Synthetic Effluent Research Articles

Facile and scalable preparation of ZIF-67 decorated cotton fibers as recoverable and efficient adsorbents for removal of malachite green

Recently, metal–organic frameworks (MOFs) have received considerable attention as highly efficient adsorbents for dye wastewater remediation. However, the immobilization of MOFs on the substrate surfaces to fabricate easy recyclable adsorbents via a facile route is still a challenge. In this work, ZIF-67/cotton fibers as adsorbents for dye removal were prepared in a large-scale using a simple coordination replication method. The successful fabrication of the ZIF-67/cotton fibers was confirmed by FTIR, XRD, XPS, SEM and BET analysis, respectively. As expected, the as-prepared ZIF-67/cotton fibers exhibited high adsorption capacity of 3787 mg/g towards malachite green (MG). Meanwhile, the adsorption kinetics and isotherm obeyed the pseudo-second-order kinetics and Langmuir model, respectively. Moreover, its removal efficiency towards MG was not significantly influenced by the pH and ionic strength of aqueous solution. Most importantly, the ZIF-67/cotton fibers can remove MG from synthetic effluents, and it can be easily regenerated without filtration or centrifugation processes, with the regeneration efficiency remaining over 90% even after 10 cycles. Additionally, the ZIF-67/cotton fibers presented excellent antimicrobial performance against E. coli and S. aureus. Hence, the distinctive features of the as-prepared ZIF-67/cotton fibers make it promisingly applicable for the colored wastewater treatment.

Synergistic catalytic degradation of ciprofloxacin using magnetic carbon nanomaterial/NiFe2O4 promoted cold atmospheric pressure plasma jet: Influence of charcoal, multi walled carbon nanotubes and walnut shell

BackgroundCurrently, water polluted to antibiotics such as ciprofloxacin (CIP) has been a main concern for the ecosystem and environment. Hence, the removal of these emerging contaminants is essential. MethodIn this research, a hybrid process including magnetic carbon nanomaterial/NiFe2O4 promoted atmospheric non-thermal dielectric barrier discharge plasma jet (APJ) as an environmentally friendly hybrid system was evaluated for eliminating CIP from polluted synthetic effluent. Multi walled carbon nanotubes (MWCNTs), activated carbon formed using charcoal (ChAC), and the walnut shell was applied as the carbonous source. Besides, to solve the separation problem, the charcoal, as optimum sample, was magnetized with NiFe2O4 (ChAC/NiFe2O4) using the treatment solvothermal route. Characterizations of all carbon materials were carried out by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda and vibrating-sample magnetometer analyses. FindingThe degradation amount for 80 mg/L CIP gained 48.8, 80.8, and 98.1% over APJ system + walnut shell, MWCNTs, and ChAC, respectively, after 90 min at 15 kVp-p output voltage and 0.05 g/L of catalyst loading. The results showed the ChAC/NiFe2O4 (87.2%) had less removal than ChAC (98.1%), but it has magnetic properties that can facilitate the separation problem.

Enhanced aquaculture effluent polishing by once and repetitive nutrients deprived seawater Chlorella sp.

The nutrients-rich aquaculture effluent may cause severe environmental and ecological destructions if discharged without adequate treatment. Microalgae can serve as a good candidate in aquaculture effluent polishing since it can realize water purification as well as in situ resource transformation as aquaculture feeds comparing to traditional remediation efforts. Enhanced nutrients removal by nutrients deprived microalgae has been revealed before, but repetitive nutrients deprivation is so far applied only for biofuel production purposes, and it is still unclear whether such a strategy can be adopted for further effluent polishing. This study comprehensively investigated the improved aquaculture effluent polishing by once and repetitive nutrients deprivation of indigenous seawater Chlorella sp. Synthetic effluent of various strengths (total nitrogen = 2–50 mg/L, total phosphorus = 0.2–5 mg/L) were first treated by nutrients replete microalgae, then subsequently polished by nutrients deprived microalgae. A semi-continuous sequential system was established and evaluated at various dilution plans, using both nutrients replete and repetitive nutrients deprived microalgae. Results showed that nutrients replete microalgae could only polish low strength aquaculture effluent to discharge acceptable levels (dissolved inorganic nitrogen≤0.5 mg/L, phosphate≤0.05 mg/L), while a following treatment by nutrients deprived microalgae could also treat moderate strength effluent to meet the discharge limits, and the improved nutrients removal was most efficient (>90% removal) during the first two days of effluent polishing. The semi-continuous sequential system with repetitive nutrients deprivation at two-day intervals could polish the high strength effluent to discharge acceptable levels respectively after 5, 7, and 9 days, using 1, 2, and 3 days of water exchange intervals in each circulation treatment. The extra microalgal biomass produced during repetitive nutrients deprivation (0.28–0.8 g/L biomass increase during each round of deprivation) was advantageous for system scale-up, or could be utilized as in situ aquaculture feed or other value-added products due to its lipid and carbohydrate rich properties.

