Background: Laccase enzyme is capable of oxidizing many resistant and non-biodegradable environmental pollutants, so it has been studied frequently in recent years and is widely used in biodegradation of contaminants. Despite its abundant applicability, due to its short life span, nonrecovery, thermal instability and instability in organic environments, its widespread use is very limited. The present study aimed to increase the stability of laccase by immobilizing it on silica coated iron oxide nanoparticles. Materials and Methods: Fe3O4 nanoparticles were synthesized based on the co-precipitation method and after coating with silica, their surface was modified by amine groups. The enzyme was then immobilized by covalent binding using glutaraldehyde. Specifications of synthesized nanoparticles and immobilized enzyme were investigated using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Energy-dispersive X-ray spectroscopy (EDX). Results: Results of successful laccase immobilization on nanoparticles showed that laccase immobilization significantly increased storage and thermal stability, maintaining activity in a wider range of temperature and pH than free laccase. Conclusion: The immobilization of laccase on silica-coated iron oxide nanoparticles can reduce the barriers and challenges of various enzymes by increasing its efficiency and stability.

Background and purpose: Catechol is a ring form organic compound with high toxicity that is used in petrochemical, pharmaceutical and manufacturing of pesticide. It has adverse effects on human and environmental health if discharged into the environment. The purpose of this study was removal of catechol using catalytic ozonation using core-shell magnetic nanoparticles of iron oxide doped with silica and titanium dioxide from aqueous solution.Materials and methods: We conducted a basic-applied study in which magnetic nanoparticle Fe3O4@SiO2@TiO2 was synthesized using sol-gel method. To determine the characteristics of nanoparticle, XRD, SEM and EDX tests were used. Then effect of different parameters on removal efficiency were investigated. These included solution pH (2-10), reaction time (0-60 min), dose of catalyst (0.2-3 gr/L), initial concentration of catechol (50-1000 mg/L), recycled test (7 times), and determining the mineralization and scavenger effect. The residual concentration of catechol was measured using high-performance liquid chromatography at 275 nm.Results: The optimal pH for the catalytic ozonation process was 8. The maximum efficiency of the process in optimal conditions (catechol concentration 1000 mg/l, pH=8, catalyst dosage 3 gr/L and dose of ozone 0.38 gr/hr) was 100% after 60 minutes of contact time. Kinetics of degradation of catechol followed first degree model. After reaction time the amount of mineralization was 91.5%. Reusability of catalyst was done 7 times and its efficiency decreased by about 4%. Scavenger (1 gr/l tert-butanol) decreased removal of catechol by 4.16%.Conclusion: The catalytic ozonation process using Fe3O4@SiO2@TiO2 nanoparticles in an alkaline pH was found to be capable of eliminating high concentrations of catechol effectively.

The quality of silica used in glass industry effects the quality of product in a great deal. Presence of iron oxide causes different colors in glass and therefore is considered as an impurity. In this article ways for iron oxide reduction has been evaluated for the silica originated from Ghermez Abad mine using flotation. Flotation tests were designed either as direct or reverse and different collectors were applied either individually or collectively. Results showed that a dual collector system and pulp pH around 2-2.5 presents the optimum conditions. Increasing the conditioning time did not affect the iron oxide reduction process. For over 6 minutes it even showed an adverse effect as increasing the conditioning time from 6 to 9 minutes increased the iron oxide grade from 0.022% to 0.0238%. The optimum solid percentage was also found to be at 30%. Frother type and additional collector concentration did not lower iron oxide grade.

Background and Objective Antibiotics are widely used in veterinary and medicine in the last few decades which presence of these compounds has made potential risks for aquatic and terrestrial organisms in the environment. Metronidazole is one of these antibiotics. The purpose of this study was investigation of the efficiency of metronidazole removal from aqueous solutions using a catalytic ozonation process with magnetic nanoparticles of iron oxide doped with silica and titanium dioxide. Materials and Methods The sol gel method was used to synthesize Fe3O4@SiO2@TiO2 nanoparticles and its properties were investigated by SEM، XRD and EDX analyzes. The effect of parameters such as pH، catalyst dose، reaction time، contaminant concentration، determining the mineralization and scavenger effect were investigated on the process performance. Changes in metronidazole concentration were determined by HPLC. Results According to the results of this study، pH =10 and catalyst dose of 3 g /l were obtained as optimum conditions and the removal efficiency increased with increasing of contact time and decreasing in the concentration of metronidazole. Results showed that the removal of metronidazole followed first degree model by this process. Rate of TOC was 86% under optimal operating conditions. Conclusion Catalytic ozonation process with magnetic nanoparticles of iron oxide doped with silica and titanium dioxide can significantly remove metronidazole and it is an appropriate method for removal of metronidazole.

Background and Objective: With increasing water pollution, serious water shortages and increased pressure to save water, recycling and reuse of water has attracted more attention in various industries. Removal of silica from cooling water is essential for recycling and reuse of water. The aim of this study was to remove silica from water using magnesium oxide nanoparticles (MgO) synthesized by chemical deposition method. Materials and Methods: Synthetic nanoparticles were successfully determined using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD). To determine the optimal adsorption conditions the batch system, the effect of important parameters such as pH (2-8), contact time (0-150 min), initial concentration of silica solution (50-1000 mg/L), adsorbent amount (0. 01-0. 14 g) and temperature (25-60 ˚ C) were studied. Results: Under optimal conditions, an almost removal of 200 mg/L silica solution was achieved in 60 min reaction time. Equilibrium data were analyzed using the Langmuir and Freundlich isotherms. The adsorption process can be well described by the Langmuir model, and the maximum adsorption capacity was calculated as 75. 76 mg/g. Synthetic data were analyzed using pseudo-first-order and pseudo-second-order equations. The pseudo-second-order model showed good agreement with the obtained data (R2 = 0. 9949). Conclusion: Due to the high potential of magnesium oxide nanoparticles in silica removal, it can be a good candidate for the removal of silica and industrial wastewater treatment.