation or fast phase separation by flocculant addition, the good performances of deironing were reached, copper loss rate was lower than3%and the deironing rate was67%-80%. After10times concentration by ultrafiltration and4times concentration by nanofiltration, the copper concentration was concentrated to be2.8-2.9times the one before process. Besides, the performance of membrane recovered well by washing after contaminated by experiments.