Photodegradation of powerful five estrogens collected from waste water treatment plant over visible-light-driven Au/TiO2 photocatalyst

In wastewater effluents, the removal of endocrine-disrupting chemicals (EDCs) through the traditional remediation approaches is insufficient, and the existence of EDCs may cause human health risks and potential ecological even at low concentrations. In this contribution, the kinetics and efficiencies of photodegradation for individual estrogens and multicomponent estrogens solution of diethylbestrol (DES), estrone (E1), 17 β - estradiol (E2), 17- α Ethinyestradiol, (EE2) and Estoril (E3) were performed over Au/TiO 2 photocatalyst through UV and visible light exposure. The photodegradation efficiency for single component estrogen of DES, E1, E2, E3 and EE2 over 0.1%Au/TiO 2 photocatalyst under UV illumination was determined to 99.5%, 100%, 100%, 97.2% and 100% within 30 min. The estrogens in the multicomponent mixture of E1, E2 and EE2 were removed, reaching about 97.78, 88.60 and 92.10%, respectively, within 40 min of UV illumination, and they were almost completed within 75 min under visible light illumination. The degradation rate constants (k) values for single component experiments of estrogens, follows the trend of EE2 (0.352 min −1 ) > E1 (0.235 min −1 ) > DES (0.115 min −1 ) > E2 (0.111 min −1 ) > E3 (0.069 min −1 ). In addition, k values under UV illumination for target estrogens in multicomponent follows the sequence DES (0.179 min −1 ) > E1(0.12 min −1 ) > E3 (0.061 min −1 ) > E2(00.054 min −1 ). However, under visible light illumination the k values are followed the orders E3 (0.097 min −1 ) > DES (0.08 min −1 ) > E1(0.07 min −1 ) > E2(0.066 min −1 ). The obtained k values of estrogens treated with 0.1%Au/TiO 2 photocatalyst in the present work through UV and visible light exposure was greater than that reported in the previously published work. Overall, 0.1%Au/TiO 2 photocatalyst demonstrated superior performance for photodegradation of DES, E1, E2, E2 and EE2 in synthetic solution and wastewater effluent collected from Kuwait’s Kubd Waste Water Treatment Plant The photodegradation mechanism of estrogens over Au/TiO 2 photocatalyst discussed depends on the basis of the attack of ⋅ OH. • Wastewater effluent was collected from Kuwait’s Kubd Waste Water Treatment Plant. • The photodegradation of multicomponent estrogens were performed under illumination. • 0.1%Au/TiO 2 photocatalyst was utilized as efficient photocatalyst under illumination. • The degradation efficiency for single estrogen was achieved (100%) within 30 min. • Rate constants (0.352 min −1 ) of estrogens was greater than the previously reported.

