Removal of Trichloroethylene from water by adsorption on to multiwall carbon nanotubes

Groundwater recourses may be contaminated with trichloroethylene [TCE] which is used in electronic, electric, dry cleaning and other similar industries and often treated by air stripping, which TCE in its vapor form is stripped from groundwater by air and is emitted into the atmosphere without any additional treatments. Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. In this study adsorption of trichloroethylene on multiwall carbon nanotubes has been investigated. The effect of contact time, pH, initial concentration of trichloroethylene and temperature on its adsorption were investigated. Adsorption isotherms and related constants were also determined. Results showed that contact times to reach equilibrium changed from 30 min [for 150 microg/L initial concentration] to 10 min [for 600 microg/L concentrations] at 25 [degree sign]C; the equilibrium times in 40[degree sign] C were 40 min and 15 min, respectively. Multi-wall carbon nanotubes showed to act as a good adsorbent for TCE in a wide range of pH=[3-9]. For pH>9, adsorption decreased due to ionization of oxygen-containing groups. Adsorption test results revealed that TCE adsorption on the studied adsorbents could be better described by Freundlich isotherm

Survey on degradation rates of trichloroethylene in aqueous solutions by ultrasound

Sonochemical degradation of different compounds such as chlorinated aliphatic hydrocarbons is one of the recent advanced oxidation processes and it may be effective for removing low concentration organic pollutants from aqueous streams. Trichloroethylene [TCE] is one of these compounds that is mainly used as a degreaser. Important studies about TCE sonolysis have been focused at millimolar levels and natural pH, but in this study the ultrasonic degradation of TCE at different micromolar initial concentrations [30, 300 and 3000 micro g/L] and 4 different initial pH with a 35 kHz frequency was investigated. Furthermore, the degradation of TCE by ultrasound with different concentrations of hydrogen peroxide at pH= 7 was also performed. Gas chromatography with FID detector was used for analyses of TCE. Results showed that the degradation of TCE increased with decrease in the initial concentration of TCE from 3000 to 30 micro g/L at all initial pH. Initial pH of solution and different concentrations of H[2]O[2] did not affect significantly the TCE destruction

Methyl tert-butyl ether adsorption on surfactant modified natural zeolites

Surfactant-modified clinoptilolite-rich tuff was used for the removal of methyl tert-butyl ether [MTBE] from aqueous solutions. Clinoptilolite zeolite from Miyaneh region of Iran was treated with sodium chloride and then modified with hexadecyltrimethylammonium chloride [HDTMA-Cl] and n-Cetylpyridinium bromide [CPB] to be used in different experimental conditions. The ability of raw or Non-Modified Zeolite [NMZ] and Surfactant-Modified Zeolites [SMZ] to remove MTBE from aqueous solutions was investigated as a function of contact time, pH and concentrations of adsorbent and adsorbate, by using a batch technique in aqueous system. The removal of MTBE from aqueous solutions by modified zeolites seemed to be more effective than non-modified samples. Also, HDTMA-modified zeolite had more effective performance than CPB-modified zeolite. The adsorption efficiency of MTBE onto SMZ[S] was found to increase by contact time and adsorbent concentrations, and by decreasing of pH and adsorbate concentrations. Empirical adsorption models of Langmuir and Freundlich were applied for the experimental data. Results showed that Langmuir isotherm was more suitable for this process. The experimental data fitted very well with the pseudo-second-order kinetic model. It was overally found that Surfactant-Modified Zeolites is an effective adsorbent for removal of methyl tert-butyl ether from contaminated solutions

[Microbiological and chemical quality of water in food industries with low content of water]

In the production of some high-consumed food products like cake, biscuit, chocolate and spaghetti water is used in the preparing of primary material and in the kneading processes. At the present study microbiological and chemical quality of consumed water in food industries of East Azerbaijan Province were studied. Eleven factories with different products were selected. Water samples were collected and analyzed regarding the microbiological contamination and chemical parameters, and heavy metals. In addition, condition of water quality in selected industry was surveyed during the summer. According to the results, monitoring of water quality in the studied industries is not suitable. The chemical characteristics of consumed water in those industries had major differences. Ni, Cr, Zn, Fe and Mn were present in all analyzed water but in lower concentration than national Maximum Contaminant Level [MCL]. Pb was measured in higher concentration than MCL in spaghetti factory no. 2 and close to MCL in wiener and frankfurter and sugar industries. Cd was close to MCL in spaghetti factory no. 2 and wiener and frankfurter industries. It was concluded that for the safety and health of food products the food industries should use the public water supply system as water source at least in food processing units or in the units of preparing of primary materials. Also for the preventing of chemical pollution of food products it is necessary, pay more attention to the subject of water quality control according to the special water standard of food industries, and using less volume of water in some food industry isn.t acceptable reason for neglecting of water quality monitoring and assessing. In addition it is required to analyze heavy metals in the final products of those industries

