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In this study, the removal of five imidazolium-based ionic liquids (ILs) from water was accomplished by a heterogeneous electro-Fenton treatment. Different ILs were selected in order to study the effect of the alkyl chain length and the nature of the anion. Initially, the effect of the catalyst (iron alginate beads) dosage and current were evaluated. The results showed that the optimum conditions were attained when operating with 4.27 g of catalyst and 0.3 A, achieving degradation yields and TOC reductions higher than 95% after 90 min and 80% after 480 min, respectively. Regarding the ILs with common cations, lower degradation rates were obtained for those with longer alkyl chains, thus 1-ethyl-3-methylimidazolium dicyanamide, exhibits faster degradation than 1-hexyl-3-methylimidazolium dicyanamide and 1-butyl-3-methylimidazolium dicyanamide. In addition, the influence of the counter anions on the oxidation rate of different ILs under an electro-Fenton treatment was demonstrated, following the order: methylsulfate > dicyanamide > acetate. The Microtox ecotoxicity tests of the initial and treated samples revealed that none of the three studied ILs with shorter alkyl chain lengths showed toxicity and only 1-hexyl-3-methylimidazolium dicyanamide and 1-butyl-3-methylimidazolium dicyanamide presented toxic levels, with EC50 values of 269.85 and 47.55 mg L−1, respectively. Nonetheless, after 480 min of heterogeneous electro-Fenton treatment at 0.3 A, the toxicity of both was completely reduced. Finally, to confirm the mineralization of these compounds, the identification of several reaction intermediates in the heterogeneous electro-Fenton treatment of three ILs was assayed and a plausible degradation pathway was proposed.

The present study focuses on the electrokinetic process for the in situ formation of electroactive species at the anode. A bench scale experiment was conducted to investigate the organic molecule degradation by in situ electroactive species and simultaneous removal of trace metals in soil contaminated by a textile effluent. With an impressed direct current (DC), the voltage gradient of 2 V cm−1 facilitated the dye/metal ion movement in the contaminated soil towards the electrodes by electromigration. Two different electrolytes were evaluated for the degradation of pollutants in the soil. Thus, 0.5 M potassium sulfate was assayed as the anolyte and catholyte for system I and in system II, distilled water was used as the electrolyte. The EK process experiments were conducted for 120 h. The UV-Visible spectrum revealed the presence of humic substances in the anolyte chamber during the EK process. The EK treatment was accomplished by the in situ anodic generation of electroactive species. These species were able to degrade the organic components efficiently. The formation of peroxide was noticed in the range of 18 to 32 mg L−1 (system I) during the anodic EK processes. After the EK process, the total organic content was reduced by about 68% and 41% for system I and system II, respectively, which clearly indicates that the significant removal of organic content in system I as compared to that in system II. The trace metals nickel, chromium and copper were significantly removed from the contaminated soil. This technology may be exploited for a faster and eco-friendly degradation and removal of textile dye and inorganic substances in the soil environment.

The application of acid mine drainage sludge (AMDS), an industrial waste with high metal content, as catalyst for the electro-Fenton-like technology on the treatment of organic polluted effluents has been investigated. The study has demonstrated the potential use of this waste using dye Lissamine Green B as a model contaminant, which allowed the optimization of sludge dosage and pH. AMDS proved to perform a high decoloration rate at pH 2, however, acidic conditions favored metal leaching. Alginate gel beads were selected to immobilize AMDS and to avoid metal release and the wash out of the reactor operating in continuous mode. This developed catalyst showed high reliability and efficiency in successive batches. The efficacy of the established treatment was also verified on the degradation of pesticide pirimicarb and a degradation pathway was determined by LC-MS studies.

The degradation of m-cresol (MC) has been investigated by a heterogeneous electro-Fenton process using iron loaded activated carbon (Fe-AC) as the heterogeneous electro-Fenton catalyst. Experimental results demonstrated that MC was effectively removed through an electro-Fenton process. Calculated TOC removal and overall energy consumption showed that the use of a low iron concentration (28 mg L−1) increases the efficiency of the process. The reactions followed a pseudo-first order kinetic equation and kinetic coefficients confirm that the MC reduction, when it is alone, is faster than in the presence of a similar compound, tert-butylhydroquinone (TBHQ) (from 0.0935 to 0.0692 min−1); therefore TBHQ exerts an antioxidative protection effect. In all cases, it is concluded that heterogeneous electro-Fenton treatment with Fe-AC follows a two-step process: adsorption and oxidation; allowing removal rates higher than in the literature. In addition, the reusability of this catalyst was demonstrated by operating it in continuous mode. Finally, LC-MS analysis allowed the development of a plausible degradation route.

In the current situation, soil salinity has increased due to the uncontrolled discharge of industrial effluent. In the present investigation, an electrokinetic (EK) technique was used for the inclusion and removal of sulfate in farming soil. Initially, the influence of the electrode distance was evaluated by the use of two cell configurations. The nature of the catholyte was assessed for the inclusion of sulfate in the soil. Decolorized textile effluent and 5% Na2SO4 were tested as the catholyte and double-distilled water as the anolyte for the inclusion process. Subsequently, selection of the electrolyte concentration and pH was investigated for the removal of sulfate concentrations in contaminated farming soil. Optimization of the pH and electrolyte for the process of sulfate removal in farming soil was performed and a mechanism of the removal process was proposed. A total of 96% sulfate removal was achieved using 0.01 M hydrochloric acid at a pH of 4.5 for a 96 h EK experiment. The initial conductivity of the soil was 5.32 dS m−1, and after sulfate removal the conductivity was about 0.714 dS m−1 and the energy consumption was 119 kW h m−3 for the farming soil.

Nowadays, a wide variety of pollutants are discharged to different water sources and become water contaminants. To overcome this problem, bioremediation has been studied as an alternative for their treatment due to its low cost, high efficiency and environmentally friendliness. However, it is necessary to search for microorganisms able to remediate pollutants of different nature. In this work, the isolation and identification of remediating-bacteria from polluted marine coastal sediment were carried out. The isolation assays were carried out using phenanthrene as the only carbon source. The identification of the strains was performed by PCR amplification of 16S rDNA. It was resolved in one band and the sequencing showed that this band was derived from Serratia plymuthica. The removal ability of this microorganism was assayed with phenanthrene, benzo[a]pyrene, different insecticides and Cr(VI). The isolated bacterium showed high removal ability of imidacloprid, methomyl, fenamiphos, and Cr(VI). After that, bioreactor scale-up (5 L) was studied with a mixture of these pollutants. Total removal degrees were obtained for organic compounds and around 96% of Cr(VI) removal was reached. Furthermore, the removal rate of the different pollutants fitted well to a logistic model. The present study states that the identified bacterium can play a vital role in bioremediation of an aquatic environment polluted with mixtures of contaminants.