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This work used a time-integrated performance index to address the low cost of the Electrocoagulation process to strengthen its tetracycline removal performance significantly. A reasonable control of the time-depending tetracycline removal efficiency of the electrocoagulation process was searched by choosing a better combination of the electrode material and electrolyte species types for getting a stabilization condition of the total electric voltage. The response surface methodology was included to address, compare and rescue the best results of the time-integrated performance index. The electrolyte type, pH of the aqueous media, electric conductivity, and electric voltage were assessed to better respond to the performance of tetracycline removal. In this regard, an iron-based electrocoagulation reactor was operated over a range of 40 to 67 A m-2 of electric current density supported by 5 to 10 mS cm-1 electric conductivity values. To increase the electrical conductivity, four electrolytes (Cr3+, Zn2+, Ca2+, and K+) were added separately to tetracycline synthetic solutions. The best performance was obtained by Ca2+ electrolytes stabilizing the total electric voltage due to maintaining a constant electric conductivity and pH buffering at the alkaline region. From a Box-Behnken experimental design, a 40 A m-2 electric current density allowed getting the maximal time-integrated performance index value over 30 min time, removing above 97% tetracycline with minimal electric power consumption.

In recent years, several environmental pollutants have been monitored in surface waters and sediments. However, few studies apply multivariate statistics to identify the main components and correlate them temporally and spatially. In this sense, the present study sought to monitor the quality of water and sediments in the Rio Marrecas/Brazil, through the analysis of physicochemical parameters and trace elements, as well as to identifying sources of contamination, using multivariate statistics. For this purpose, sampling was carried out in nine locations for a period of 12 months. The Total Reflection X-ray Fluorescence (TXRF) technique was used to quantify the 15 elements identified in water and sediment samples. Through multivariate statistical analyses, the most significant elements, their correlations and possible pollutant sources were defined, and the pollution index (HPI) and assessment index (HEI) of heavy metals were applied. The parameters pH and BOD

In this work, the substitution of environmentally harmful additives in the industrial dyeing process of polyamide-6 microfiber-made knitted fabrics (PA-6µFKF) was studied. Using the disperse red 60 (DR60) dye, kinetic adsorption tests on the PA-6µFKF dyeing were performed by using either β-cyclodextrin (β-CD) additive, commercial leveling agents, or without additives. Equilibrium tests were also performed during 25 h. A modelling based on a dye adsorption process controlled by an intraparticle diffusion was proposed to represent the sets of kinetic data. Three isotherm models were also tested for representing the equilibrium data. The kinetic data have evidenced three main dye diffusion zones. Different adsorption mechanisms on PA-6µFKF surface dyeing was evidenced, being the data well represented by the two-step Langmuir isotherm. Finally, the best quality on color uniformity was attained using the β-CD additive, revealing a good alternative for the substitution of environmentally harmful additives in industrial dyeing processes.

Optimum experimental conditions for the photo-electro-Fenton (PEF) process using a lab-scale photo-reactor to treat a sanitary landfill leachate (SLL) were determined. The PEF process operational conditions were analyzed with a response surface methodology (RSM) that presented a high total carbon (TC) removal at the central point: current intensity of 2.3 A, H2O2 concentration of 9000 mg·L−1, Fe2+ concentration of 60 mg·L−1, an electrolysis time of 45 min and solution pH controlled at the range 3.5–4.5, reaching a minimum TC residual concentration of 344 mg·L−1 in the SLL, as well as 89 mg Pt-Co·L−1 of color, 254 nm = 0.18 a.u., 315 mg·L−1 5th day biochemical oxygen demand (BOD5), 782 mg·L−1 chemical oxygen demand (COD), improving the BOD5/COD = 0.4 ratio. The reaction byproducts were analyzed with gas chromatography-mass spectrometry (GC–MS). The generated byproducts were less toxic than the parent compounds found in the raw SLL. As the SLL toxicity was reduced, integration treatment strategies containing PEF processes and biological oxidation (BO) were studied. The best treatment strategy enabled the lethal concentration LC50% = 33% and reduced the residual TC concentration to 181 mg·L−1 through application of the PEF process. This possibly transformed recalcitrant compounds from raw SLL into more biodegradable substances (BOD5/COD = 0.53) facilitating the microbial activity in the posterior BO. This treatment strategy also produced a smaller number of identified byproducts, which confirms the good performance of the PEF process followed by BO.

