Electrochemical Process for Diazinon Removal from Aqueous Media: Design of Experiments, Optimization, and DLLME-GC-FID Method for Diazinon Determination

In the present study, electrochemical process was studied via removal of diazinon (O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) as an insecticide/ acaricide organic case study. Influences of three operational parameters including initial ferrous ion concentration, initial hydrogen peroxide concentration, and initial diazinon concentration were measured and optimized in diazinon removal process. Response surface methodology (RSM) was used to design the experiments. The experimental data collected in a laboratory-scaled batch reactor equipped with four graphite bar electrodes as cathode and an aluminum sheet electrode as an anode. Quantitative analysis of diazinon was done with gas chromatography equipped with flame photometric detector. Disperse liquid–liquid microextraction was used prior to gas chromatography in order to extraction and preconcentration of diazinon from aqueous media to extraction phase. Acetone and chlorobenzene were used as disperser and extraction solvent, respectively. Maximum diazinon removal efficiency of 87% (0.85mg mass removal) in C0 of 2mg/L and 80% (120mg mass removal) in C0 of 300mg/L was achieved under different experimental conditions. The obtained experimental data were used for model building by RSM approach. Finally, optimization process was carried out using RSM algorithm. © 2015, King Fahd University of Petroleum & Minerals

A Novel Integration of CWPO Process with Fe3O4@C and Sonication for Oxidative Degradation of 4-Chlorophenol

This current work deals with oxidative destruction of 4-chlorophenol (4-CP) with catalytic wet peroxide oxidation (CWPO) using Fe3O4@C and sonication (US) in aqueous solution. The Fe3O4@C catalyst was synthetized and characterized with Field Emission Electron Microscopy and X-Ray Diffraction. Effect of operational variables, including initial pH, catalyst dosage, H2O2 concentration, 4-CP concentration, and sonication were investigated. A removal efficiency of 99 % was obtained by the CWPO/US-Fe3O4@C process in selected conditions including pH 5, Fe3O4@C dosage of 0.8 g L–1, H2O2 concentration of 20 mM, sonication power of 300 W, and reaction time of 60 min. Results indicated significant 4-CP removal with CWPO/US-Fe3O4@C (99 %) compared to CWPO (67 %) and US (10 %). According to the results, Fe3O4@C nanocomposite can be considered a cost-effective catalyst since it demonstrated acceptable reusability performance in degradation of 4-CP by CWPO/US-Fe3O4@C process. This work is licensed under a Creative Commons Attribution 4.0 International License

Comparison of AOPs Efficiencies on Phenolic Compounds Degradation

In this work, a comparison of the performances of different AOPs in the phenol and 4-chlorophenol (4-CP) degradation at lab and pilot scale is presented. It was found that, in the degradation of phenol, the performance of a coupled electro-oxidation/ozonation process is superior to that observed by a photo-Fenton process. Phenol removal rate was determined to be 0.83mg L−1 min−1 for the coupled process while the removal rate for photo-Fenton process was only 0.52mg L−1 min−1. Regarding 4-CP degradation, the complete disappearance of the molecule was achieved and the efficiency decreasing order was as follows: coupled electrooxidation/ ozonation > electro-Fenton-like process > photo-Fenton process > heterogeneous photocatalysis. Total organic carbon was completely removed by the coupled electro-oxidation/ozonation process. Also, it was found that oxalic acid is the most recalcitrant by-product and limits the mineralization degree attained by the technologies not applying ozone. In addition, an analysis on the energy consumption per removed gram of TOC was conducted and it was concluded that the less energy consumption is achieved by the coupled electro-oxidation/ozonation process

Integrated Treatment of Saline Oily Wastewater Using Sono-Electrokinetic Process, Degradation Mechanism, and Toxicity Assessment

