EXPERIMENTAL AND THEORETICAL STUDY OF SODIUM CHLORIDE AND CALCIUM CHLORIDE TRANSPORT THROUGH CELLULOSE ACETATE MEMBRANES USING A REVERSE OSMOSIS BATCH CELL.

摘要

Unsteady-state nature of Reverse Osmosis batch cell made it difficult to collect accurate data. Unsteady-state behavior has been investigated theoretically and empirically. Quasi-steady state equation is used to determine the steady state permeate concentration in R-O batch cell and gives accurate estimation of time required to reach steady state. Extensive steady state R-O data were collected for NaCl, CaCl(,2), NaCl + CaCl(,2) using three CA Membranes. Pusch(1977) showed that 1/R = A + B 1/J('2) where R is rejection coefficient and J(,v) is total volume flux through membrane. Most of our R-O data show linear relationship between 1/R and 1/J(,v) does occur. In general, data follows Kadem-Katchalsky model which predicts intercept A as greater or equal to unity and the linear relationship between 1/R vs. 1/J(,v). For NaCl an increase in feed concentration caused increase in slope B: for CaCl(,2), increase in feed concentration causes decrease in in slope B. A few investigations showed the predicted linear relationship between 1/R and 1/J(,v) does occur experimentally, but slope, B, varies with feed concentration in some cases and not in others. This conflict is resolved by applying Glueckauf's(1976) electrodynamic theory for partition coefficient which arrised in the quantity B. Using Glueckauf's theory can estimate the pore radius of a membrane in addition. Experimental results indicate variation in the slope B with respect to feed concentration is minimal when using high feed concentrations or membranes with large pores. Feasibility of hardness removal by R-O was also considered. Experimental results indicate the rejection coefficient of CaCl(,2) is much greater than that of NaCl for the same normal concentration. It is possible to achieve more than 97% rejection of CaCl(,2) using R-O. Multisolute (NaCl + CaCl(,2)) experiments were performed and its data obtained follow the multi-solute diffusion model. Increase in rejection coefficient for CaCl(,2) and decrease in the rejection coefficient for NaCl, as compared to rejection coefficients obtained from single solute experiments, were observed.(, )