This work aimed to use raw soybean hulls (RSH) as an adsorbent on the removal of BF-4B reactive red dye. Kinetic and equilibrium experiments were performed using the best conditions obtained from preliminary tests. Kinetic data were better represented by the pseudo-second order model, evidencing three well-differentiated mass transfer regions. By a statistical analysis of the fit of 7 equilibrium models and 2 model combinations to experimental data, it was observed that the adsorption occurred in a single molecule monolayer for final dye concentrations lower than ~63 mg L−1. After this concentration, a possible multimolecular monolayer was verified, evidencing the formation of aggregates or micelles, since the Langmuir-BET model was the best fit. The maximum adsorption capacity estimated was about 19 mg g−1. The results have proved that the soybean hulls could be used as an alternative adsorbent in the treatment of textile effluents, without the need for a pretreatment.

This paper presents a strategy for isolation, identification and evaluation of microalgae strains synthesizing biologically active compounds (BAC) with antimicrobial activity against food-borne and other pathogens. Water samples containing microalgae were initially submitted to the enrichment process, followed by standard procedure for obtaining pure culture. Purified DNA from the microalgae isolates was used for sequencing the amplified 18S rDNA genomic region, which resulted in the identification of Poterioochromonas malhamensis, Chlorella sp., Micractinium sp., Tetradesmus sp. and Desmodesmus sp. All isolated strains were cultivated in 1-L flat-plate PBRs, with the Poterioochromonas malhamensis being the only one to show antibacterial activity in agar diffusion assay. Further, PPEQ-01strain was cultured under different types and scales of PBR, intensity and spectrum of the incident light, in order to study and prove the antibacterial potential of the strain. Ethanolic and methanolic supernatants, or hydrophilic and methanolic extracts produced from biomass cultivated in different conditions led to formation of bacterial growth inhibition halos around the impregnated disks used in the agar diffusion test. The hydrophilic extract, obtained from biomass cultured under green illumination, exhibited stronger activity against all tested pathogenic bacteria as compared to the other extracts. The results obtained with the new isolated Poterioochromonas malhamensis strain proved efficiency of the innovative complex approach applied to BAC aiming the identification of microalgae that present antimicrobial activity.

In this work, the pollutant reduction performance in landfill leachate by combining both photo-Fenton and biological processes was investigated. First, conventional biological treatment was performed, consisting of a decantation process, with centrifugation at 5000 rpm for 15 min, followed by the biological process conducted at 2.36 ± 0.1 mg mg−1 (BOD5/MLSS) and 0.571 ± 0.04 vvm (L L−1 min−1) for 40 h. At the same time, in the application of the photo-Fenton process, a central composite rotatable design (CCRD) was applied to evaluate the effect of main process variables. The quadratic models of chemical oxygen demand (COD) and 5 days biological oxygen demand (BOD5) removal were proposed and validated, being separately used as objective functions during the search for optimal operating conditions. After the application of the conventional biological process, removals of 87 ± 2% and 84 ± 2% were obtained for COD and BOD5, respectively. For the photo-Fenton process under optimum conditions (3400 mg H2O2 L−1, 80 mg Fe2+ L−1, pH = 2.40 and 120 min), removals of 89 ± 3% COD and 75 ± 1% BOD5 were obtained. However, both processes did not meet effluent discharge standards. So, the optimized photo-Fenton process was then combined with the biological process, performed for 150 h with 1.571 ± 0.06 vvm and 4.41 ± 0.3 mg mg−1 (BOD5/MLSS). With the combined process, it was possible to treat an effluent with high organic load, achieving a removal of 98% COD and BOD5 and meeting the restrictive standards of release in recipient water bodies.

