Preparation of Sonocatalyst Fe2O3/ZnO using Sol-gel/precipitation method: characterization and removal of acid orange 7 in aqueous solution / Nur Fadzeelah A. K. and Nor Aimi Abdul Wahab

Fe2O3/ZnO composite catalyst was synthesized using a solgel/precipitation method. The synthesized samples were characterized by Xray diffraction (XRD), scanning elctron microscope (SEM) with energy dispersive X-tray spectroscopy (EDX) and Brunauer−Emmet−Teller (BET) method. The feasibility of Fe2O3/ZnO composite catalyst on the removal of Acid Orange 7 (AO7) solution was examined under an ultrasonic irradiation. The removal percentage of AO7 solution was monitored by UVvis spectrophotometer. The characterization results exhibited that the Fe2O3/ZnO composite catalyst was successfully prepared using the solgel/precipitation method. The loading of Fe2O3 particles on the surface of ZnO particles resulted in high surface area compared to ZnO catalyst. Performance wise, the highest removal percentage of AO7 solution for sonocatalytic activity (at 120 min) showed only 8.05% and 9.12% for ZnO catalyst and Fe2O3/ZnO composite catalyst, respectively. Thus, the poor removal of AO7 solution in sonocatalytic experiment using this composite catalyst indicating this catalyst is not a good potential as sonocatalyst in treatment of azo dyes. In addition, this study has revealed that Fe2O3/ZnO composite catalyst was superior to the adsorption activity in removing of AO7 from aqueous solution due to adsorption ability of Fe2O3

Effect of xylanase immobilisation conditions by combination of entrapment and covalent binding on alginate beads

The immobilisation of enzymes offer improvement in enzyme stability and characteristics as well as overcome the limitations of free enzyme systems for commercial purposes. In the current study, xylanase was immobilised using a combination technique of entrapment and covalent binding within and onto calcium alginate beads. The sodium alginate and calcium chloride (CaCl2) concentration used for the preparation of alginate beads which is the support matrix for xylanase immobilisation were fixed at 3% (w/v) and 0.3 M, respectively. The effect of immobilisation conditions (agitation rate, enzyme loading, and glutaraldehyde concentration) were studied using One-Factor-At-a-Time (OFAT) approach. The best condition for optimum immobilisation yield (83.93%) was found to be made up of the following parameter combination: agitation rate, 200 rpm; xylanase loading, 200 U; and glutaraldehyde concentration, 12% (w/w). The study shows the immobilisation conditions play a significant role towards the immobilisation yield of xylanase