Maximum Chemical Oxygen Demand Removal Efficiency Research Articles

Synthesis and characterization of carbon xerogel based iron catalyst for use in wet air oxidation of aqueous solution containing 2, 4, 6–trichlorophenol

Carbon xerogels were prepared using tannic acid, resorcinol and formaldehyde as precursors. The water content of the wet organic xerogels was replaced with t-butanol as a solvent to prevent pore collapse during ambient drying and the carbon xerogels were modified using o-phosphoric acid to improve its surface and textural properties. The xerogels and the carbon xerogel based iron catalyst were characterized for surface, textural and physico-chemical properties using various techniques. The catalytic wet air oxidation (CWAO) of aqueous solution containing 2, 4, 6-trichlorophenol (TCP) was performed using modified carbon xerogel based iron catalyst and the results were interpreted in terms of TCP and chemical oxygen demand (COD) removal efficiencies. The effect of various operating parameters on the TCP and COD removal efficiencies was studied and the maximum TCP and COD removal efficiencies of 74.49% and 24.31%, respectively were obtained at the optimum value of operating parameters. The kinetics of the degradation of TCP was studied. The reusability of the catalyst was explored by repeating CWAO experiments three times with washing and thermal treatment of used catalyst after each cycle. The leaching of iron metal from the catalyst was studied by determining the iron metal content in the CWAO effluent.

COD removal from disperse blue dye 79 in wastewater by using Ozone-Fenton process

Nowadays, one of the major problems that can face humankind is the water pollution. In this regard, making this natural resource a fresh and unpolluted is a major social and economic concern. However, a great attention has been given for the removal of organic pollutants discharged within wastewater by using advanced oxidation processes (AOPs) based on generation hydroxyl radicals. Among these, Ozone-Fenton (O3/H2O2/Fe2+) process used in this study as AOPs to remove chemical oxygen demand (COD) from Disperse Blue 79 (DB 79) dye in wastewater. Also, the effect of various experimental parameters such as ozone mass flow rate, mole ratio (mole H2O2/mole Fe2+), and reaction time on the COD removal efficiency of DB 79 were studied with constant initial concentration 60 mg/L of DB 79. Based on the results obtained in this study, the maximum COD removal efficiency was 85% achieved at optimum operating parameters are 288 mg/L. h ozone mass flow rate, 33.53 mole ratio (150 mg/L H2O2, 20 mg/L Fe2+), and 60 min reaction time. All Ozone-Fenton experiments were performed using Jar test apparatus at room temperature (23°C ∓ 2) and atmospheric pressure (1 atm). Finally, Ozone-Fenton offered an effective solution as AOPs for degrading pollutant especially DB 79 discharged within wastewater from various industrial processes.

Catalytic Ozonation of Biologically Treated Leachate from Municipal Solid Waste in a Microbubble Reactor

ABSTRACTCatalytic ozonation using activated carbon (AC) as catalyst for advanced treatment of biologically treated leachate (BTL) from municipal solid waste incineration plant was carried out in a microbubble reactor. The removal efficiency of chemical oxygen demand (COD) in the leachate was significantly improved over that in the conventional bubble reactor. The effects of AC dosage, ozone concentration, ozone flowrate and liquid reaction temperature on COD removal efficiency were studied. The results show that the COD removal efficiency increased with increasing AC dosage, ozone flowrate and inlet ozone concentration, and the reactor liquid phase temperature has little effects on the COD removal efficiency. The maximum COD removal efficiency reached 89.87% in the AC/O3 system under the optimal conditions. The catalytic activity of the AC still remained stable after five cycles of use. Ultraviolet-visible (UV-Vis) spectra and GC-MS analysis indicated that the AC-catalyzed ozonation can enhance the efficiency of the organic pollutants; the mechanism of AC deactivation was explored using the variation of AC-specific surface area and X-ray diffraction analysis. In addition, the regeneration of AC was proved effective by hydrochloric acid leaching. These results show that the combination of a microbubble reactor with AC provided a highly efficient ozonation process for the BTL.