Glyphosate removal from contaminated water using a new adsorbent material was investigated. Graphene-MnFe2O4 nanocomposite supported on vegetal activated carbon (GO-MnFe2O4/VAC) was synthesized. Several characterization techniques such as transmission and scanning electron microscopy, N2 physisorption, energy dispersive X-ray spectrometry, Fourier transformed infrared spectroscopy, X-ray diffraction and Raman spectroscopy were used to have insights to this material. Furthermore, the point of zero charge was determined. GO-MnFe2O4/VAC material was evaluated for glyphosate adsorptive removal in fixed-bed column under different operating conditions of solution concentration and feed flow rate. The results pointed out that glyphosate adsorption using GO-MnFe2O4/VAC was favored at pH values between 2.29 and 6.14. In fixed-bed column, the best results were obtained for the solutions having higher concentrations and also for higher feed flow rates. The equilibrium experimental data were fairly described by Langmuir model with maximum adsorption capacity reaching 6.778 mg g−1. Among the mathematical models evaluated to describe the breakthrough curves, the best fit to the experimental data was obtained by model that considers the intraparticle diffusion and the internal diffusion step was considered to be the mass transfer limiting step. The present results indicated that the adsorbent material synthesized has a great capacity for adsorption and prove the potential of use of GO- MnFe2O4/VAC for glyphosate removal from contaminated water in the continuous mode of operation.

A biosorbent material based on tilapia scales for the removal of Cu(II) ions was investigated. Modifications in the biosorbent caused by retention of Cu(II) and by the pH effect were evaluated sepa...

In this work, a physical-chemical, elemental and microbiological groundwater monitoring was performed on wells of the Serra Geral aquifer, located in the western region of the Brazilian state of Paraná, along with an evaluation of the elemental composition of soil sediments in the region of groundwater monitoring. The monitoring was carried out in 10 wells distributed throughout the rural area of the municipality of Toledo-PR. Elemental analyses were performed using the analytical technique of total reflection X-ray fluorescence spectrometry. From the results obtained, it was observed that in some wells, iron and lead concentrations were above the maximum limits allowed by the Brazilian legislation in some months, demonstrating that the evaluated groundwater is susceptible to contamination. By the analysis of the soil sediments, the presence of iron and lead in the region soil/rock was verified, which may be associated to rainwater percolation making it necessary to periodically monitor the groundwater consumed by the population of the municipality of Toledo-PR.

In this research, the performance of a Fenton batch reactor (FBR) for the treatment of tannery effluent (TE) has been studied by applying response surface methodology (RSM). In the context of RSM, three important Fenton parameters (Fe and H2O2 concentrations and solution pH) were suitably changed within a full experimental design, allowing the definition of a set of 27 FBR experiments performed in batch mode. From the RSM analysis, the Fenton oxidation process showed the best removal response for chemical oxygen demand (COD) (80%), color (90%), turbidity (95%), and sludge (70%), as well as an increase in the percentage of biodegradation from 0.19 to 0.3 (BOD5/COD ratio) when conducted under conditions of 5 mg Fe2+ L−1, 75 mg H2O2 L−1, and pH 4 with a 60 min reaction time. Additionally, quick consumption of the initial concentration of H2O2, as observed in an acidic solution pH (∼3.5) containing dissolved iron, led to rapid yield of hydroxyl radicals (HO•), making it possible to oxidize the organic pollutants in the raw TE more efficiently. By performing kinetic experiments on the best pollutant removal, it was observed that there were high reductions in the amounts of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and total dissolved carbon (TDC). Conversely, an increase in the initial concentration of total dissolved nitrogen (TDN) was also observed, suggesting a partial mineralization of nitrogen compounds such as ammonia, nitrate, and nitrite. The Fenton reaction coupled to the Zahn-Wellens test indicated and increase in the biodegradability (Dt 79%) of the treated TE. Gas Chromatography – Mass Spectrometry (GC–MS) analysis identified contaminants present in the raw TE and persistent in the samples treated by the Fenton reaction coupled to the Zahn-Wellens test. Based on the overall results, the Fenton process has been shown to be a simple and suitable way to treat TE efficiently. The process could also be used as a pre-treatment of a conventional biological system, being applied in the degradation of toxic and recalcitrant contaminants contained in TE.

