Search

The goal of this paper was to evaluate the effectiveness of solar photo-Fenton (Fe2+/H2O2/UV–vis) treatment that is able to degrade heavy metal contents (Cu, Cd, Cr, Fe, Ni, Pb and Zn) and pathogenic microbial population (Fecal Coliform/100 mL) present in municipal wastewater with minimal iron and H2O2 concentrations. Photo-Fenton experiments were performed in a solar parabolic trough reactor (PTR). Three level factorial design and response surface method (RSM) was used for characterization and optimization of the process in which a response of interest is influenced by four key variables (pH, solar exposure time, catalyst dose (Fe2+/Fe3+), and amount of oxidant (H2O2)). The performance of advanced oxidant process was investigated in terms of percentage degradation of heavy metals and Fecal Coliform (FC) bacteria present in municipal wastewater. The result shows that variables have significant effect on the degradation process of municipal wastewater. Photocatalytic degradation efficiency was found to be dependent on optimized catalyst dose (Fe2+ 100 mg/L) and amount of oxidant (H2O2 500 mg/L). Analysis of variance (ANOVA) exhibited a high coefficient (R2 = 0.72–0.89), thereby indicating a satisfactory fit between the experimental results. The statistical model of solar photo-Fenton has shown excellent performance. Excessive hydrogen peroxide and iron have shown scavenging effects on hydroxyl radicals and reduced degradation of micro-pollutants present in wastewater. © 2016 American Institute of Chemical Engineers Environ Prog, 2016

In this study, municipal wastewater was treated by two types of advanced oxidation processes—photocatalytic (solar radiation/TiO2) and photocatalytic with oxidation (solar radiation/TiO2/H2O2). Response Surface Method (RSM) was used for characterization and optimization of both the processes in which a response of interest is influenced by several variables. The factors study includes pH, catalyst dose, and amount of oxidant. The performance of photocatalytic and oxidant process was investigated in terms of percentage degradation of wastewater. The result shows that catalyst dose and amount of oxidant have significant effect on the degradation process of municipal wastewater. Photocatalytic degradation efficiency was found to be dependent on optimized catalyst dose (1 g/L) and amount of oxidant (30 mL/L). Analysis of variance (ANOVA) exhibited a high coefficient (r2 = 0.912–0.996), thereby indicating a satisfactory fit between the experimental results. The statistical model of solar radiation/TiO2/H2O2 has shown excellent performance. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1629–1639, 2015

This article describes the photocatalytic reduction and deposition of four metal ions Cr(VI), Ni(II), Zn(II), and Cu(II) present in the wastewater from a chrome plating industry using solar energy irradiated TiO2. A parabolic trough reactor was used to carry out the reaction. Experiments were carried out to find an optimum dose of hole scavenger used (citric acid). The adsorption and reduction of the metal ions at different pH values was also investigated. It was observed that the solar photocatalytic process was effective in removing most of the metal ions in specific reaction conditions. Alkaline pH was found to be more suitable for removal of nickel and zinc. However, Cr(VI) reduced completely even at catalyst concentrations as low as 0.5 mg/L at pH 2. Maximum reaction was completed in the first 4 h of solar exposure. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

The present study is targeted on solar photocatalytic removal of metal ions from wastewater. Photoreductive deposition and dark adsorption of metal ions Cu(II), Ni(II), Pb(II) and Zn(II), using solar energy irradiated TiO 2 , has been investigated. Citric acid has been used as a hole scavenger. Modeling of metal species has been performed and speciation is used as a tool for discussing the photodeposition trends. Ninety-seven percent reductive deposition was obtained for copper. The deposition values of other metals were significantly low [nickel (36.4%), zinc (22.2%) and lead (41.4%)], indicating that the photocatalytic treatment process, using solar energy, was more suitable for wastewater containing Cu(II) ions. In absence of citric acid, the decreasing order deposition was Cu(II) > Ni(II) > Pb(II) > Zn(II), which proves the theoretical thermodynamic predictions about the metals.

A moving bed biofilm reactor (MBBR) coupled with solar parabolic structured system has been designed and developed to get the maximum organic load removal and microbial disinfection from the wastewater. The effluent was first subjected to organic degradation in MBBR (with optimized carrier filling rate of 30%) followed by the bacterial degradation using solar energy in parabolic trough and the changes in values of parameters like pH, turbidity, chemical oxygen demand (COD), bio-chemical oxygen demand (BOD) and microbial count were monitored. The titanium dioxide (TiO 2 ) was used as a photocatalyst for the removal of organic load from the wastewater but in optimized conditions. At optimum dose of 1.0 g/L of TiO 2 and pH value of 7.6, maximum COD removal of 69% and 13% was achieved at sunny days (solar irradiation 400–700 W m −2 ) and cloudy days (solar irradiation 170–250 W m −2 ) respectively within 5–6 h solar irradiation time. The results obtained showed that it is possible to decrease in six logarithms (log) the concentration of TC and FC within only 240 min of solar exposure. Moreover, this process can offer economically reasonable, chemical free and practical solution to the processing of municipal wastewater where solar intensity is readily available and can be used for making zero liquid discharge (ZLD) an effective reality.