Adsorption of sugarcane vinasse effluent on bagasse fly ash: A parametric and kinetic study

Sugarcane and bioethanol production produces large amounts of bagasse fly ash and vinasse, which are solid and viscous liquid wastes, respectively. However, these wastes are often disposed into the environment without treatment, thus posing an environmental and public health risk. This study investigated the treatment of vinasse effluent in terms of reduction of chemical oxygen demand (COD) and acidity removal using sugarcane bagasse fly ash. A maximum COD removal efficiency of 72% was obtained using an effluent volume of 100 mL, contact time of 180 min, and shaking speed of 240 rpm. The adsorbent dose and particle sizes were 4.5 g and 90–125 μm, respectively. Furthermore, the potential application of bagasse fly ash as an adsorbent in a sand filtration bed was assessed using a column test. A maximum recovery of 68% was obtained at the 25-min interval. The adsorption data was found to fit the Freundlich model best (Kf = 2.16 mg g−1; R2 = 0.96), and the kinetics fit the pseudo-second order model (R2 = 0.98).

Investigation of effective treatment techniques for Olive mill wastewater

Selection of cost-effective treatment modules for high saline wastewater produced from the olive mill is a challenging task. The aim of this study is to select the most effective technology applied to treat Olive mill wastewater. Several trials using various techniques were carried out to treat wastewater produced from pickling olives and olive oil manufacturing; for instance, anaerobic-aerobic, coagulation/flocculation, and electrocoagulation. The characteristics of olive manufacturing raw wastewater in terms of total dissolved solids (TDS), chemical oxygen demand (COD) and oil and grease were 10032, 9174, and 914.8 mg/l respectively. The results showed that electro-coagulation technique with aluminum electrodes and operating parameters of 30 voltage and 1.5 hours achieved COD removal rate 84%. However, the residual concentration (900 mgO2/l) still needs further treatment. Aerobic treatment using activated sludge was applied after electrocoagulation. The results showed that the use aerobic treatment after electrocoagulation is more efficient than the use of anaerobic. Analysis of the treated water showed that the maximum COD removal efficiencies were 98% at optimum conditions. The effluent quality meets the discharge regulatory standard. Consequently, the electrocoagulation followed by aerobic process can be considered as a reliable, safe and cost-effective method for the treatment of olive mill wastewater.

Optimization of electrocoagulation process and combination of anaerobic digestion for the treatment of pistachio processing wastewater

Abstract It is very challenging to treat raw pistachio processing wastewater (PPW) by one step process due to its high chemical oxygen demand (COD) and total phenols (TP). In this study, electrochemical (EC) process and anaerobic digestion are combined to improve treatment efficiency. Central composite design (CCD) was used in EC experimental design with three factors at three levels of the independent variables. Impact of current density (50─100 A/m2), electrode distance (2─6 cm), and reaction time (60─300 min) on the removal of COD and TP were systematically investigated. A maximum removal efficiency of 43.7 and 56.4% of COD and TP, respectively, was obtained with the current density of 100 A/m2, electrode distance of 6 cm, and reaction time of 293 min. Specific energy consumption (SEC) was measured as 7.80 kWh/kgCOD for the same experimental conditions. In order to achieve further treatment, a batch anaerobic reactor was combined with EC process to produce biogas. COD and TP removal efficiency were measured in the anaerobic reactors at appropriate time intervals (0, 10, 25, 30, 40, and 50th d) and biochemical methane potential (BMP) tests lasted up to 50 d. BMP enhancement of raw PPW was found as 35.7 and 16.5% for electrocoagulated PPW under maximum COD and TP removal efficiency condition (100 A/m2 current density, 6 cm electrode distance, and 293 min reaction time) and under cost driven approach condition (53 A/m2 current density, 2 cm electrode distance, and 182 min reaction time) compared to raw PPW. The results showed that pre-treated PPW with EC process had the highest COD and TP removal efficiencies and enhanced the biochemical methane production, by decreasing the concentration of total phenols in the PPW. Energy balance revealed that EC under cost driven approach condition combined with anaerobic digestion can be used as an energy positive process for the treatment of PPW.