Micellar enhanced flocculation for the effective removal of reactive yellow 160 from synthetic textile effluent

This work provides insight into the surfactant-based removal of reactive yellow 160 (RY-160) present in the aqueous medium. Micellar enhanced flocculation technique was applied and optimized for the said purpose. The mixture of anionic surfactants, obtained from a bio-degradable source (base soap), has been found to have great potential to solubilize dye molecules. The polyvalent salts are able to flocculate the micelles and help in their subsequent removal. The removal of dye was analyzed by the use of a UV/Visible spectrophotometer. Different factors such as the effect of change in concentration, pH, temperature, contact time, and electrolyte were studied to evaluate the adsorption characteristics and removal efficiency of the process. The data obtained was further used to study the mechanism of adsorption with the help of various models e.g., Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R). The kinetic parameters were also calculated by employing pseudo-1st and pseudo-2nd order kinetic models. Furthermore, thermodynamic calculations were performed to determine the change in Gibb’s free energy (ΔGo), enthalpy (ΔHo), and entropy (ΔSo). The results make it evident that the micellar flocculation-based adsorptive removal is an excellent and sustainable approach for the treatment of wastewater.

Kinetic insights on wet peroxide oxidation of caffeine using EDTA-functionalized low-cost catalysts prepared from compost generated in municipal solid waste treatment facilities

Nowadays, sorted organic fraction of municipal solid waste is typically treated by anaerobic digestion processes, resulting therein a solid stream, further processed to obtain compost, whose production is higher than the existing demand as fertilizer. The current work proposes an alternative strategy for the recovering of compost through the production of low-cost catalysts by calcination (1073 K) and sulfuric acid treatments, followed by sequential functionalization with tetraethyl orthosilicate (TEOS) and ethylenediamine tetraacetic acid (EDTA). Activity and stability of the catalysts are assessed in the wet peroxide oxidation of synthetic wastewater effluents contaminated with caffeine, a model micro-pollutant, achieving its complete removal after 6 h at 353–383 K and catalyst loads of 0.5–2.5 g L−1. The increase of the catalytic activity of the materials upon functionalization with TEOS and EDTA is demonstrated and a kinetic modeling of caffeine degradation and hydrogen peroxide consumption with the best catalyst is assessed by pseudo-first power-law rate equations.

Micellar flocculation for the treatment of synthetic dyestuff effluent: Kinetic, thermodynamic and mechanistic insights

This research work is an attempt to evaluate the role of micellar flocculation (MF) for the treatment of dye-contaminated water. Solubilization of dye by organized assemblies of anionic surfactants and its subsequent complexation with the metal cations during flocculation has been found as the active phenomena in this treatment methodology. Base soap (BS) being a mixture of anionic surfactants along with the salt of the divalent cation (Ca2+) was employed to capture and separate the reactive dye, reactive red 195 (RR-195), in the form of flocs at optimized concentrations of soap, dye, and flocculant. The effect of contact time, temperature, pH, and electrolyte has also been investigated to figure out the optimum conditions necessary to perform this adsorptive removal. The surface characteristics of adsorbent and favorability of adsorption were evaluated with the help of different isotherm models i.e., Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin. Furthermore, kinetic and thermodynamic calculations were performed for a better understanding of the nature of the said removal. Herein, the results reveal that this removal process is spontaneous, favorable, and exothermic. The excellent removal of RR-195 (≈99%) through micellar flocculation suggests that it’s an economical, sustainable, and efficient approach for the treatment of industrial effluent containing dyes.

A new magnetic composite with potential application in boron adsorption: Development, characterization, and removal tests

In this work, a new magnetic composite, with good performance in the adsorption of boron from aqueous solutions, is proposed. The composite was prepared from CoFe2O4 and MgO precursors, which were produced by the sol-gel method using orange juice residues. X-ray diffraction, scanning electron microscopy, infrared spectroscopy, 57Fe Mössbauer spectroscopy, and magnetization measurements have indicated that the ferrimagnetic CoFe2O4 nanocrystalline phase is immersed in the MgO matrix. The magnetic composite was applied to boron compounds removal from synthetic effluents (with boron concentrations up to 20 mg L−1), showing up to 92% removal capacity. After the boron adsorption process on the MgO surface, X-ray diffraction, scanning electron microscopy, and infrared spectroscopy results have shown the formation of crystalline Mg(OH)2 (with needle-like structures), and 57Fe Mössbauer spectroscopy has indicated that the fraction of Fe+3 ions in the nanograin surfaces was changed in comparison with the pristine adsorbents. Three possible boron adsorption mechanisms are suggested: adsorption at the Mg(OH)2 crystallite surface, adsorption through the formation of Fe–O–B bonds, and adsorption by an amorphous Mg(OH)2 gel. The pseudo-first order model was successfully used to fit the kinetic adsorption curves, whereas the Freundlich model has described the isotherms, thus indicating a heterogeneous distribution of adsorption heat and affinities. The composite was found to adsorb about 6% more boron than pure MgO and can be recoverable with a permanent magnet.

