Synthesis of sodalite octahydrate zeolite-clay composite membrane and its use in separation of SDS

A simple two-step process for synthesis of sodalite octahydrate zeolite-clay composite, charged ultrafiltration membrane is described wherein the active layer is obtained by partial plugging of the pore-mouth of macroporous clay support with in situ grown zeolite particles. Dip-coating of zeolite synthesis solution at pH 12 is found to give higher deposition of zeolite on the clay support. Increase in amount of zeolite in the active layer obtained by repeated deposition of zeolite particles on clay-support is quantified using membrane potential measurements and it is found that four cycles of zeolite deposition gives optimum results. The membrane is characterized using SEM for surface morphology, XRD for zeolite characterization, water flux and separation of surfactant (SDS) above cmc concentration. SDS separation results show observed-rejection in the range of 10–45%. The observed-rejection is found to decrease with increase in the applied pressure difference and increase with increase in the surfactant concentration. The permeate flux is found to reduce significantly to about 0.2–0.46 times the pure water flux. The trend is similar to that reported in literature for separation of surfactant micelle by ultrafiltration membrane of pore size much larger than the size of surfactant micelle.