Influence of various operating conditions on wastewater treatment in an AS-biofilm reactor and post-treatment using TiO2-based solar/UV photocatalysis

ABSTRACTIn the present study, the effect of carbon to nitrogen (C/N) ratio, suspended biomass concentration (X), hydraulic retention time (HRT) and dissolved oxygen (DO) on chemical oxygen demand (COD) and nutrient removal from wastewater was investigated in a lab-scale activated sludge (AS)-biofilm reactor. Furthermore, in order to improve the quality of the treated wastewater, photocatalysis by TiO2 was investigated as a post-treatment technology, using solar and UV irradiations. The AS-biofilm reactor provided a substantial removal efficiency in terms of COD, ammonia nitrogen , total nitrogen (TN) and total phosphorous when the system was maintained at C/N ratio 6.66, X in the range 2–2.5 g/L, HRT 10 h, DO in the range of 3.5–4.5 mg/L and organic loading rate (OLR) of 0.96 kg COD/m3 d during Run 1. Similarly, when the reactor was maintained at C/N ratio 10, X in the range of 3–3.5 g/L, HRT 8 h, DO in the range of 3.5–4.5 mg/L and OLR of 1.8 kg COD/m3 d during Run 2. The microstructure of suspended and attached biomass comprised a dense bacterial structure of cocci and bacillus microorganisms. The UV photocatalysis was found to be better than solar photocatalysis during the comparative analysis. The maximum removal efficiencies of COD, most probable number and phosphorous at optimum conditions in the case of UV and solar irradiations were 72%, 95%, 52% and 71%, 99%, 50%, respectively.

Simultaneous removal of atrazine and organic matter from wastewater using anaerobic moving bed biofilm reactor: A performance analysis

In this study, an anaerobic moving bed biofilm reactor (AMBBR) was designed to biodegrade atrazine under mesophilic (32 °C) condition and then it was evaluated for approximately 1 year. After biofilm formation, acclimation, and enrichment of microbial population within the bioreactor, the effect of various operation conditions such as changes in the concentration of influent atrazine and sucrose, hydraulic retention time (HRT), and salinity on the removal of atrazine and chemical oxygen demand (COD) were studied. In optimum conditions, the maximum removal efficiency of atrazine and COD was 60.5% and 97.4%, respectively. Various models were developed to predict the performance of atrazine removal as a function of HRT during continuous digestion. Also, coefficients kinetics was studied and the maximum atrazine removal rate was determined by Stover - Kincannon model (rmax = 0.223 kgATZ/m3d). Increasing salinity up to 20 g/L NaCl in influent flow could inhibit atrazine biodegradation process strongly in the AMBBR reactor; whereas, the reactor could tolerate the concentrations less than 20 g/L easily. Results showed that AMBBR is feasible, easy, affordable, so suitable process for efficiently biodegrading toxic chlorinated organic compounds such as atrazine. There was no accumulation of atrazine in the biofilm and the loss of atrazine in the control reactor was negligible; this shows that atrazine removal mechanism in this system was due to co-metabolism.

Nutrient removal from synthetic and secondary treated sewage and tannery wastewater through phycoremediation

ABSTRACTIn this study, potential microalgae species (Chlorella vulgaris, Scenedesmus dimorphus, Chlorococcum sp. and Chlamydomonas sp.) have been studied for nutrient removal from synthetic and industrial wastewater. Batch experiments were carried out to investigate the removal performance among four chosen species at different nitrogen and phosphorus concentrations. NH4-N and PO4-P were varied from 13.2 to 52.8 mg/L and 6.6 to 26.4 mg/L, respectively, by keeping N:P ratio as 2:1. In synthetic wastewater, maximum NH4-N and PO4-P removal efficiencies of 88.6% and 91.2% were obtained with C. vulgaris when compared to the other microalgae studied. Further studies were carried out using C. vulgaris in batch experiments to investigate the nutrient removal performance in secondary treated sewage, soak liquor and composite tannery effluent. Experimental results indicated that NH4-N, NO3-N, PO4-P and chemical oxygen demand (COD) removal efficiencies were found to be 68.6%, 74%, 71.5% and 90.2%, respectively, in secondary treated sewage. Maximum removal efficiencies of NH4-N, NO3-N, PO4-P and COD in composite tannery wastewater were found to be 55%, 85.6%, 60.5% and 43.4%, respectively. In soak liquor, maximum removal efficiencies of NH4-N, NO3-N, PO4-P and COD were found to 66.7%, 62.6%, 63.6% and 93.8%, respectively.

