behnoosh khataei

The increase in the number of factories, the industrialization of human life, and the increasing use of industrial paints have caused an increase in dye wastewater and consequent environmental pollution. Discharging wastewater containing the dyes mentioned above, which are often carcinogenic, is a severe threat to living organisms. In this research, a photocatalytic method (as an advanced oxidation method) using zinc oxide nanoparticles was investigated to treat the colored wastewater containing methylene blue. This type of nanoparticle is cheap (based on the used synthesis method), abundant and readily available, and low in toxicity. For this purpose, an evaluation of the optimal ratio between zinc acetate and polyvinylpyrrolidone for the synthesis of zinc oxide nanoparticles was carried out. Furthermore, the simultaneous decreasing and increasing effects of independent parameters (pH, irradiation time, methylene blue concentration, zinc acetate to PVP ratio) on the efficiency of the photocatalytic process and kinetic model were evaluated. The results showed that the best pollutant removal efficiency (91.7%) was obtained using the ratio of zinc acetate and polyvinylpyrrolidone equal to 33.67 in 60 minutes of irradiation time. This result shows that the lower ratio of zinc acetate to polyvinylpyrrolidone indicates higher dye removal.

Mining is one of the important economic activities all over the world. It causes the release of various emissions, especially heavy metals in the soil, due to the weak exploitation and improper disposal of mineral wastes. Different techniques are used for soil remediation and heavy metal extraction; including the electrokinetic method (so effective in fine-grained soils). In this research, the electrokinetic process was used to extract copper from the waste of the mine in Birjand.

In this research, a 24 cm long PVC reactor was used. The retention time was 2, 4, and 6 days and the voltage gradient was 1 V/cm. Graphite electrodes and electrolyte solutions of nitric acid and citric acid were investigated for copper extraction. The electrode polarity was alternately changed in order to pH control and improve the extraction process.

According to the results, the highest removal efficiency (54%) was obtained after 6 days using 0.1 M citric acid and distilled water in the anode and cathode reservoir, respectively. Further, by 24-hour polarity reversing, the copper removal efficiency increased to about 60%.

The use of citric acid in anode was more effective than nitric acid, leading to more copper removal. In addition, by periodically polarity change and keeping the soil pH in the neutral range, further dissolution of the metal and reducing its sedimentation in the soil occurred. As a result, the rate of its transfer outside the treatment area and removal efficiency increased.

Heavy metals are found in high concentrations in industrial wastewater and cause damage to humans and other organisms by entering to water, soil and food chain. Stabilization and solidification is a common process in the treatment of sludge containing heavy metals. In this study, solidification/stabilization of ceramic tile industry sludge was investigated using cement and additives like water, lime, microsilica and ordinary clay.

In this study, by designing the tests by response surface methodology, the effect of different additives on compressive strength and metals concentration after pollution leakage test was investigated. So, hazardousness of wastes after stabilization and solidification and the samples tolerance against the environmental loads was evaluated.

Results showed the highest value compressive strength in high amounts of cement. Decreasing the amount of waste and replacing more lime, clay and microsilica, the compressive strength was increased. In optimal mode, by 5.77% lime, 8.69% clay, 4.35% microsilica and 51.84% cement, the maximum compressive strength was achieved about 116 kg/cm2. The minimum concentration of Cr was 0.0782 mg/L and resulted from 11.23% lime, 21.31% clay, 10.65% microsilica and 27.46% cement. Minimum Pb concentration (0.0043 mg/L) was obtained in 11.23% lime, 21.31% clay, 4.35% microsilica and 33.76% cement.

The more efficiency on compressive strength is related to cement. In addition, applying the lime, clay, microsilica and cement concluded the effective reduction of Cr and Pb concentration in leaching the stabilized samples.

As (III) regularly requires oxidation to As (V), before it can be removed from water. Here, we reported photocatalytic removal of As (III) as well as adsorption of As (III) and As (V) using a novel, porous magnetic Ag/TiO2/Fe3O4@GO nanocomposite which was characterized via FT-IR, XRD, SEM, and TEM. A mathematical model (the central composite design) was used to estimate the relationship between the observed adsorption and our set of variables including initial concentration of arsenic ions, adsorbent dosage, pH, and the contact time. An optimum adsorption capacity of about 91% was observed for As (III) using 20 mg adsorbent with 24 ppm initial concentration of As (III), at pH = 5, within 90 min, and room temperature. Likewise, an optimum adsorption capacity of about 87% was observed for As (V) using 11 mg adsorbent with 17 ppm initial concentration of As (V), at pH = 3, within 30 min, and room temperature. The electrostatic factors between surface charge of nanocomposite and arsenic species were used to explain adsorption behavior of As (III) and As (V) at different conditions. The Langmuir isotherm equations best interpreted the nature of adsorption of As (III) and A (V). It was found during phocatalytic process maximum R% was about 63% for As (III) using 40 mg photocatalyst.

Removal of petroleum hydrocarbons from contaminated soil using electrokinetic method or biological processes has been considered in recent century. The most limiting factors in the electrokinetic process are extreme changes in pH around the electrodes and non-polarity of some pollutants. On the other hand, the key factor of biological treatment is simultaneous presence of microorganisms, pollutants (carbon source of microorganisms), electron acceptors, and essential nutrients for microorganisms’ growth. But in fine-grained soils with low permeability, it is difficult to uniformly distribute bacteria, electron acceptors and nutrients, or making pollutants available for microorganisms. To solve these problems, bioelectrokinetic method is used to eliminate the limitations of both biological and electrokinetic processes in treatment of fine-grained soil contaminated with organic compounds. In this integrative approach, the biological method has a role in biodegradation of pollutants. Whiles, the electrokinetic process can direct and accelerate the transfer of pollutants and microorganisms. The aim of this study is determining the equations and conditions governing on bioelectrokinetic process in removal of crude oil from clayey soil. For this reason, the numerical method of FTCS finite-difference was applied for modeling the pollutant biodegradation and transmission in clayey soil under electric field. In order to develop and validate the model, the first step was to set up a bioelectrokinetic system in a laboratory scale. In this study, each test was conducted in cylindrical cell made of Plexiglas with the length and diameter equal to 55 and 5 cm respectively, for 35 days. They were performed in various conditions of pollution amount and electric field intensity in the presence of Pseudomonas Putida strain. On the other hand, after determining and combining the governing equations on the electrokinetic and biodegradation system, the numerical solution of the equation was coded using Matlab software. In suggested mathematical model, the parameters like initial concentration of crude oil, voltage gradient, time step and spatial step were assumed as variables and parameters related to reactor, soil and pollutant such as the length of reactor, soil porosity and tortuosity, ion mobility, diffusion coefficient and electroosmosis permeability coefficient were considered as constants. In continue, by comparison the result of numerical solution of the suggested model with the experimental results, the same trend was observed in changes in crude oil concentration between the two. Because of differences between the model results and laboratory data and to make more accordance between the two, the modifying factor was used as the factor of microorganism transfer under electric field. In this way, by addition of modifying coefficient in model, a better accordance between them was observed and this difference reduced to minimum. Modeling results showed that electroosmosis, diffusion and electromigration mechanisms, unlike biodegradation, had little impact on the transmission and removal of oil from soil. According to the numerical solution, similar to bioelectrokinetic data, increasing the initial concentration of oil and voltage gradient caused the increase in removal efficiency of oil. In addition, the model has been able to predict the residual crude oil concentration after bioelectrokinetic treatment with a good accordance.