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Background and Objectives: Humic substances belong to a group of micro molecular of organic substance with different molecular weight produced by reaction of biological and geochemical process. They are known as one of the main prefabrications of disinfection byproducts. This study aimed at investigating the efficacy of (ZnO) nanoparticle under UV/ZnO radiation in removing humic acid. Material and Methods: This study was conducted under laboratory condition. An interval reactor was used to eliminate humic acid by (ZnO) nanoparticle and UV lamp (125 W Philips HPLN). The humic acid was considered in 2, 5, 7 and 10 mg/lit concentrations. To measure the residue of humic acid after radiation of photo Photocatalytic, Spectrophotometer model (UV/VIS Lambda 25 Perkin Elmer, Shelton) was used. Results: The results showed a decrease in efficiency rate when humic acid concentration and pH increased. By increasing the time of photocatalytic activity the removal effect increased. Also, we observed that single-step process and two-step process with higher removal efficiency at Zno concentration of 0.2 mg/l and 0.5 mg/l, respectively. The two-step process was found more capable of removing humic acid with 98.95% efficiency at the concentration of 0.5 mg/l ZnO, detention time of 30min, and at pH 4. Conclusion: This study suggests the use of UV/ZnO process as a suitable method in removing humic acid from aqueous solutions.

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Background and purpose: Natural organic matter in water resources (mainly caused by humic acid) leads to formation of THMs and HAAs. Removal of DBPs precursors from drinking water resources is the most important step to prevent from THMs formation. The aim of this study was to investigate the efficiency of modified nanoclay with EDTA and fresh nanoclay in adsorption of humic acid in aquatic solutions.

Materials and methods: Characteristics and chemical structure of fresh and modified nanoclays were determined via scanning electronic microscope (SEM), BET, XRD, and FTIR techniques. HA concentration was determined by spectrophotometric method in 254 nm. Langmuir, Freundlich models and pseudo-first and pseudo second-order kinetics were used for adsorption isotherm and kinetics studies, respectively.

Results: The XRD results showed that the distance between the layers increased after modification of nanoclay with EDTA. Also, BET analysis revealed that specific area of nanoclay increased from 13.02 to 28.36 m²/gr after modification. By decrease in pH the efficiency in removal of humic acid increased and in constant initial concentration of HA by increasing adsorbent dosage the adsorption capacity decreased. Adsorption of HA onto modified nanoclay and fresh nanoclay complies with Langmuir (R²=0.989) and Freundlich (R²=0.96), respectively. The pseudo-first order kinetic complies for both adsorptions.

Conclusion: This study showed that in acidic condition the modified nanoclay has an appropriate efficiency on HA adsorption.

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Background and purpose: Trihalomethanes and haloacetic acids are formed through chlorination of waters containing natural organic matters and pose potential health problems. So, it is necessary to remove humic acid as the most significant natural organic matter in water. The aim of this study was to evaluate the efficiency of catalytic ozonation in removal of humic acid in presence of local green and red montmorillonite.

Materials and methods: Green and red soils were collected from Sarcham area in Ardabil, Iran and used as catalysts after cleaning up. The variables in this study included initial pH of the solution, catalyst dosage, reaction time, and initial concentration of the pollutant.

Results: The efficiency of catalytic ozonation process increased by increase in contact time, pH, and doses of catalysts and also by decrease in initial concentration of humic acid. In COP process, 100% removal of humic acid (10mg/l) was achieved at natural pH in 15 and 20 min in presence of green and red soils, respectively. Compared with conventional ozonation, presence of radical scavengers such as nitrate, chloride, sulphate and carbonate at high concentrations were found to have minor effects on reducing the efficiency of catalytic ozonation process.

Conclusion: Based on this study, green and red soils highly increase the efficiency of catalytic ozonation process. Due to the low cost and availability of these soils, they can be used as catalysts to remove humic acid in catalytic ozonation process or other similar processes.

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Background and purpose: Presence of natural organic substances in surface water supplies could be harmful and have adverse effects on drinking water treatment due to many practical and hygiene reasons. This study aimed at investigating the efficiency of catalytic ozonation process in removal and mineralization of humic substances in water resources in north of Iran.
Materials and methods: Water treatment plants in Gorgan and Sari were studied (2017). First, the concentration of humic substances was measured in water. Then catalytic ozonation process (COP) of the water samples were performed using semi-continuous cylindrical reactor. The effects of some parameters such as reaction time (0-60 min) and catalyst dosage (0 and 3 g/L) on removal efficiency and mineralization of humic substances were investigated. After determining the kinetics constants of reactions, the removal efficiencies were compared between COP and single ozonation process (SOP).
Results: The concentrations of humic substances in water samples in Sari and Gorgan were 15.22 ± 5.39 and 18.62 ± 6.16 mg/L, respectively. The efficiency of removal of humic acid and its mineralization in the COP process under optimal conditions for Naharkhoran, Sari Salim Bahram, and Alangdare water treatment plants, were 100, 84.21, 88.18%, and 100, 83.4, and 78.03%, respectively. The reaction kinetics were first-order and their rates were 2.6, 2.9, and 3.7 folds more than those of the COP process, respectively
Conclusion: Using magnetic activated carbon catalyst coupled with ozonation process, compared to SOP, is 40% more efficient in removal of humic substances. Also, by reducing the ozonation time and the easy recovery of the catalyst and improving the process efficiency it reduces the costs.