Green extraction based on emulsion liquid membranes: Removal of Cr (III) from synthetic effluents

The presence of heavy metals in wastewaters originating from different industries is of great concern since they can enter into the food chain. Therefore, of the several existing procedures, “green extraction” methods have gained increased interest since solvent volumes are significantly reduced. In this regard, liquid–liquid extraction has been applied to recover metals from industrial effluents. The objective of this study was to investigate chromium removal from synthetic wastewater using emulsion liquid membranes (ELM). The contaminant removal capacity was 16.27 mg Cr (III)/g of sodium dodecyl sulfate. The emulsion phase was reused 6 times obtaining removal rates of Cr (III) above 65%. The great advantage of emulsion systems is their reduced risk to the environment, since it is possible to reduce the volume of organic solvents used and also to reuse these solvents in the process.

Pilot-scale study on photodegradation of benzophenone-3 and benzophenone-8 ultraviolet filters enriched synthetic effluent

Ultraviolet (UV) filters are the significant ingredients of sunscreens, cosmetics, and other personal care products. They are used to guard human body against harmful UV radiations present in sunlight. In recent years, due to their excessive use, high UV filters concentrations have been detected in swimming pools. The present study was aimed to photodegrade the two most commonly used UV filters, namely benzophenone-3 (BP-3) and benzophenone-8 (BP-8) using pilot-scale advanced oxidation process (AOP) treatment. The photodegradation of selected UV filters was optimised under various oxidant systems viz. hydrogen peroxide (H2O2), potassium peroxomonosulphate (PMS), and potassium peroxodisulphate (PDS). In the absence of oxidant, the photodegradation rate of BP-3(58.25%) was higher than BP-8 (48.31%). The generation of SO4.- and.OH radicals enhanced the degradation of UV filters. Similar degradation trend (UVC < UVC/PMS < UVC/H2O2 < UVC/PDS) was observed for both BP-3 and BP-8 in presence of oxidants. However, on comparing the efficiency, the photodegradation of BP-3 was better in most of the UVC/oxidant systems. Generation of degradation by-products viz. bezonic acid, 2,4-dimethyl benzaldehyde, 2-methylphenyl benzoate, and benzyl alcohol was confirmed through mass spectroscopic (MS) analysis. Degradation mechanism of UV filters was proposed and overall process cost was estimated. The findings of the current study could be a baseline for treating swimming pools water.

Remediation of phenanthrene & cadmium co-contaminated soil by using a combined process including soil washing and electrocoagulation

ABSTRACT In the present work, the application of a combined process including soil washing by using the non-ionic surfactant Tween 80 and EDTA and electrocoagulation in remediation of phenanthrene (PHE) and cadmium (Cd) contaminated soils was investigated. In order to examine the effect of operational parameters on the efficacy of the process, Response Surface Methodology under Box–Behnken design was applied in both stages. Tween 80 solution and EDTA with concentrations of 1000–3000 and 1000–2000 mg L−1 respectively, at liquid/soil (L/S) ratio of 10, 20, and 30 v/w in a time interval of 2–24 h, were applied to remove PHE and Cd simultaneously from the co-contaminated soil. PHE and Cd extraction efficiency were mostly influenced by Tween 80 and EDTA concentration, respectively (P value< 0.0001). L/S ratio also improved the removal efficiency of the contaminants significantly (P value< 0.0001). Soil washing process under the optimal operational conditions of the surfactant concentration 3000 mg L-1, EDTA concentration 2000 mg L-1, L/S ratio 30 v/w and washing time = 2 h resulted in the removal efficiency of 59.284 ± 4.347% and 74.35 ± 3.632% for PHE and Cd, respectively. Electrocoagulation of the adjusted synthetic effluent based on the optimal operational conditions of soil washing phase was carried out at pH values of 3–11, with a voltage of 10–30 v, and in reaction time of 45–90 min. The results demonstrated that the removal efficiency of both contaminants was mostly enhanced by increasing pH (P value< 0.0001). The factor of voltage had also a positive significant effect on the responses (P value< 0.0001). The presented optimum conditions for electrocoagulation including pH of 11, a voltage of 30 v, and reaction time of 45 min provided a removal efficiency of 94.85 ± 1.715 and 100% for PHE and Cd respectively.