Effect of some effective parameters on COD Removal from Nam Son Landfill Leachate by electrocoagulation

Leachate becomes ahead of wastewaters as being the most difficult to treat due to its complex and widely variable composition. In this research, the leachate treatment performance by electrocoagulation (EC) was studied. The samples of leachate were taken from Nam Son landfill in Hanoi. The effects of factors namely current intensity, electrolysis time, initial pH and anode materials on the EC performance were investigated via chemical oxygen demand (COD) removal efficiencies. The input leachate properties were obtained as COD, NH4+ and pH in the range of around 6247 ± 295, 1270 ± 38 mg/l and 8 ± 0.1, respectively. Mono-polar electrocoagulation unit was carried out in a batch system for leachate treatment with iron electrodes and approximately 1.8 litter of leachate. Firstly, with the increase in current (1 to 4A), the COD removal efficiencies increased from 50.00 to 78.57% (pH = 8 and operating time = 40 min). Secondly, by the increase in operating time, the treatment performance also went up significantly in first 40 min, then nearly level-off at above 73 % (pH=8, current intensity = 3A). In addition, the effect of pH in range of 5 to 10 on the electrocoagulation process was studied and showed the highest treatment efficiencies in neutral and mild alkaline medium, especially between 6 < pH < 8. Finally, the electrode materials made of iron and aluminum was investigated and the result indicated that when the iron anodes were replaced by aluminum, the COD removal efficiency experienced a considerable decline, from 70 to 37.93% (pH = 8 and operating time = 40 min). In combination of all experiments, the optimum operating conditions were achieved as iron electrodes, current intensity of 3A, electrolysis time of 40 min, the raw pH with iron electrodes, resulting the maximum COD removal efficiencies of 73.21%. As a result, the electrocoagulation can be applied to leachate pre-treatment.

Treatment of Dairy Industry Cleaning‐in‐Place Wastewater by Electrocoagulation Supported with Immersed Membrane Process

This study aims to develop an easy and economic technique for dairy cleaning‐in‐place wastewater treatment to obtain high‐quality treated wastewater effluent. A batch electrocoagulation (EC) study is conducted using iron and aluminum electrodes. The effects of various operational parameters are investigated on the treatment performance. Maximum soluble chemical oxygen demand (COD) removal efficiencies of 81% for an Fe–Fe electrode and 53% for an Al–Al electrode are obtained at an applied voltage of 10 V, an electrode spacing of 2 cm, pH of 7.2, for a reaction time of 60 min. Moreover, protein removal efficiencies of 72.6 and 79.4% are obtained for Fe–Fe and Al–Al electrodes, respectively. An immersed membrane is integrated into the EC reactor and the reactor is operated in continuous mode. COD removal efficiency is determined as 86.4 and 84.5% for Fe–Fe and Al–Al electrodes, respectively, in continuous mode. The protein removal efficiency is also calculated as 80.9 and 83.8% for Fe–Fe and Al–Al electrodes, respectively. The Fe–Fe electrode shows the maximum COD removal efficiency, whereas Al–Al provides the maximum protein removal efficiency. Additionally, field emission scanning electron microscopy (FE‐SEM) and Fourier transform IR spectroscopy (FT‐IR) are applied to describe fouling phenomena.