In this work, the degradation and mineralization of Ciprofloxacin molecules by an UV-C/H2O2 process has been investigated, aiming to improve its performance based on a response surface methodology. In the context of the UV-C/H2O2 process, the influence of the initial H2O2 concentration and solution pH on Ciprofloxacin degradation performance was investigated for long duration UV irradiation times, up to 600 min. The main by-products yielded from the process were monitored by gas chromatography–mass spectrometry, and the genotoxicity of the effluent was assessed using the bioindicator Allium cepa. The best results for Ciprofloxacin removal were obtained when the reactor was operated at an initial H2O2 concentration of 200 mg L−1 and solution pH of 3.2. Gas chromatography–mass spectrometry analysis allowed to identify the formation of a series of intermediary by-products, such as phenolic antioxidants and phthalates. From the genotoxicity and antibacterial effects tests, an increase in the mitotic index and a decrease in the inhibition halos of the treated Ciprofloxacin samples for 420 and 600 min irradiation times was observed, suggesting a reduction of the toxic and cytotoxic potential of the main by-products yielded. The UV-C/H2O2 process-based Ciprofloxacin treatment exhibited an excellent performance and is suggested as an interesting alternative for the reduction of the toxic, carcinogenic, and mutagenic effects caused by the inappropriate disposal of emerging contaminants in water bodies.

In this work, the potential of peach pit biosorption in the removal of the drug metformin hydrochloride from water is evaluated. Experiments are carried out in a closed batch system to evaluate the effect of the solution pH (2–10), temperature (25, 35 and 45 °C), stirring (100, 150 and 200 rpm) and chemical treatments. During the study, biosorbent characterization, kinetic tests, equilibrium tests and thermodynamic parameter calculations are performed. The operating conditions that show the best results for both the raw biosorbent and the biosorbent submitted to acid, basic and acid followed by basic treatments with removal capacities of 3.17, 10.83, 18.10 and 49.14 mg g−1, respectively, are pH 7, 25 °C and 100 rpm, which result in an equilibrium time of 12 h. In the kinetic study, the pseudo-second-order model represents the best fit for the experimental data, while the Langmuir model best represents the equilibrium data. The biomasses submitted to chemical treatments show a significant increase in drug removal capacity related to the raw biosorbent, with the best maximum absorption of 82.54±1.34 mg g−1 achieved after the application of the acid followed by basic treatment. These results show that peach pit has potential to be used as a low-cost biosorbent to remove drugs from water.

This work aimed to perform selective experimental arrays based on the electro-Fenton hybrid (EFH) process for pollutants abatement and toxicity reduction in brewery wastewater (BW). Fenton and electrocoagulation (EC) methods were assessed preliminarily, including the Fe2+ catalyst yield and H2O2 loss. Each method performance on reducing total organic carbon (TOC) was assessed using a 33 full factorial design (FFD). Firstly, Fe2+ species were produced in short time ranges with the electric current density at 50 A m−2 and electrical conductivity at 1200 μS cm−1, followed by EFH experiments with an initial addition of 9.0 g L−1 H2O2. In three levels, initial pH (2.5–3.5) values, Fe2+ production-dedicated time (5–15 min), and H2O2 renovating percentage (70–90%) were also evaluated, assessing TOC removal. Secondly, nine EFH kinetics, upon the addition of an initial 9.0 g L−1 H2O2 along with H2O2 addition at 82.5%, every 5 min, and three levels for pH (3.0–3.4) were carried out, beginning after three Fe2+ production-dedicated times (4–6 min). Thirdly, another 60 min kinetic experiment was proposed, with an initial 6 min EC process, followed by a 39 min EFH process, and finally, a 15 min EC process, assessing TOC removal and remaining toxicity. A significant improvement in TOC removal performance, about 90%, along with high toxicity reduction was attained after a refined EFH-based treatment. Therefore, keeping permanent EFH conditions with more suitable parameters provided a unique perspective for removing highly significant pollutants.

