Synthetic Wastewater Solutions Research Articles

Adsorption of Chromium (VI) from Wastewater by Anion Exchange Resin

Strong anion exchange resin (Spectra/Gel IE 1x8) has been investigated as adsorbent for the efficient removal of Cr(VI) ions from synthetic wastewater solutions. Batch experiments were conducted with initial Cr(VI) ions concentration ranging from 25-300 mg/L. Different parameters influencing Cr(VI) adsorption process such as; solution pH, Cr(VI) and adsorbent concentration and contact time were investigated. Results obtained revealed that Cr(VI) was successfully retained by the resin. Equilibrium was established within 30 minutes for initial Cr(VI) concentration up to100 mg/L. The equilibrium data for adsorption of Cr(VI) was fitted with both Langmuir and Freundlich isotherms, however, Langmuir isotherm model was found to be more suitable for the Cr(VI) adsorption and maximum adsorption capacity of the Cr(VI) was found to be 173.8 mg/g. The adsorption process followed second order kinetics. The resin was regenerated by using 4M NaOH as an eluent and retained Cr(VI) adsorption efficiency higher than 83% after three regeneration cycles.

Chromium ions (Cr6+ & Cr3+) removal from synthetic wastewater by electrocoagulation using vertical expanded Fe anode

The performance of an innovative batch cell design in removing chromium ions (Cr6+ & Cr3+) from synthetic wastewater solutions by electrocoagulation has been investigated. The cell consists of two concentric vertical cylindrical Fe-electrodes; the outer electrode is a cylindrical solid Fe-cathode which is supported in the vessel wall, whereas the inner electrode is an expanded cylindrical Fe-anode. The distance between the two electrodes is 0.5cm apart. The performance of the present cell has been expressed in terms of % removal of (Cr6+ & Cr3+). The effect of key parameters such as electrolysis time, current density, pH, initial (Cr6+ & Cr3+) ions concentration, NaCl concentration and electrode connection on the % removal (Cr6+ & Cr3+) has been investigated. The study revealed that as current density increases, % Cr3+ removal slightly increases, whereas % Cr6+ removal slightly decreases. As NaCl concentration increases, % Cr6+ removal increases gradually, while % Cr3+ removal increases up to 1g/l and decreases beyond this value. Maximum % Cr6+ removal occurs at pH 4.5, whereas maximum % Cr3+ removal occurs at pH 8. As the initial concentration of Cr ions increases, % Cr removal decreases. Monopolar parallel electrode connection is the optimum electrode connection. Power consumption evaluation of the present cell design reveals that power consumption increases as current density increases, while it decreases as NaCl concentration increases. Power consumption calculations show that at optimum conditions of Cr3+ removal by Electrocoagulation (EC) a 10.98kWh/kg (1.09kWh/m3) is required whereas at optimum conditions of Cr6+ removal by Electrocoagulation (EC) a 16.14kWh/kg (2.299kWh/m3) is required.

ZnO-nanoparticles thin films synthesized by RF sputtering for photocatalytic degradation of 2-chlorophenol in synthetic wastewater

Zinc oxide nanoparticle thin films were synthesized on glass substrate by radio-frequency magnetron sputtering (RF Sputtering) technique. The thin films were characterized and tested for optical properties by using different techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV–visible spectrophotometry and fluorescence spectrofluorophotometry. The produced nanoparticle ZnO thin films were investigated as photocatalyst for degradation of 2-chlorophenol (2-CP) in synthetic wastewater solutions under UV irradiation. Complete degradation of 2-CP was achieved by ZnO thin film (200nm thickness) within 3h at solution pH 3. The photocatalyst retained its high efficiency even after three reuse cycles.