Electrochemical degradation of psychoactive drug caffeine in aqueous solution using graphite electrode

ABSTRACTIn this study, the electrochemical degradation of caffeine (1,3,7-trimethylxanthine) in aqueous solution by a graphite electrode was investigated. Electrochemical degradation was tested by the cyclic voltametry technique performed in the potential range of −1.0 to +1.0 V versus Ag/AgCl, which confirmed the electro-activity of the selected caffeine. The effects of the treatment process variables, such as initial pH, current density, electrolyte concentration and electrolysis time on the degradation of caffeine, were explored. During the various stages of electrolysis, parameters such as chemical oxygen demand (COD), total organic carbon (TOC) were analysed. The maximum COD and TOC removal efficiencies of 85% and 77% were achieved at neutral pH 7, operated at a current density of 5.1 mA/cm2, electrolyte (Na2SO4) concentration of 0.1 M and at 240 min electrolysis time. From this study, it can be concluded that the electrochemical treatment process could effectively reduce the COD and TOC from the caffeine in aqueous medium. The degradation of the caffeine was confirmed by UV spectra, IR spectra and HPLC analysis.

Evaluation of Sequencing Batch Reactor Performance for Petrochemical Wastewater Treatment

Sequencing batch reactor (SBR) technology has found many applications in industrial wastewater treatment in recent years. The aim of this study was to determine the optimal time for a cycle of the sequencing batch reactor (SBR) and evaluate the performance of a SBR for petrochemical wastewater treatment in that cycle time. The reactor was operated with a suspended biomass configuration under aerobic conditions. Carbon removal and operating parameters such as pH, temperature and dissolved oxygen (DO) were monitored during the wastewater treatment. The SBR was run at different cycle times and amongst the cycle times tested, the best performance was obtained with a 7 h cycle time composed of a fill time of 15min, reaction of 6 h, settling of 30 min, and withdrawal of 15 min. The SBR with the determined cycle time was used to study the treatment of wastewater with various organic loading rates (12.88 gr COD/L.d, 18.02 gr COD/L.d and 31.39 gr COD/L.d). The SBR performance was evaluated by chemical oxygen demand (COD), total solids (TS) total suspended solids (TSS) removal efficiencies. During the shock loading tests, the maximum COD, TS and TSS removal efficiencies were 84%, 67% and 92%, respectively.

Optimization of hydroxyl radical production using electro‐Fenton method for chemical oxygen demand reduction in diluted palm oil mill effluent

AbstractPalm oil mill effluent (POME) is a well‐known highly polluting wastewater due to its extremely high contents of organic matter, suspended solids and nutrients. In this study, we used electro‐Fenton method to treat POME by optimizing OH• generation from hydrogen peroxide (H2O2) under low voltage input (1.5–6.0 V). A set of electro‐Fenton system was set up using stainless steel as the anode and graphite as the cathode. Four parameters namely retention times, concentrations of H2O2 as well as FeSO4 catalyst and applied voltages were studied. The results were reflected in the form of removal efficiency of chemical oxygen demand (COD). The optimum conditions to degrade organic matter in POME were found to be in 4 h retention time with the respective H2O2 and FeSO4 catalyst concentrations of 0.05 and 0.10 M, and the power input of 1.5 V. Under such conditions, the maximum COD removal efficiency achieved 94%. The electro‐Fenton treatment was found to have higher efficiency than the conventional Fenton treatment. Without the electrolysis, the COD removal efficiency of the conventional Fenton treatment was only 48%.

