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Developing an organic template-free zeolite coated on a low-cost ceramic support is essential to reduce the overall cost of the membrane for heavy metal separation. In this study, a low-cost and highly durable kaolin-supported zeolite-coated composite membrane was fabricated and tested for removal of cerium metal ions from its aqueous solution. Different strategies were followed to fabricate the composite membrane through the organic template-free hydrothermal synthesis method, such as coating the ceramic tubes solely on the interior surface, exterior surface, and both sides. The results obtained from X-ray diffraction, field emission scanning electron microscopy, and field emission transmission electron microscopy indicated that the hydrothermal synthesis route produced pure, ultrafine, and uniform particles of chabazite zeolite with a cation exchange capacity of 3.96 meq/g. The effect of coating on the membrane surface(s) was investigated by measuring the weight increment, porosity, pore size, and pure water permeability; the results revealed that the ceramic tube coated on both sides has the highest amount of zeolite loading, that is, 1.82 ± 0.18 g, along with a porosity of 30.50 ± 0.50%, a water permeability of 1.74 L/m2h bar, and an average pore diameter of 36 nm. The average pore diameter of the composite membrane (both-side-coated tubes) obtained from BET analysis (34 nm) was in good agreement with the pore size (36 nm) estimated through the pure water permeability test. Furthermore, the performance of the composite membrane coated on both sides was evaluated toward removing cerium ions from aqueous solutions. The effect of applied pressure, pH, and concentration of the feed solution was investigated. During the cross-flow filtration tests, the permeate flux decline was not observed for all the applied pressures. More than 99.9% removal of cerium was achieved under the different conditions of feed concentration and pH. This study establishes the application of the prepared composite membrane for cerium removal from aqueous solutions.

Abstract: The presence of notable quantities of oil in water is one of the prime causes of water pollution worldwide. The increased water pollution is creating nuisance to human and animal lives. To put an end to this threat, the treatment of oily wastewater is attracting everyone’s attention. The high efficacy of membrane filtration in separation operations makes researchers consider this technology for use in oily wastewater treatment. Hence, keeping this perspective in mind, tubular configuration membranes were fabricated using kaolin (30 wt %), quartz (30 wt %), calcium carbonate (28 wt %), boric acid (4 wt %) and feldspar (8 wt %). Membrane fabricated with this composition is found to possess a porosity value of 59.27 ± 1.002% and mechanical strength of 14.708 ± 2.603 MPa along with an average pore size of 0.092 μm. The surface of the membrane is smooth and free of any defects as observed under field emission scanning electron microscope. The membrane, due to its satisfactory physical and mechanical properties, is further used for the treatment of oily wastewater with three various concentrations and complete rejection of oil is achieved for all the concentrations. The successful separation of oil from the oily wastewater signifies size exclusion to be the dominant phenomenon for the rejection performance of the membrane. The droplet size distribution of the oil-in-water emulsion using laser particle size analyzer also reveals the same, with an average droplet size of oil lying between 2.884–3.802 μm for all three concentrations. The size of the droplets is far bigger than the average pore diameter of the membrane, which ultimately helps the membrane in retaining the oil content of wastewater. Therefore, looking at the outstanding oil removal efficiency of the membrane, it can be concluded that the membrane can be used industrially for the treatment of oily wastewater.