Removal of Copper Ions from Simulated Wastewaters Using Different Bicomponent Polymer Membranes

The main goal of this study was to explore the suitability and performance of bicomponent polymer membranes based on acrylonitrile copolymers-polyvinyl alcohol (PVA) mixtures and small quantities of anion (Purolite A100) or cation exchange resin (Purolite C150), prepared by phase inversion. Membranes were used for copper removal from synthetic wastewater solutions. A three detachable cylindrical compartment electrodialysis cell without recirculation of the electrolytes and synthetic solutions of various concentrations, similar to a copper electrowinning electrolyte, were used. The electrodialysis unit operates under galvanostatic control. The effect of pH on electrodialysis separation of Cu2+ and on the solution conductivity has been also investigated. The laboratory electrodialysis cell performance was evaluated in terms of percent of extraction (pe) and current efficiency (ce). Experimental results showed that the ionic transfer in electrodialysis cell was especially affected by concentration. The highest values for the pe (>81 %) and the ce (>25 %) of copper ions were obtained at maximum concentration in copper ions (3 g/L), indicating a better performance of the ion extraction. The transport of copper ions was also correlated with flux data. The ion exchange membranes were characterized using FT-IR spectroscopy, ESEM, and electrochemical impedance spectroscopy.

Enhancement of photocatalytic activity of zinc/cobalt spinel oxides by doping with ZrO2 for visible light photocatalytic degradation of 2-chlorophenol in wastewater

Abstract ZrO2-doped ZnCo2O4 nanoparticles were synthesized by hydrothermal coprecipitation of sulphate precursors with Zn/Co atomic ratio of 0.5 followed by addition of 0.05 mmol of ZrO2 precursor and calcination at 250–650 °C for 3 h. Several characterization tools such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV–visible diffuse reflectance spectroscopy (UV–vis-DRS) were used for the morphological structure, chemical composition and optical properties of the catalysts. Doping with ZrO2 appeared to stabilize the ZnCo2O4 phase and suppress ZnO phase formation as evidenced by XRD. The produced ZrO2-doped ZnCo2O4 nanoparticles were evaluated as catalyst for visible light photodegradation of 2-chlorophenol (2-CP) in synthetic wastewater solutions. Presence of ZrO2 in the ZnCo2O4 structure was responsible for a significant shift in the UV absorption spectrum toward visible region and resulted in enhancing the visible light photocatalytic activity. The photocatalytic experiments were performed in a batch reactor under 150 W visible light irradiation (λ > 400 nm). Parameters affecting the photocatalytic activity of the catalyst such as the catalyst dose, solution pH, and 2-CP concentration were investigated and evaluated. Results indicated efficient degradation of 2-CP, the highest removal % was achieved by catalyst calcined at 350 °C.

InVO 4/TiO 2 composite for visible-light photocatalytic degradation of 2-chlorophenol in wastewater

InVO 4/TiO 2 composite was synthesized via amalgamation of InVO 4 with TiO 2 (Degussa P-25) powders. Application of the produced composite was evaluated as a catalyst for visible-light photocatalytic degradation of 2-chlorophenol (2-CP) in synthetic wastewater solutions. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy energy dispersive X-ray microanalyses and nitrogen physisorption. The degradation of 2-CP was affected by solution pH, light intensity, photocatalyst dosage and 2-CP initial concentration. InVO 4/TiO 2 showed higher photocatalytic degradation of 2-CP as compared with Degussa P-25 TiO 2. Complete degradation of 2-CP was achieved with the InVO 4/TiO 2 catalyst under optimized conditions (1 g/L catalyst with a pollutant concentration of 50 mg/L at solution pH 5 and irradiation time of 180 min). Comparatively, 2-CP degradation efficiency of 50.5% was achieved with the TiO 2 (Degussa P-25) at the same experimental conditions. The study confirmed that InVO 4/TiO 2 has high potential for degradation of 2-CP from wastewater under visible-light irradiation.

Removal of Heavy Metal Quaternary Cations Systems on Zeolite A and X Mixtures Prepared from Local Kaolin

The use of a mixture of zeolites A and X was utilized to study the selectivity and the removal efficiency of a mixture of a quaternary cations solution containing Ca2+, Cu2+, Co2+, and Ni2+. The selectivity varied according to the mixture content. The total amount removed was found to follow the second order equation. Different mixtures of zeolites were examined for the removal efficiency of quaternary system of cations. The normalized selectivity varied according to the percent of the mixture. Pure zeolite A showed a non‐selective behavior while zeolite X was highly selective for Cu2+. The in‐between mixtures showed a variety of selectivity. The % mixture of two zeolites could be used for the selection of optimum conditions for the actual cases based on % of cations. A program was written to calculate the % removal of each cation in the solution. The mixture was examined on several synthetic wastewater solutions containing the quaternary system of these cations and on a real wastewater sample. It is found that the program could expect the % removal of the quartenary cation with more than 99% precision.