Treatment of highly acidic wastewater containing high energetic compounds using dimensionally stable anode

Highly acidic (pH < 2) wastewaters have toxic and carcinogenic properties and can’t be treated by conventional biological treatment methods. In the work presented, investigation of the treatment of very low pH, actual wastewater containing highly energetic materials was carried out using electro-oxidation method using a dimensionally stable anode (DSA) namely ruthenium oxide coated titanium (Ti/RuO2). Chemical oxygen demand (COD), current efficiency (CE) and specific energy consumption (SEC) were measured under various process conditions of current density (J) and time (t). Maximum COD removal efficiency of 41.83% was observed at J = 750A/m2, t=150min, and initial pH=0.4±0.1 with SEC=1.23kWh/kg COD. In the next phase, the addition of hydrogen peroxide (30%w/w) (H2O2) was done and COD degradation was evaluated by varying the dosage of H2O2. Maximum COD removal efficiencies of 48.83% was observed at J = 750A/m2, t=150min, pHo=0.3. This method produced very low or no amount of sludge and scum. The mechanistic study has been performed by carrying out scavenger study using terephthalic acid. Gas chromatography-mass spectroscopy (GC/MS), Fourier transform infrared spectroscopy and ion chromatography of the wastewater; and X-ray diffraction and Field emission scanning electron microscopy (FE/SEM) of electrodes were carried out for understanding the treatment mechanism. Operating cost analysis has been done based on the studies performed in laboratory scale EC reactor, and compared with those reported for other pollutant degradation.

Chemical Oxygen Demand and Turbidity Improvement of Deinked Tissue Wastewater using Electrocoagulation Techniques

The goal of this work was to evaluate the efficiency of electrocoagulation technique in deinked tissue industry wastewater. The effect of two types of electrodes, three electrolysis times, four voltages, and three pHs were investigated. Experiments were conducted in batch process using a glass cell. The chemical oxygen demand (COD) removal and turbidity improvement of wastewater were measured and evaluated through the independent and interaction effects of variables. The results revealed that both electrodes reduced the COD and turbidity. However, the ability of their performance depended on the electrolysis time, voltage, and pH. For COD, greater improvement by electrocoagulation technique was obtained with 45minute electrolysis time, 24 volts, and alkaline conditions, while the turbidity reduction was achieved at lower voltage. Analysis of the treated water showed that the maximum COD and turbidity removal efficiencies were 81.12% and 89.43%, respectively. The treated effluent was very clear, and its quality met the industrial applications. Consequently, the electrocoagulation technique can be considered a reliable and safe method for deinked tissue effluent treatments to replace the other chemical methods.

Bioelectricity generation and treatment of petroleum refinery effluent by &lt;i&gt;Bacillus cereus&lt;/i&gt; and &lt;i&gt;Clostridium butyricum&lt;/i&gt; using microbial fuel cell technology

Microbial fuel cells (MFCs) being an emerging technology have been the research focus of increasing interest due to their sustainable capacity for wastewater treatment together with electricity generation. This study investigated the potential use of pure culture Bacillus cereus and Clostridium butyricum as inoculums in MFCs for simultaneous bioelectricity generation and treatment of petroleum refinery effluent. Double-chambered MFCs was used for the study and operated over four-batch cycles for 30 cumulative days but with different external resistances. The influent concentrations of chemical oxygen demand (COD) and total organic compound (TOC) in the petroleum refinery effluent was 970 mg/l (ppm) and 156 g/l, respectively. Experimental results indicated that the MFCs with the use of Bacillus cereus as biocatalyst achieved its maximum COD removal, TOC degradation and coulombic efficiencies of 70%, 88.7% and 19.21%, respectively; while with the use of Clostridium butyricum, it achieved the highest COD removal, TOC degradation and coulombic efficiencies of 54.2%, 68.7% and 17.84%, respectively. A maximum voltage of 450 mV and highest power density of 17066.67 mW/m 2 with a maximum current density of 1.270 mA/m 2 was obtained in regard to the external resistor of 1000 Ω using Bacillus cereus as biocatalyst. Similarly, using Clostridium butyricum as biocatalyst the maximum voltage of 370 mV and highest power density of 8816.17mW/m 2 with a maximum current density of 0.913 mA/m 2 was achieved. The study demonstrated that both Bacillus cereus and Clostridium butyricum has strong potentials to be used as inoculums for simultaneous bioelectricity generation and treatment of petroleum refinery effluent in MFCs. http://dx.doi.org/10.4314/njt.v36i2. 30

Role of Micronutrients on Dyeing Wastewater Treatment in Activated Sludge Process.