A laboratory scale parabolic trough collector has been tested for photocatalytic reaction application to wastewater treatment under different reaction conditions. The photocatalytic reduction of Cr(VI) to Cr(III), using TiO2 suspensions under solar irradiation, has been investigated. The influence of reaction conditions has been illustrated using an organic additive (citric acid) in varying doses and also by performing the reaction at different pH values and doses of TiO2. An attempt has also been made to investigate the reuse performance of the photocatalyst. The rate of reduction was found to increase steadily with increasing concentration of organic additive, TiO2 dose and decreasing pH. Complete reduction of Cr(VI) to Cr(III) was achieved in 2 h and very low catalyst concentration at pH 2. The reuse studies showed that the catalyst can be used 2–3 times for lower Cr(VI) concentrations.

The present study is targeted on the effect of pH on solar photocatalytic removal of metal ions from wastewater. Photoreductive deposition and dark adsorption of metal ions Cu(II), Ni(II), Pb(II) and Zn(II), using solar energy irradiated TiO 2 , has been investigated at pH values 2, 4, 7, 8 and 10. Modeling of metal species at the studied pH values has been performed and speciation is used as a tool for discussing the photodeposition. The decreasing order of metal deposition at pH 2 and 4 was found to be Pb(II) > Cu(II) > Ni(II) ≅ Zn(II). In the neutral and alkaline pH conditions (pH 7, 8 and 10) the order was Cu(II) > Zn(II) > Ni(II) > Pb(II).

An attempt has been made to treat the wastewater containing a combination of inorganic contaminants to take the advantage of solar photocatalytic redox reactions. Synthetic wastewater is prepared containing substantial heavy metals to obtain a simultaneous reduction of both the wastewater components. The reaction is also attempted at different pH values to optimize the same. The metals in the waste combination are Cr, Ni, Zn, and Cu. Dark adsorption reactions are also performed along with the sunlight irradiation, in order to understand the process in detail. Results show that significant chromium and copper are the metals which are significantly reduced as compared to the other two metals studied. Chromium showed maximum reduced in the acidic pH range whereas the other metals were reduced in the alkaline and neutral pH ranges. The results provide a cost-effective method to remove organic and inorganic pollutants simultaneously in the simulated wastewater through photocatalytic.

There are great interests in photocatalytic oxidation of contaminants using advanced oxidation processes (AOP) based on photocatalytic oxidation in recent years. The main aim of the paper is to develop a method which takes care of energy and water conservation together. The study was performed on photocatalytic disinfection of total coliform (TC) bacteria as water microbial pollution and reducing the chemical oxygen demand (COD) as organic pollution index using catalytic and oxidant in present of sun light. The municipal wastewater was monitored for TC and in then was irradiated with solar light, solar light/TiO2, and solar light/TiO2/H2O2. Various parameters such as contact time, pH, and different concentration of TiO2 and H2O2 were studied for their effect on reaction process. The result showed that in presence of solar light, catalyst, and oxidant, very effective disinfection and reduction of TC and COD took place. 95.2% and 97% of TC and COD were reduced by irradiation for 240-300 min. Based on the re...

This study has focused on treatment of the metal ions, which have infinite lifetimes and build up their concentrations in food chains to toxic levels. Many researches have been performed about use of photocatalysis processes in treatment of industrial wastewater. The additional advantage is coming from sensitivity of the Cr(VI) photo reduction to the surface catalytic effects or to the presence of an additional electron donor and acceptors; then, a synergistic effect was observed in two- or multi-component systems. The efficiency of total chromium reduction by photo catalytic treatment under UV-light in different degradation systems, UV, TiO2/UV, H2O2/UV, TiO2/citric acid/UV, and TiO2/H2O2/UV, was studied and compared. Even when the TiO2/citric acid/H2O2/UV reaction happened to be the most efficient process, both homogeneous and heterogeneous photocatalysis can be considered as suitable methods to reach the complete mineralization of the solutions. Maximum treatment efficiency of total chromium reduction with increasing citric acid concentration from 20 to 80 mg/l was reduced to 62%, 76.7%, 77.91%, and 100%, and with increasing H2O2 concentration from 20 to 100 ml/l was reduced to 40.57%, 41.84%, 50.77%, 61.03%, and 100%, which is more efficient than the H2O2/UV process. Finally, the combination of TiO2/citric acid/H2O2/UV result was observed more efficient than the TiO2/citric acid and TiO2/H2O2/UV processes in the solutions.