In this study, strong evidence of anthropic pollution was identified in the waters of the Boi Pigua River near the municipal landfill of Cascavel-PR. The elemental composition of the river water from five collection sites, the groundwater from four sites and the municipal landfill leachate were monitored over 1 year, using the total reflection X-ray fluorescence (TXRF) technique. Ten elements (Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, and Ba) were identified in the water samples. The elemental concentration data set was reduced to specific variabilities and characteristic clusters by applying cluster and principal component analysis (PCA). The greatest variability in concentration was observed in the Mn and Ba data, which formed the first, main component. A further three principal components were needed to explain the variability in the Ni, Cu, and Fe concentrations. According to the cluster analysis, samples from all the river and water table collection sites shared similarities with the landfill leachate composition. Thus, it is possible to affirm that the quality of the Boi Pigua River water has undergone major changes and an immediate intervention of environmental agencies is required.

The objective of this study was to evaluate the biosorption dynamics of heavy metals by the dead macrophyte Egeria densa in fixed bed column. Experiments were conducted with mono- and bi-component solutions of Cd(II) and Zn(II) at pH 4.0, temperature of 30 °C and volumetric flow rate range between 2 and 6 cm3 min−1. A mass transfer mathematical model was applied for describing the mono-component biosorption dynamics. In this model, the equilibrium was represented by the batch Langmuir isotherm, and intraparticle diffusion was considered as the rate-limiting step for the mass transfer. The mass transfer coefficient (KS) was estimated by the downhill simplex optimization method for each volumetric flow tested, while the axial dispersion coefficient was calculated by empirical correlations. The KS coefficients and the equilibrium parameters obtained in a mono-component batch system were validated using data from the breakthrough curves of the Cd(II) and Zn(II) binary mixture obtained for different volumetric flows and initial concentrations of each metal ion.

In this work, the analytical capability of the total reflection X-ray fluorescence technique with the S2 PICOFOX spectrometer was investigated. A set of certified reference materials was prepared as solid particulate for TXRF analysis. Experimental data of sensitivity, limits of detection and recovery for many elements were obtained. Good sensitivity and limits of detection with a good recovery range of around 90–110% were achieved. Thus, the TXRF technique exhibits a good analytical potential for its applicability on different materials.

In this paper, the removal capacity of grape pomace was evaluated removing the KROM Brown KGT dye. Initially, batch adsorption tests were conducted to evaluate the operating parameters, which indicated 2.0 as initial pH, particle size between 0.14–1.4 mm and temperature of 25 °C, for initial dye concentration of 100 mg L−1. Based on these operating conditions, kinetic and adsorption equilibrium data were obtained. The resulting equilibrium time was 12 h. The kinetic model of pseudo first order was the one that best represented the experimental data. The adsorption equilibrium data suggest a process of monolayers, according to the Langmuir model, with a maximum biosorption capacity of 180.2 ± 3.2 mg g−1. The thermodynamic data suggest a thermodynamically favorable and exothermic process. Based on the results, it was found that the grape pomace has potential to be used as biosorbent in wastewater treatment systems containing dyes.

The aim of this work was to determine the optimal Photoperoxi-Electrocoagulation (PPEC) process experimental conditions for the treatment of a tannery industrial wastewater (TIW). The lab-scale PPEC-reactor comprises a pair of iron-flat plates, resulting in a contact effective area of 58.5 cm2; the PPEC reaction was conducted by electrochemical phenomenon associated to a Fenton’s reaction based on the H2O2 concentrations added, the solar UV–vis light was exposed, as well as iron ion dissolved original plate deterioration, resulting in a production of an efficient hydroxyl radical ( OH). An optimising analysis using a response surface methodology was performed; the optimum conditions of the PPEC process were attained at a solution pH of 4, current density of 34.2 mA cm−2, 6 g H2O2 L−1 and an electrolysis time of 120 min. The effects on the removal of chromium and COD were evaluated, suggesting satisfactory results for the PPEC reaction. Based on the low calculated median lethal dose (LD50) values from a lettuce-seed-based ecotoxicity test, untreated TIW samples were completely lethal for doses with 100%, except for samples taken after 90 and 120 min. The PPEC process could be applied as an efficient low-cost alternative treatment for the removal of pollutants from TIW with a low environmental impact.