Pt nanoparticles/TiO2 for photocatalytic degradation of phenols in wastewater

Pt nanoparticles/TiO 2 catalysts were prepared and evaluated for UV-photocatalytic degradation of phenol and 2-chlorophenol (2-CP) in synthetic wastewater solutions. The catalysts were synthesized by immobilizing colloidal Pt nanoparticles onto titanium dioxide (rutile TiO 2). Analytical techniques, such as standard Brunauer–Emmett–Teller isotherms, X-ray diffraction, transmission electron microscope, were utillized for investigating the specific surface area, structure, and particle size distribution of the catalysts and its components. The photocatalytic activities of both phenol and 2-CP solutions were studied in a 1 L batch photoreactor independently, under 450 W UV irradiation. Samples were drawn at regular intervals and residual concentration of phenol and 2-CP in the samples was analysed using an UV-visible spectrophotometer. Parameters controlling the photocatalytic process, including catalyst concentration, solution pH, and initial phenol (2-CP) concentration, were investigated. The obtained results revealed that Pt/TiO2 showed higher photocatalytic degradation for both phenol and 2-CP pollutants in solution (as compared to the rutile TiO2). The degradation efficiencies of 87.7% and 100% were obtained for phenol and 2-CP, respectively, under optimized conditions (0.5 g/L catalyst with a pollutant concentration of 50 mg/L after irradiation time of 180 min).

Phenol Removal Process Development from Synthetic Wastewater Solutions Using a Polymer Inclusion Membrane

This paper presents the results concerning the first use of a polymer inclusion membrane (PIM) for the removal and transport of phenol from an aqueous solution and polluted water. The PIM contains Cyanex 923 as the carrier, cellulose triacetate (CTA) as the base polymer, and o-nitrophenyl pentyl ether (ONPPE) as a plasticizer. The effects of variables on the transport percentage of phenol have been studied. These variables include the concentration of the carrier and the plasticizer in the membrane, pH of the aqueous phase, and the concentration of NaOH in the stripping phase. This study shows that PIM composition has a great influence in phenol recovery, while the pH of the feed phase is a determining factor for the transport of phenol. In optimal conditions (PIM: 1 cm3 ONPPE/g CTA, 0.5 M of Cyanex 923; feed phase: pH 2; stripping phase: NaOH 0.25 M), it is possible to transport 85% of phenol present in both the water lab feed phase and polluted water. Chemical oxygen demand (COD) shows that only 4.3% of organic compounds other than phenol are transported to the stripping phase, which indicates that the process is highly discriminative for phenol, even in extremely contaminated water.

Treatment of Clinoptilolite as an Adsorbent for the Removal of Copper Ion from Synthetic Wastewater Solution

Clinoptilolite was treated with HCl for the purpose of using it as adsorbent for the removal of Cu2+ from the synthetic wastewater. The treated clinoptilolite was characterised using XRF and SEM to determine its chemical composition and morphology, respectively. The results showed that treatment of clinoptilolite with HCl affects its chemical composition and morphology. The critical parameters affecting the adsorption of Cu2+ were also investigated by utilizing clinoptilolite natural zeolite as the potential adsorbent at various initial concentrations of the copper ion in the synthetic wastewater. The analyses of the results obtained revealed that the adsorption of Cu(II) from synthetic water is strongly dependent on pH, temperature, and contact time and mass of the adsorbent. It was found that pH of four, contact time of 75 min, temperature of \({90\, ^{\circ}}\) C, and mass of adsorbent of 10 g are the best conditions for the removal of Cu2+ from the synthetic wastewater. The equilibrium sorption isotherms were analyzed by the Langmuir and the Freundlich isotherms and the analyses of the results showed that Freundlich isotherm described the adsorption process better than the latter. The equilibrium data showed an endothermic nature of adsorption. The thermodynamic parameters obtained from the equilibrium data indicated that the adsorption process is endothermic with increase in entropy of the solid–solution interface during the adsorption of cation onto the clinoptilolite.