Anodic oxidation of synthetic refinery effluent on lead anode: mass transport and charge rate balance.

A synthetic wastewater based on Algiers refinery real effluent was prepared and treated using anodic oxidation. Full factorial plan design was used to conduct the statistical analysis of the results. The aim of the study was to assess the interaction between current density (CD) and stirring degree (SD), and quantify their effects on chemical oxygen demand (COD) removal and electric energy specific consumption (EESC). With an initial COD of 487 mg/L, pH of 5.5 and 0.05 M of Na2SO4 as supporting electrolyte, it was found that a 55 rpm stirring degree variation led to a substantial gain in COD removal and energy consumption: 6% and 8.5 KWh/kg, respectively. Current density was found to have a different effect on removal efficiency within the applied stirring domain, and mass transport coefficient (km) is inversely correlated to energy consumption. A theoretical model describing the process was reviewed and the relation between concentration, hydrodynamics and applied current was emphasized.

Recovery of Cr(III) from Tannery Effluents by Diafiltration Using Chitosan Modified Membranes

The selective recovery of chromium remaining in tannery effluents after the leather tanning process is highly desirable to potentiate its reuse, simultaneously minimizing the ecotoxicity of these effluents. To the best of our knowledge, this work evaluates for the first time the ability of a chitosan-based membrane for selective recovery of chromium from a tannery wastewater by subsequent diafiltration and selective chromium desorption, envisaging their integration after tannery wastewater treatment by reverse osmosis (RO). A polyethersulfone (PES) microfiltration membrane top-coated with a chitosan layer (cs-PES MF022) was used for selective recovery of Cr(III), from concentrate streams obtained by treatment of synthetic and real tannery effluents through reverse osmosis (RO), through a diafiltration process. The diafiltration of the RO concentrates was conducted by an intermittent addition of water acidified to pH 3.6. The prepared cs-PES MF022 membranes were able to retain 97% of the total mass of Cr(III) present in the RO concentrates, from a real tannery effluent, with a selectivity of 4.2 and 5 in reference to NH4+ and Cl−, respectively, 12.9 and 14.6 in reference to K and Na, and &gt;45 in reference to Mg, Ca, and S. Such a high selectivity is explained by the preferential adsorption of Cr(III) onto chitosan, and by the relatively high permeability of cs-PES MF022 membranes to the other ionic species. Proof of concept studies were performed to investigate the desorption of Cr(III) at pH 2 and 5.8. A higher Cr(III) desorption degree was obtained at pH 2, leading to a final solution enriched in Cr(III), which may be re-used in tannery operations, thus improving the process economy and reducing the hazardous impact of the effluents discharged by this industry.