Leakage of transformer dielectric fluids is a concern because it may pose a risk of environmental contamination. In this study, the deleterious effects of vegetable and mineral dielectric fluids in water bodies were investigated using biodegradability and acute toxicity tests with Danio rerio and Artemia salina. Regarding biodegradability, all four tested vegetable oils (soy, canola, sunflower and crambe) were considered as easily biodegradable, presenting degradation rates significantly higher than the Lubrax-type mineral fluid. Acute toxicity tests were performed in two separate experiments without solution renewal. In the first experiment, the organisms were exposed in direct contact to different concentrations of vegetable (soy) and mineral (Lubrax) oils. Total soy-type vegetable oil has a higher toxic effect than Lubrax-type mineral oil. In the second experiment, the organisms were exposed to increasing percentages of the water-soluble fraction (WSF) of both types of tested oils. The LC50 values for the water-soluble fraction of the Lubrax-type mineral oil were about 5 and 8% for the Danio rerio and Artemia salina bioindicators, respectively, whereas the vegetable oil did not present toxic effect, regardless of its WSF. These results have shown that a strict selection of dielectric fluids and monitoring the leakage from power transformers is a serious duty of environmental protection agencies.

The performance of the electrochemical peroxidation (EP) process on the degradation of ciprofloxacin (CIP) was investigated. Different EP process conditions were assessed using an electrolytic cell based on stainless steel electrodes and O2 injection. Parameters, such as H2O2 (25–1000 mg L−1), electrical current density (ECD) (19.71–164.26 A m−2), Fe2+ (0.5 and 2.0 mg L−1), initial solution pH (2.5–9.0), and electrolysis treatments (5–90 min), were varied to determine the best EP performance. Changes in CIP, total organic carbon, and residual H2O2, as well as solution pH, were monitored during the EP performance analysis. Additionally, a set of intermediary by-products and chemical element concentrations was identified and quantified. The toxicity levels of the samples, in terms of the median lethal concentration (LC50), were assessed with Lactuca sativa-based bioassays tests. By setting the ECD, initial H2O2 concentration, initial pH, and electrolysis treatment to 32.85 A m−2, 100 mg L−1, 3, and 30 min, respectively, the optimal EP performance on CIP removal was attained. Conversely, low toxicity levels were observed for shorter electrolytic treatments (

We present a feasibility study of different adsorbent materials, namely residual fish scales biosorbent (FS), mineral dolomite (DL) and commercial resin (CR) in the heavy metals removal in multicomponent solution based on the properties of a real effluent from automotive battery recycling industry. Considering the effluent complex characteristics, the materials were assessed aiming to provide not only the heavy metals removal, but also the effluent neutralization and lower sludge generation. For this, all the studied materials were physicochemically and morphologically characterized with the aim of understanding the mechanisms involved in the process. Further, the elemental compositions of the solid and liquid phases generated from each treatment process were assessed by X-ray fluorescence spectrometry. The effluent presented highly acidic characteristics and heavy metals above the legislated limits for discharge (Fe, Zn and Pb). Each adsorbent material followed different mechanisms which led to dissimilar removal and neutralization capacities. The CR showed remarkable heavy metals removal capacity governed by an ion exchange mechanism; conversely, it did not show a neutralization effect. In contrast, FS and DL presented lower removal capacities by complex simultaneous phenomena (ion exchange, precipitation and/or complexation), but a great neutralization potential related to leaching of alkaline constituents. When sludge generation is considered as a key factor, mitigation and enhancement of treated effluent quality could alternatively be addressed by employing the materials in hybrid processes. Hence, the associated use of such materials could be viable yet very challenging for both neutralization and removal of heavy metals from the battery effluent.

