Adsorptive natural zeolite ceramic membrane for ammonia removal in wastewater

Abstract

Adsorption process is known as a promising way for ammonia elimination. Owing to the fact that natural zeolite (clinoptilolite) has a superior property of ion-exchange and adsorption, the removal of ammonia by natural zeolite is a strategic approach. However, the conventional approach of powder suspension adsorption might be ineffective due to some drawbacks such as the requirement of secondary treatment after the adsorption has taken place as well as the loss of adsorbent during the filtration and regeneration processes. The use of membrane technology can overcome this difficulty by combining adsorption and filtration in a single step. Therefore, this study aims to develop hybrid adsorptive natural zeolite based hollow fibre ceramic membrane (HFCM) via phase-inversion and sintering techniques. The fabrication parameters namely ceramic loading, air-gap distance, bore fluid flowrate, sintering temperature and natural zeolite clinoptilolite sieved particle size were studied. The properties of the prepared ceramic membranes were characterized in terms of morphologies, bending strengths, water permeabilities and porosities. The performance of the membrane for ammonia removal was studied using the synthetic ammonia wastewater in a crossflow system. The factors affected the adsorption performance specifically the membrane sintering temperature, natural zeolite clinoptilolite particle size, pH of the ammonia feed solution, ammonia initial feed concentration and HFCM dosage were examined in this study. The regeneration process of the used adsorptive ceramic membrane was investigated for the reusability study. Clinoptilolite has shown great potential as a good adsorptive membrane that targeting the uptake of contaminant cations in water treatment process. The results have also shown that the fabricated HFCM was successfully produced when spun at 45 wt.% ceramic loading, 5 cm of air-gap distance and 15 mL/min of bore fluid flowrate, sintered at 1050 °C and best fabricated using 36 µm sieved particle size. The produced HFCM exhibited desired morphologies with good bending strength and water permeation. The adsorptive HFCM demonstrated ammonia rejection of more than 90%. The optimization study has shown that the optimum condition of the adsorptive HFCM was found to be at pH 7.04, 75.00 mg/L and 0.35 g of feed pH, feed concentration and HFCM dosage, respectively. The optimum water permeability and ammonia removal were found to be of 281.9 L/m2?h and 94.14 %, respectively. The confirmatory test has revealed that the optimum performance was acceptable with average error of 1.64% and 1.85% for water permeability and ammonia removal, respectively.