Microfiltration of microparticulate boron adsorbent suspensions in submerged hollow fibre and capillary modules

Suspensions of a microparticulate boron adsorbent can be effectively concentrated to relatively high concentrations of about 11 mass% by microfiltration in aerated submerged modules using hydrophilic capillary and hydrophobic polypropylene hollow fibre membranes. With the increasing trans-membrane pressure difference, the permeate flux increases significantly at suspension concentrations below 7 and 4 mass% for hydrophilic and hydrophobic membrane, respectively. The permeate flux is higher for the hydrophilic membrane than for the hydrophobic one. Concentration dependence of flux for the hydrophilic membrane shows only a slight decrease of the flux with increasing concentration of the suspension, up to 7 mass%, while the flux through the hydrophobic membrane decreases much in this interval. The permeate flux at the trans-membrane pressure of 40 kPa for suspensions with 7 mass% of the adsorbent is about 72 and 14 dm3 m(2 h(1 for the hydrophilic and the hydrophobic membrane, respectively. Backwashing of the membrane with a reversed flow of permeate was tested in a module with a hydrophilic membrane and was found successful in keeping the membrane performance stable for a shorter term of operation.

Suspensions of a microparticulate boron adsorbent can be effectively concentrated by microfiltration in submerged modules using hydrophilic capillary and hydrophobic polypropylene hollow fibre membranes to a relatively high concentration of about 11 mass%. With the increasing trans-membrane pressure difference, the permeate flux increases significantly at lower suspension concentrations, below 7% in case of a hydrophilic membrane and 4% for a hydrophobic membrane. The concentration dependence of the flux for a hydrophilic membrane showed only a slight decrease of the flux, up to suspension concentration of 7 mass% while the flux through a hydrophobic membrane decreased at most in this concentration interval. Fluxes in the whole measured concentration and pressure interval were higher for hydrophilic membranes than for hydrophobic ones, which makes hydrophilic membranes more favourable for this application. For example, flux at the transmembrane pressure 40 kPa for suspensions with 7 mass% is about 20 )10(6 m s(1 (72 dm(3 h(1) for hydrophilic membranes, while for hydrophobic membranes it is only about 4 )10(6 m s(1 (14.4 dm(3 h(1). Of course, different prices of these membranes could change this preference. The specific consumption of air used in the experiments with hydrophilic membrane was about 0.42 Nm3 m(2 h(1. Backwashing of the membrane with a reversed flow of permeate, tested in module with a hydrophilic membrane, was found useful in keeping the membrane performance stable for a shorter term of operation; however, it has to be tested together with chemical cleaning of the membrane for prolonged operation in future. / /