Adequate individual supplements of Zn, Co and Mo increased chemical oxygen demand (COD) removal and specific oxygen uptake rates during activated sludge treatment of dyeing wastewater, while overdoses of micronutrients can decrease metabolic rates. The effects of combing Zn, Co, and Mo at different doses were investigated using response surface methodology, with a second order polynomial equation: Y = 78.19+ 0.17X1 + 37.33 X2 + 20.20X3 - 5.58X1X2 - 63.05 X2X3, where Y means COD removal rate (%), X1 means Co concentration, X2 means Zn concentration, X3 means Mo concentration. The maximum COD removal efficiency of 89.41% was achieved with doses of 0.02 mg/L Co, 0.24 mg/L Zn and 0.45 mg/L Mo. Both the combinations of Zn-Co and Zn-Mo acted antagonistically for COD removal efficiency, and the combination of Co-Mo was negligible to COD removal efficiency. Doses of micronutrients, particularly Zn, Co and Mo, were beneficial for microbial shift towards Planctomyces and Bacteroidetes.

Application of advanced oxidation process (H2O2/UV) for removal of organic materials from pharmaceutical industry effluent

Pharmaceutical wastewater is one of the major complex and toxic industrial effluents containing little or no biodegradable organic matters. In this study, H2O2AJV based advanced oxidation process (AOP) was used to remove organic materials from pharmaceutical industry effluent. For the chemical oxygen demand (COD) removal radiation of medium pressure mercury vapor UV lamp was used in the presence of hydrogen peroxide (H2O2/UV). Results indicated that the efficiency of COD removal depends on the initial concentration of H2O2, oxidation time and pH. The efficiency of COD removal at low H2O2 concentration was very low even coupled with UV light, which can be attributed to the low generation of hydroxyl radicals (OH·). At high concentration of H2O2 (500 mg/dm³) and optimum pH (pH = 4), 87.6% removal efficiency could be achieved during 70 min oxidation. For high concentration of H2O2 (500 mg/dm³) at pH 3 and 7, the maximum COD removal efficiency was 28.5% and 15.2% respectively, indicating significant roles of pH and H2O2 concentration in the process of COD removal. Application of advanced oxidation process (H2O2/UV) for removal of organic materials from pharmaceutical industry effluent. Available from: https://www.researchgate.net/publication/317775668_Application_of_advanced_oxidation_process_H2O2UV_for_removal_of_organic_materials_from_pharmaceutical_industry_effluent [accessed Jul 17, 2017].

Degradation of imidacloprid pesticide in aqueous solution using an eco-friendly electrochemical process

The aim of this study was to evaluate the efficiency of electrochemical degradation process in the removal of imidacloprid (IM), a pesticide, from aqueous solutions. Experiments were conducted using a batch glass reactor and two leads as anodes, and stainless steel electrode as a cathode. The influence of various experimental parameters including initial IM concentration (1–150 mg/L), pH (3–11), electrolysis time (20–120 min), current density (12.5–50 mA/cm2) and NaCl concentration (4.28–26.74 mmol/L) were assessed to determine the optimum conditions. Scanning electron microscopy and X-ray diffraction analyses were used to study the type of materials formed on the electrode surfaces at the electrode preparation stage. The results from this investigation show that at pH = 5, current density = 25 mA/cm2, electrolysis time = 30 min, initial pesticide concentration = 100 mg/L and NaCl concentration = 10.69 mmol/L are optimum experimental conditions for achieving maximum IM and chemical oxygen demand (COD) removal from water. Accordingly, the maximum IM and COD removal efficiencies of 99.69 and 85.66 were achieved, respectively. At optimum conditions and applied voltage of 23.95 V, the electrical energy consumption was calculated about 5.35 kWh/kg COD. Based on the results, electrochemical degradation method was found to be a highly efficient technology in comparison with existing conventional methods and could be considered as a cost-effective method to remove IM from water and wastewater. © 2017 Desalination Publications. All rights reserved.