Integration of sonication (US) with electrokinetic (EK) oxidation was studied for the treatment of a saline oily wastewater, as well as the effect of operating parameters, including pH, voltage, electrode distance (ED), sonication power, and reaction time on COD removal. A COD removal of 98 % was observed for the sono-electrokinetic (SEK) process with an applied voltage of 2.5 V, US power of 300 W, initial COD concentration of 3850 mg L–1, and reaction time of 9 h. The efficiency of SEK over sonication alone and EK oxidation alone was also confirmed with a higher pseudo-first-order reaction rate constant of 0.43 h–1, compared to values of 0.13 and 0.01 for alternative processes. In addition, the biodegradability of effluent was improved based on average oxidation state (AOS) and carbon oxidation state (COS) analysis. Oxygen consumption rate inhibition, dehydrogenase activity inhibition, and growth rate inhibition methods demonstrated the low toxicity of effluent (12–15 %) compared to influent. The current work indicated that SEK is a reliable and efficient technology for the treatment of saline oily wastewaters containing recalcitrant aromatic organics. This work is licensed under a Creative Commons Attribution 4.0 International License

Fe-chitosan complexes for oxidative degradation of emerging contaminants in water: Structure, activity, and reaction mechanism

Versatile and ecofriendly methods to perform oxidations at near-neutral pH are of crucial importance for processes aimed at purifying water. Chitosan, a deacetylated form of chitin, is a promising starting material owing to its biocompatibility and ability to form stable films and complexes with metals. Here, we report a novel chitosan-based organometallic complex that was tested both as homogeneous and heterogeneous catalyst in the degradation of contaminants of emerging concern in water. The stoichiometry of the complex was experimentally verified with different metals, namely, Cu(II), Fe(III), Fe(II), Co(II), Pd(II), and Mn(II), and we identified the chitosan-Fe(III) complex as the most efficient catalyst. This complex effectively degraded phenol, triclosan, and 3-chlorophenol in the presence of hydrogen peroxide. A putative ferryl-mediated reaction mechanism is proposed based on experimental data, density functional theory calculations, and kinetic modeling. Finally, a film of the chitosan-Fe(III) complex was synthesized and proven a promising supported heterogeneous catalyst for water purification

Degradation of phenol with using of Fenton-like Processes from water

Phenol is one of the serious pollutants from the chemical and petrochemical industries. This pollutant due to its convoluted structure is resistant to biodegradation. One of the methods that are useful to remove this pollutant is advanced oxidation (AOP). A laboratory scale study was done on a synthetic wastewater containing phenol. All experiments were done in batch conditions and effect of variables pH, amount of hydrogen peroxide, iron dosage, contact time and an initial concentration on the phenol removal were tested. The remaining phenol concentration was evaluated using the DR-5000 device. In order to effect of these parameters, the experiment was performance at pH 2 to 6, 5 to 45 ml/ml of peroxide, and time of 5 to 60 minutes with 2 to 15 g/ml iron (Fe˚). The optimum pH, the ratio of hydrogen, Fe˚and time were 3, 15 ml, 8g and 5 minutes respectively. Chemical oxygen demand (COD) index was chosen as the parameter for evaluation in this study. Result showed that mineralization of phenol was not complete. The COD removal efficiency was obtained 71%. According to the results of this study, Fenton-like process can be used for conversion organic resistant compounds to other compounds with lower toxicity

The application of in situ generated hydrogen peroxide for corrosion inhibition, disinfection and pollutant degradation

