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Monoaromatic hydrocarbons including benzene, toluene, ethylbenzene and xylene isomers (BTEX) are a very important category of water pollutants. These volatile compounds are very hazardous because of their fast migration in soil and water bodies and their acute and chronic toxicities when inhaled or ingested, especially benzene which is a known carcinogenic molecule. In this study, a natural zeolite (i. e., clinoptilolite-rich tuffs) was modified by two cationic surfactants (i. e., hexadecyltrimethyl ammonium chloride (HDTMA-Cl), and N-cetylpyridinium bromide (CPB)). The prepared adsorbents were then characterized, and their adsorptive capabilities for BTEX examined at different experimental conditions. The results of adsorption tests at 24 h revealed that the adsorption capacity of the modified zeolites improved by increasing the surfactant loading (i. e., less than the critical micelle concentration (CMC), to higher than the CMC), which caused an increase in sorption capacity from 60 to 70% for HDTMA-modified samples, and from 47 to 99% for CPB-modified zeolite. Adsorption kinetic tests showed the optimum contact time was 48 h with an average BTEX removal of 90 and 93% for HDTMA-modified and CPB-modified zeolite, respectively. Results showed that by increasing of pH from 3 to 11, the sorption capacity of the adsorbent decreased markedly from 97 to 75%. Analyzing the influence of temperature showed that the adsorption efficiency of adsorbents for benzene reduced from 93% at 208C to 10% at 48C. However, the influence of temperature on other compounds was not remarkable. Overall, CPB-modified zeolite exhibited higher selectivity toward BTEX compounds at optimum experimental conditions. Although commercial powder activated carbon (PAC) showed a higher capacity for all BTEX compounds and faster adsorption kinetics, the adsorption capacity of the CPB-modified zeolite at optimized conditions was competitive with PAC results.

BACKGROUND: The present study describes an electrocoagulation process for treating laundry waste-water using aluminum plates. The effect of various parameters such pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated.

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This research evaluates the lifetime cancer risks from trihalomethanes in Tehran's drinking water. The Trihalomethanes were measured in seven different water districts. Sixty-three samples were taken from tap water across the city for 7 months. The samples were analyzed for trihalomethanes using US EPA method 524.2. The average concentration of total trihalomethanes in different districts were between 0.81 and 9.0 μg/L, and the highest concentrations were detected in district 2 at 19.5 μg/L. Total lifetime cancer risks assessment from exposure to trihalomethanes in drinking water (ingestion, inhalation, and skin routes) were performed for people living in different districts in Tehran. The lifetime cancer risk was 7.19 × 10(-5) in district 2 (a more affluent neighborhood) where mostly surface water sources is used to supply drinking water and 9.38 × 10(-6) in district 7 (a less affluent neighborhood) which is mainly supplied with well water sources. Based on the population data, the total expected lifetime cancer cases from exposure to trihalomethanes are 104, 108, 81, 81, 41, 27, and three for districts 1 through 7, respectively. The average lifetime cancer risk was 4.33 × 10(-5) which means a total of 606 lifetime cancer cases for the entire province of Tehran. The highest risk from THMs seems to be from the inhalation route followed by ingestion and dermal contacts.

Increasing release of organic pollutants to the environment has caused one of the largest world crises for water resources. Volatile organic compounds are toxic monoaromatic pollutants of soil and water. In this research, natural zeolite nanoparticles were produced mechanically by means of a milling technique, modified using two cationic surfactants of hexadecyltrimethylammonium chloride and n-cetyl pyridinium bromide and formed as granules using a novel technique already developed by our group. The granulated adsorbents were used to uptake benzene, toluene, ethylbenzene, and xylenes (BTEX) from contaminated water. Two intra-particle diffusion models (i.e., Weber and Morris and Vermeulen models) and three surface reaction models (i.e., pseudo-first order, pseudo-second order, and Elovich) were applied to evaluate the kinetics of adsorption and the best fitted model was chosen. Results of the adsorption kinetic evaluations were shown that uptake of granulated nanozeolites are higher than natural zeolites (in the order of four). Kinetic results revealed that the adsorption follows a pseudosecond order indicating existence of chemisorption in the studied conditions. It was noticed that the intraparticle diffusion is prevailing in the first stage of adsorption for a relatively short time (i.e., first 25 min).

Pharmaceutical compounds, widely produced and used all around the world, are partly responsible for the widespread water pollution in the environment. Carbamazepine (CBZ) is an antiepileptic drug that persists in the environment for many years. In the present study, we used the TiO2/UV, nanoparticulate zero‐valent iron (NZVI), and NZVI/H2O2 treatment processes to compare efficiency of CBZ removal from water. Influence of NZVI loading, H2O2 concentration, TiO2 loading, UV lamp power, and the matrix (distilled water and groundwater) on CBZ removal efficiency was evaluated using full factorial design. Results indicated that the NZVI/H2O2 process oxidized CBZ within 5 min. On the other hand, the NZVI process alone did not reduce CBZ concentration after 120 min of process time. The NZVI/H2O2 process was equally effective in CBZ removal from both distilled water and groundwater whereas the TiO2/UV process was less effective due to the presence of ions in groundwater. CBZ removal efficiency of the TiO2/UV process declined 30% when the matrix was changed from distilled water to groundwater. Negative divalent ions, i.e., ${\rm SO}_{{\rm 4}}^{{\rm 2}- } $ and ${\rm CO}_{{\rm 3}}^{{\rm 2}- } $, were the main cause of reduction of CBZ removal efficiency from groundwater. It is likely that these two ions adsorb onto, and consequently prevent the superoxide anion ${\rm O}_{{\rm 2}}^{\bullet - } $ and hydroxyl radical OH• from being generated on, the surface of the TiO2.