Removal of cadmium from industrial effluents by electrocoagulation process using iron electrodes

The object of this study is the evaluation of cadmium removal from industrial wastewater by electrocoagulation process. For this study a glass tank in 1.56 L volume with four plate electrode was used to do experiments. The electrodes made of iron and connect to the positive and negative pole of DC power supply [bipolar mode]. The tank was filled with synthetic wastewater that was containing cadmium ion in concentration 5, 50 and 500 mg/L and then it was started up. The percent of cadmium ion removal was measured at pH 3, 7 and 10 and in electric potential range of 20, 30 and 40 volts. At the end of each stage of experiment, volume of produced sludge was measured. The results obtained at different electrical potential showed that initial concentration of cadmium can effect on efficiency removal and for higher concentration of cadmium, higher electrical potential or more reaction time is needed. On the other hand, if the initial concentration increases, the time required of process should increase too. The final pH for iron electrodes was always higher than initial pH. As expected, the results showed that for a given time, the removal efficiency increased significantly with increase of current density. The highest electrical potential [40V] produced the quickest treatment with >99% cadmium reduction occurring after only 20 min. The result showed that, in this process, the use of different electrical potentials can provide a wide range of pH for doing this process and electrocoagulation process [using iron electrodes] is a reliable, safety, efficient and cost-effective method for removal of cadmium from industrial effluents, especially designed for pH =10 and voltage = 40V

Effect of organic loading on the performance of aerated submerged fixed-film reactor [ASFFR] for crude oil-containing wastewater treatment

An aerated submerged fixed-film [ASFF] bioreactor was developed to treat an artificial wastewater based on crude oil. Bee-Cell 2000 was used as support media having porosity of 87% and a specific surface area of 650 m[2]/m[3]. The system was able to achieve 83.14-97.05 percentage removal efficiencies of soluble chemical oxygen demand [SCOD] in the organic loading rate range of 0.84 to 9.41 g SCOD/m[2]day showed that the effluent SCOD concentration ranged between 18.93 and 100.93 mg/L at organic loadings experienced. Therefore, an ASFF process showed that it was feasible to treat high oily wastewater in order to meet the discharge standards

Removal of chromium [VI] from aqueous solution by Ulmus leaves

The Cr [VI] adsorption characteristics of Ulmus leaves [UL] and their ash were examined as a function of contact time, initial pH, and initial metal ion concentration. Batch adsorption experiments were performed. The effects of Ca[2+], Mg[2+], Na[+]and K[+] on adsorption were studied. Maximum removal was achieved in the pH=7, contact time of 60 minutes and with initial Cr [VI] concentration of 2 mg/L. Because at pH>/=6.5, precipitation of chromium may take place, optimum pH was selected at 6. Maximum adsorption rate values were found at the first 60 min at pH=6. The effect of the adsorbent on COD removal from aqueous solution showed that 2g/L of adsorbent caused 130 and 75 mg/L increase in COD of deionized water in 60 min for UL and its ash, respectively. The chromium adsorption data obtained under the optimum condition were described by the Langmuir and Freundlich isotherms. Studies showed that the Langmuir adsorption model better fitted than Freundlich, with R[2]>0.99. Also UL ash was more efficient than living leaves in removing chromium from aqueous solution

Kinetic and equilibrium studies of lead and cadmium biosorption from aqueous solutions by Sargassum SPP. Biomass

Contamination of the aqueous environment by heavy metals is a worldwide environmental problem. Biosorption of lead [11] and cadmium [II] from aqueous solutions by brown algae Sargassum spp. biomass was studied in a batch system. The heavy metals uptake was found to be rapid and reached to 88-96% of equilibrium capacity of biosorption in 15min. The pseudo second-order and saturation rate equations were found in the best fitness with the kinetic data [R2 > 0.99]. The data obtained from experiments of single-component biosorption isotherm were analyzed using the Freundlich, Langmuir, Freundlich-Langmuir and Redlich-Peterson isotherm models. The Redlich-Peterson equation described the biosorption isotherm of Pb2+ and Cd2+ with high correlation coefficient [R2 > 0.99] and better than the other equations. The effect of Na+, K+, Mg2+ and Ca2+ on the biosorption of Pb2+ was not significant, but the metal ions affected the biosorption of Cd2+ considerably. According to the Langmuir model, the maximum uptake capacities [q m] of Sargassum spp. for Pb2+ and Cd2+ were obtained as 1.70 and 1.02mmol/g, respectively. Although the Sargassum spp. used in this study can be classified as an efficient biosorbent