This thesis describes the utilisation and activation of in situ generation of hydrogen peroxide (H2O2) from dioxygen (O2) for corrosion inhibition, disinfection and pollutant degradation. MnCl2· 4H2O and Tiron (disodium 4,5-dihydroxy-1,3-benzenedisulfonate) rapidly remove O2 from aqueous solution at a rate of ~20 mg∙ L^(-1) min^(-1) using hydroxylamine (NH2OH) as reducing substrate. A mechanism is proposed that involves two 1-electron transfers from bound NH2OH to bound O2 to produce H2O2 concomitant with two proton transfers from catecholate oxygen atoms. This system can act as an anti-corrosion formulation as the catalytic reduction of O2 results in the removal of O2 from open aqueous solutions and the in situ generated H2O2 can be used as a biocide e.g. to kill L. pneumophila. The same system, which involves manganese(II) ions (Mn(II)) and Tiron as the co-catalyst for the in situ generation of H2O2, was also utilised for the oxidative degradation of Calmagite (CAL, 2-hydroxy-1-(2-hydroxy-5methylphenylazo)-4-naphthalenesulfonic acid) at room temperature. Percarbonate (HCO4-) was found to be the main reactive species for CAL degradation in the added H2O2 system buffered by carbonate at pH 9.0 in the absence of Mn(II). Manganese(IV)=O (Mn(IV)=O) and manganese(V)=O (Mn(V)=O) are the main reactive species in the added H2O2/Mn(II) system buffered by carbonate and non-carbonate buffers respectively. This system was enhanced by activation using ultrasound and copper(II) ions (Cu2+) as catalyst, forming the Cu2+/O2/ultrasound/NH2OH (COUN) system for the degradation of bisphenol AF (BPAF). Using a two-stage kinetic model, quantitative analysis of the catalytic efficiency showed that Cu2+ was relatively stable in the COUN system in contrast to the Cu2+/H2O2/ultrasound (CHU) system. This work contributes to a better understanding of the use of Cu2+, NH2OH and O2 for the in situ generation of H2O2, as well as the role of Cu2+ and NH2OH in Fenton-like systems

Heterogeneous advanced photo- Fenton process using peroxymonosulfate and peroxydisulfate in presence of zero valent metallic iron: A comparative study with hydrogen peroxide photo-Fenton process

The present research work has demonstrated the use of zero valent metallic iron (Fe0) in the photo-Fenton process under the UV illumination as a promising and novel technique. Oxidants like oxone a peroxymonosulfate (PMS) and ammonium persulfate a peroxydisulfate (PDS) were used in comparison with classical hydrogen peroxide (HP). PMS was found to be a better oxidant in comparison with HP and PDS at higher pH conditions especially in the pH range of 5–7. PMS acts as better oxidant with dipolar unsymmetrical structure, higher oxidation potential and its lower LUMO energy can easily accept electrons more readily compared to the other two oxidants. The degradation rate for various oxidation processes at pH 3 shows the following decreasing order: Fe0/PMS/UV ≈ Fe0/HP/UV > Fe0/PDS/UV > HP/UV > PDS/UV> PMS/UV > Fe0/PMS/dark > Fe0/HP/dark > Fe0/PDS/dark > Fe0/UV > Fe0/dark. At pH 5, PMS/UV and PDS/UV systems show similar efficiencies as Fe0/PMS/UV and Fe0/PDS/UV process, since most of the Fe0 surface is covered by the precipitates of hydroxide and oxyhydroxides. Though recycling capability of iron powder is almost comparable for first to fifth repetitions, Fe0 retains its recycling capability better in the presence of HP for the further runs rather than PDS and PMS

Nanotechnology Solutions for Global Water Challenges

The lack of clean and safe drinking water is responsible for more deaths than war, terrorism and weapons of mass destruction combined. This suggests contaminated water poses a significant threat to human health and welfare. In addition, standard water disinfection approaches such as sedimentation, filtration, and chemical or biological degradation are not fully capable of destroying emerging contaminants (e.g. pesticides, pharmaceutical waste products) or certain types of bacteria (e.g. Cryptosporidium parvum). Nanomaterials and nanotechnology based devices can potentially be employed to solve the challenges posed by various contaminants and microorganisms. Nanomaterials of different shapes, namely nanoparticles, nanotubes, nanowires and fibers have the ability to function as adsorbents and catalysts. These possess an expansive array of physicochemical characteristics deeming them highly attractive for the production of reactive media for water membrane filtration, a vital step in the production of potable water. As a result of their exceptional adsorptive capacity for water contaminants, graphene based nanomaterials have emerged as an area of significant importance in the area of membrane filtration and water treatment. In addition, Advanced Oxidation Processes (AOPs) together with or without sources of light irradiation or ultrasound, have been found to be promising alternatives for water treatment at near ambient temperature and pressure. Furthermore, the uses of visible light active titanium dioxide photocatalysts and photo-Fenton processes have shown significant potential for water purification. A wide variety of nanomaterial based sensors, for the monitoring of water quality, have also been reviewed in detail. In conclusion, the rapid and continued growth in the area of nanomaterial based devices offers significant hope for addressing future water quality challenges