Abstract
A mordenite framework inverted (MFI) type zeolite membrane was produced on inexpensive tubular ceramic substrate through hydrothermal synthesis and applied for the removal of chromium from synthetic wastewater. The fabricated ceramic substrate and membrane was characterized by diverse standard techniques such as X-ray diffraction, field emission scanning electron microscope, porosity, water permeability and pore size measurements. The porosity of the ceramic substrate (53%) was reduced by the deposition of MFI (51%) zeolite layer. The pore size and water permeability of the membrane was evaluated as 0.272 μm and 4.43 × 10–7 m3/m2s.kPa, respectively, which are lower than that of the substrate pore size (0.309 μm) and water permeability (5.93 × 10–7 m3/m2s.kPa) values. To identify the effectiveness of the prepared membrane, the applied pressure of the filtration process and initial chromium concentration and cross flow rate were varied to study their influence on the permeate flux and percentage of removal. The maximum removal of chromium achieved was 78% under an applied pressure of 345 kPa and an initial feed concentration of 1,000 ppm. Finally, the efficiency of the membrane for chromium removal was assessed with other membranes reported in the literature.
Highlights
In recent years, environmental concerns have been increasing, on the subject of heavy metals’ existence in water
All the raw materials used for fabrication of the ceramic substrate were examined using X-ray diffraction (XRD) and the obtained patterns match well with the Standard Joint Committee on Powder Diffraction Standards (JCPDS) files
The XRD peaks of the kaolin are in good agreement with the reflections of standard JCPDS card number 14–164 and the other additional reflections match with the JCPDS card number 10–446
Summary
Environmental concerns have been increasing, on the subject of heavy metals’ existence in water Heavy metals, such as chromium, lead, cadmium, mercury, nickel, copper and zinc, are, unlike organic contaminants, non-biodegradable and lead to accumulation in the human body, which causes health hazards due to their toxicity. A variety of techniques have been established to treat chromium, including chemical precipitation (Gheju & Balcu ), liquid–liquid extraction (Sacmaci & Kartal ), chemical/electrochemical reduction (Dhaz et al ), ion-exchange (Rengaraj et al ), solvent extraction (Luo et al ), adsorption (Selvi et al ), coagulation/flocculation (Amuda et al ), dialysis (Koseoglu et al ) and reverse osmosis (Rad et al ) Most of these methods have disadvantages, such as the need for pretreatment, usage of additional costly chemicals, longer operation period, etc.
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