The improvement of pollutant removal, in addition to low toxicity and a high biodegradability index, from sanitary landfill leachate (SLL) effluents treated in a two-process purification system was investigated. As a purification strategy, an electrocoagulation (EC) process followed by a biological purification step was applied. The response surface methodology was used to study the best EC process performance as a function of initial pH, current density and electrolysis time. The maximum removal of turbidity, chemical oxygen demand (COD) and iron concentration were achieved at an initial pH of 5, a current density of 128.57 A m −2 and an electrolysis time of 120 min. Regarding the best EC conditions, toxicity, based on an Artemia salina bioassay, and biodegradability, based on the Zahn-Wellens test, were assessed in raw SLL effluents and after their treatment with EC and biological processes. After stripping almost 98% ammonia of the concentration after EC experiments at 0, 5 and 120 min electrolysis times, the toxicity was also assessed. From the bioassay tests, the best result for the toxicity level was achieved for a 5 min electrolysis time. The Zahn-Wellens test showed that the EC process as a first stage of a two-phase treatment system was sufficient and provided a biodegradability index above 70%. By treating with a biological process, a significant improvement in toxicity was attained. However, most probably, the remaining toxicity could be attributed to ammonia. Thus, a pre-treatment based on the EC process integrated to a biological one can be considered as a promising and challenging alternative.

In this work, new insights on organic matter (OM) removal performance along with the assessment of the toxicity of landfill leachate (LL) treated by Electrocoagulation (EC) method were investigated. In the context of response surface methodology (RSM), the optimal EC experimental conditions were sought by applying a 33 complete factorial design, regarding pH, current density and electrolysis time as operational parameters. The sum of dissolved organic and inorganic carbon, namely as dissolved total carbon (DTC), was chosen as a global response parameter. Other EC experiments were performed, keeping fixed pH and current density at local optimal values and varying the electrolysis time. Determination of the median lethal concentration (LC50) from bioassays based on Artemia salina and Lactuca sativa indicators was performed. A second-order polynomial function was statistically validated with good predictions of the DTC data, indicating best removals by setting values of pH, current density, and electrolysis time at 5, 128.57 Am−2 and 120 min, respectively. Additionally, removals above 90% were achieved for color, turbidity, iron concentration and dissolved inorganic carbon, whereas reductions on related-to-organic matter parameter values were around 60%. Although the EC treatment reduced the LL effluent toxicity, as verified by toxicity bioassays, 90 min treatment times showed best results on LC50, but higher toxicity was persistent in electrolysis times below 40 min. Thus, a second stage of treatment based on a biological process could be suitably included in order to abate recalcitrant OM and decrease remaining toxicity in a more efficient integrated treatment system.

The aim of this work was to evaluate the effect of the acidic surface oxygenated groups and textural properties onto the adsorbent surface towards dibenzothiophene removal. The samples were prepared from an activated carbon derived from coconut shell (AC), by oxidative (ACO) and thermal (ACT) treatments. Morphological and chemical analyses were performed to characterize the adsorbents. The adsorption experiments were carried out in batch and closed system. The Langmuir isotherm model was used to describe equilibrium data, while kinetic data were described by the Homogeneous Surface Diffusion Model. The characterization results indicated that the adsorbents are predominantly microporous materials with effective surface area higher than 750 m2 g−1 (AC = 753 m2 g−1, ACT = 802 m2 g−1, ACO = 755 m2 g−1). It was observed a decrease in the amount of oxygenated functional groups in the ACT (310 µmol g−1) in relation to AC (738 µmol g−1), while for the ACO this amount was increased (2630 µmol g−1). The insertion of oxygenated functional groups on the adsorbent’s surface promoted an increment of density of sites (AC = 0.98 µmol m−2, ACT = 0.38 µmol m−2, ACO = 3.48 µmol m−2) what, consequently, led to the enhancement of the adsorption capacity. Also, the oxidative treatment provided a more favorable mass transfer kinetics with an increase of 89% enhancement for the diffusivity coefficient. These results indicate that an increase of effective specific surface area and acidic oxygenated groups can improve the adsorption performance of the carbon-based adsorbents for desulfurization purposes.