Removal of antibiotic rifampicin from aqueous media by advanced electrochemical oxidation: Role of electrode materials, electrolytes and real water matrices

One of the most commonly detected classes of pharmaceutical products in aquatic environments are antibiotics and their effective removal in sewage treatment plants is limited due to their refractory features. In this context, electrochemical technologies could be an alternative to decrease the pollution level and promote the complete elimination of antibiotics in water. For this reason, the electrochemical treatment of a synthetic effluent as well as different real water matrices polluted with antibiotic rifampicin was investigated, using different electrode materials (anodes: boron doped diamond, (BDD), Pt and PbO2; and cathodes: carbon felt (CF), graphite (Gr), stainless steel (SS) and titanium (Ti)). Effects on the variation of applied current density (j) and supporting electrolyte were examined during the degradation of the antibiotic. Comparative studies have clearly showed that the degradation of rifampicin had better results by using BDD and CF as anode and cathode, respectively, where the process efficiency increased when an increase on the j was attained. Complete color removal was achieved at all j applied (chromophore rifampicin group gives a red-orange color for solutions), whereas only at higher j leads to complete organic matter (in terms of chemical oxygen demand (COD)) removal. For a selected cathode, the efficiency of the anode materials follows the trends BDD>PbO2>Pt, whereas that of cathode follows CF>Ti>SS≈Gr for a selected anode material. Using Na2SO4, Na2CO3 or NaCl, the production of strong secondary oxidant species was favored, promoting the oxidation of dissolved organic matter in synthetic effluents. Meanwhile, when the BDD/CF electrochemical cell was employed with different real water matrices, the degradation and mineralization of the drug was independent of this parameter. Oxalic, acetic, fumaric and maleic acids were the final organic byproducts of rifampicin degradation with the release of heteroatom N under NO3‒ and NH4+ forms.

Textile wastewater treatment using horizontal flow constructed wetland and effect of length of flow in operation efficiency

Textile wastewater treatment is a challenging process due to its high-intensity color and high COD value. In this study, the effect of design parameters of constructed wetlands in the treatment of synthetic textile dyeing bath effluent using horizontal flow constructed wetlands was explored. The effect of length of flow through the wetlands and hydraulic retention time in pollutant removal were analyzed. Two wetland reactors, one baffled, and the other non-baffled reactors were operated with varying lengths of flow and HRT (3 days to 7 days). It was observed that the maximum color (72 ± 2%) and COD removal (85 ± 3%) occurred in the baffled reactor at a dye loading rate of 1.15 g/m2 d and COD loading rate of 10.3 g/m2 d. The pH change and sulfate removal rates (34 ± 2%) at a sulfate loading rate of 2.8 g/m2 d were similar in both reactors. Overall, the length of flow affected slightly the performance of wetland reactors for color and COD removal. The study suggests that there exists a need for the development of proper design parameters for the effective use of constructed wetlands in the treatment of wastewater.

Use of kaolin as a potential low-cost adsorbent for the removal of reactive blue BF-5G dye

The objective of this work was to use kaolin as an adsorbent for synthetic effluent, based on the reactive blue dye BF-5G. Several analytical techniques were used to investigate the material's crystallinity, morphology, specific surface area and fundamental functional group of kaolin. In sequence, different pH values were studied using a finite bath system. In investigating the influence of pH, the adsorbent used showed superior performance at a pH value equal to 1. From this optimal value, kinetic studies were carried out with the ideal conditions of pH, concentration and adsorbents (pH = 1, C0 = 50 mg/L and kaolin used as adsorbent). The adsorption percentage is maximum at pH 1 and decreases with the basic strength of the dye solution.

Evaluation of zinc adsorption through batch and continuous scale applying Bayesian technique for estimate parameters and select model

This work aims to study the efficiency of zinc adsorption onto granular-activated carbon, predicting the mathematical models that best describe the adsorption behavior in a fixed bed column. First, batch scale experiments were performed to evaluate the influence of pH (3 to 6), contact time (5 to 60 min), and absorbent concentration (5 to 25 g L−1) using synthetic effluent. Fixed bed column experiments were performed by varying the adsorbent concentration (10, 13, 20, and 40 g L−1) and the effluent flow rate (15 and 20 mL min−1). Markov Chain Monte Carlo and Bayesian criteria information were applied to describe the phenomena using Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips, Toth, Khan, Radke-Prausnitz, for isotherm models, and Thomas; Yoon-Nelson; Yan; Clark models for breakthrough curve. Adsorption operating best conditions were pH 5, 20 g L−1 of solid, and 50 min of contact time. These parameters allowed 80% of Zn removal, being better described by the Tempki model. In tests on a pilot plant, the Yan model was able to predict the second-order kinetic model, with an increase in the effluent flow and a 50% increase in the bed saturation time with a greater amount of adsorbent solid.

Photocatalytic Advanced Oxidation Processes for Neutralizing Free Cyanide in Gold Processing Effluents in Arequipa, Southern Peru

Cyanide (CN−) from gold processing effluents must be removed to protect human health and the environment. Reducing the use of chemical reagents is desirable for small centralized and decentralized facilities. In this work, we aimed to optimize the use of ultraviolet (UV) radiation coupled with hydrogen peroxide (H2O2) to enhance the rate and extent of CN− removal in synthetic and actual gold processing effluents, from one centralized and one decentralized facility in southern Peru. Bench-scale studies conducted using H2O2 and ambient UV showed no significant effects on CN− destruction; however, experiments with higher UV intensity and H2O2 accelerated free CN− degradation. When a 1:1 stoichiometric ratio of CN−:H2O2 was tested, the highly concentrated effluent (1 g CN−/L) had a slower pseudo first-order rate constant (k = 0.0066 min−1) and took ~5 h longer to reach 99% destruction, compared with the low concentration effluent (100 mg CN−/L; k = 0.0306 min−1). Lastly, a TiO2 photocatalyst with low stoichiometric CN−:H2O2 ratios (1:0.1 and 1:0.2), in a compound parabolic solar concentrator, was tested to investigate the degradation of a high concentration effluent (1.28 g CN−/L). These results show a significant improvement to degradation rate within a 20 min period, advancing treatment options for mineral processing facilities.

Simultaneous removal of lead and cyanide from the synthetic solution and effluents of gold processing plants using electrochemical method

Hazardous effluents containing heavy metals and toxic compounds such as cyanide are among the contaminants produced annually by mining activities. In this study, the electrocoagulation method was used to simultaneously remove cyanide and lead from the synthetic and natural effluents of a gold mine processing plant. The effect of four parameters including initial pH, current intensity, reaction time, and electrode arrangement was investigated under different conditions. Results indicated that by increasing the current intensity to 300 mA at pH = 9 for 40 min, the cyanide and lead removal efficiencies were increased to 91% and 74%, respectively. In addition, the highest cyanide and lead removal efficiencies at pH = 9 and a current intensity of 300 mA after 40 min were 97% and 81%, respectively. The removal of 100% of cyanide in the presence of lead using Fe as the anode electrode can be attributed to the higher oxidation rate of iron than aluminum and the formation of more flocs in the solution The removal of 94% of lead in the presence of cyanide using aluminum as the anode electrode can be related to pH limitations applied for the simultaneous removal of lead and cyanide as well as the dissolution of aluminum species at this pH, preventing its complete removal. Overall, it can be concluded that the electrocoagulation method is an effective technique for simultaneous removal of lead and cyanide from contaminated effluents.

TREATMENT OF A TEXTILE WASTEWATER USING AN ELECTROCOAGULATION REACTOR POWERED BY PHOTOVOLTAIC SOLAR ENERGY

The textil industry uses a variety of dyes in the stage of coloring. The liquid effluent resulting at the end of the process has high turbidity and a large chemical oxygen demand. If these byproducts are dumped into natural water bodies, even in small quantities, they may produce damage to the aquatic environment and to human health. Electrocoagulation is becoming an efficient technique for the removal of pollutants from industrial effluents, it is easy to operate, and produces little sludge at the end of the treatment. In the present study, the use of an electrocoagulation reactor with aluminum electrodes proved efficient for turbidity removal from synthetic industrial effluents. The use of a solar plate of photovoltaic electricity for the functioning of the reactor was evaluated. Ideal time of treatment was 20 minutes. The use of a conventional energy source removed 63% of the turbidity. Using the voltaic solar energy source, a removal of 72% of turbidity was attained. We conclude that it is possible to use the alternative solar energy source in order to minimize costs resulting from electrical energy consumption, and, at the same time, to obtain the best results in the removal of pollutants.