The current study applied Fe(III)-carboxylates, like Ethylenediamine tetraacetic acid (EDTA), oxalic acid and citric acid, in photo-Fenton reactions in the treatment of sanitary landfill leachate using simulated solar irradiation. The complex formation is justified by drawbacks identified in conventional Fenton and photo-Fenton reactions, such as the acidification step that precedes a decrease of the organic load before the initiation of the oxidation. By employing a lab-scale photo-reactor to treat osmosis concentrate landfill leachates, the main operational parameters, like solution pH, iron and chelating agent concentration, H2O2 consumption and required energy were evaluated as a function of decoloration and decrease of 254 nm absorbance in the sanitary landfill leachate. The best results were found with the photo-reactor operating at pH 6.0, 100 mg Fe(III):EDTA L−1; consuming 275 mM H2O2 and demanding about 8 kJUV L−1, providing the total decoloration and 80% reduction of the 254 nm absorbance in landfill leachates. Under such conditions the decrease of the organic load was satisfactory, including the reduction of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), 5th day biochemical oxygen demand (BOD5) and chemical oxygen demand (COD), and probably improving the treatment conditions in terms of biodegradability of the sanitary landfill leachate (BOD5/COD ratio).

The aim of this work was an experimental and theoretical investigation of the influence of electrolyte (NaCl) and surfactant (SP), as textile auxiliary agents (TAAs), onto reactive blue 5G (RB5G) dye removal by applying untreated fish scales (FS) in batch system. Kinetic and equilibrium studies were performed, aiming at the comprehension of the mass transfer mechanisms through phenomenological modeling. The biosorbent was texturally characterized, to investigate the adsorbent's characteristics and to support the models' assumptions. Hence, a 'physically meaningful' modeling to assess different systems containing dye-TAA mixtures was employed. The experimental results indicated that despite the FS nonporous characteristics, it showed remarkable adsorption capacities (≈291 mg g-1), which may be ascribed to the adsorbent-adsorbate affinity and to dye-aggregates adsorption onto the FS surface. Those results evidence a potential use of FS as an alternative biosorbent material. The mathematical model was able to identify the rate-limiting step of the process; to predict the adsorption kinetics and equilibrium condition, comprising the description of aggregates formation; and to successfully predict kinetic behavior of independent data in simulated real effluent. Those results indicate that the model can be used to simulate operating conditions and, therefore, support the design, optimization, and scale-up of adsorption processes.

This work focused in the assessment of the potential of reactive blue dye 5G (RB5G) adsorption by polymeric adsorbent Dowex Optipore SD-2 (DOSD-2) in closed batch system by a phenomenological investigation of the adsorption process by both experimental data and mathematical modeling of kinetics, equilibrium and thermodynamics. The kinetic model of adsorption on the adsorbent sites described experimental data, consequently the adsorption itself is the rate-limiting step of the overall process, instead of diffusional steps. This kinetic model reduces to Langmuir isotherm in equilibrium condition, which in turn adequately described the solid-liquid interface equilibrium. Both kinetic, namely, adsorption kinetic constant ( k a ), and isotherm parameters: maximum adsorption capacity ( q max ) and adsorbent-adsorbate affinity ( b ) provided data to the thermodynamics investigation, which was evaluated by means of: (i) activation energy ( E a ) calculated Arrhenius equation; and (ii) enthalpy of adsorption ( Δ H ) determined by the Henry constant with the estimated parameters. In this sense, the proposed model presents a theoretical investigation of the entire process by an interdependent approach. Results showed higher adsorption capacity in acidic pH values (i.e. pH = 2 – lower than adsorbent’s zero point charge: 4 zpc Δ H and E a suggested to a physical nature and endothermic sorption process. Morphological and chemical characteristics of the adsorbent-adsorbate system indicated the possibility of aggregates formation and hence sterical limitations for the dye in the DOSD-2 adsorbent pores, on spite of that high adsorption yield of RB5G dye presented by DOSD-2 (≈700 mg g −1 ) was achieved demonstrating its great potential for textile effluents containing reactive dyes.