Titania-supported silver-based bimetallic nanoparticles as photocatalysts

Photocatalytic process has shown recently a great potential as an environmental friendly and clean remediation technology for organic pollutants in wastewater. This work described the synthesis of silver-based bimetallic nanoparticles using colloid chemistry and the subsequent immobilization onto titania to form composite photocatalytic materials (titania-supported Ag-Pt nanoparticles). The photocatalysts were characterized by X-ray diffraction, electron microscopy, and nitrogen physisorption. The catalytic activity of the photocatalysts was evaluated by photocatalytic degradation of phenol and 2-chlorophenol (2-CP) in synthetic wastewater solutions. The photocatalytic processes were conducted in a batch photoreactor containing appropriate solutions of phenol and 2-CP with UV irradiation of 450 W. UV-visible spectrophotometer was used for analyzing the concentration of phenol and 2-CP in solutions. Parameters affecting the photocatalytic process such as the solution pH, phenol and 2-CP concentrations, and catalyst concentration were investigated. The results obtained revealed that TiO(2)-supported Ag/Pt nanoparticles showed a higher activity for UV-photocatalytic degradation of both phenol and 2-CP pollutants in the solution (as compared to the plain rutile TiO(2)). The photodegradation processes were optimized by the 0.5-g/L catalyst with a pollutant concentration of 50 mg/L for all the samples. Complete degradation for both phenol and 2-CP was achieved after 120 min.

Chemically Modified Crop Residues as a Low-Cost Technique for the Removal of Heavy Metal Ions from Wastewater

Batch adsorption experiments were carried out to evaluate the effect of type of crop residues and chemical pretreatment solutions on the removal efficiency of heavy metal ions at different concentrations of synthetic wastewater solutions. Rice straw, cotton stalks, and maize stalks were pretreated with different solutions (i.e., sulfuric acid, oxalic acid, sodium hydroxide, and distilled water as the control treatment) in order to increase their metal-binding capacity. Results indicated that cotton stalks were the best biosorbent material according to their efficiency in removal of heavy metal ions. Sodium hydroxide was the best chemical pretreatment method for stimulating the biosorption capacity of crop residues. Ions of Pb2+ had the highest biosorption ratio among all competitive ions, whereas Mn2+ ions had the lowest. The removal efficiency decreased as the concentration of heavy metal ions increased in aqueous solutions. Sorption equilibrium isotherms could be described by the Langmuir model in most cases, whereas an isotherm of S shape was observed in other cases, which did not follow the Langmuir isotherm model. In conclusion, cotton stalks pretreated with sodium hydroxide could be used as an efficient technique for wastewater remediation prior to irrigation due to its low-cost, little processing, and high biosorption capacity.

Nanoporous Lanthanum Tungstate: A Viable Adsorbent for Heavy Metals and Organic Pollutants

AbstractRemoval of heavy metal cations from synthetic and industrial electroplating effluents by means of mesoporous lanthanum tungstate sorbents was thoroughly investigated. Three types of such sorbents, namely I‐LT, II‐LT and III‐LT, uncalcined and calcined, were produced and characterized by means of X‐ray diffraction, nitrogen sorption isotherms and thermogravimetry analysis (TGA). Results of the experiments for chromium, copper, mercury, iron and lead removal from both synthetic and real industrial wastewater solutions, using these novel sorbents, exhibit promising. Details of this new approach towards wastewater treatment have been discussed and the potentials of technological advancement using mesoporous lanthanum tungstate for environmental purposes addressed. Comparison with the literature shows superiority of the produced adsorbents over reported products.

Polymer-enhanced ultrafiltration process for heavy metals removal from industrial wastewater

Recently, the complexation–ultrafiltration technique has been shown to be a promising technique for removal of heavy metals in solution. In this study, a polymer-enhanced ultrafiltration process has been investigated for removal of toxic heavy metals such as Cu(II), Ni(II), and Cr(III) from synthetic wastewater solutions. Carboxy methyl cellulose as a water-soluble polymer was used for complexing the cationic forms of the heavy metals before filtration. The size of the complex has to be larger than the pores of the selected membrane so the complex can be retained. Permeate water is then purified from the heavy metals. Filtration experiments were performed with ultrafiltration membrane system, equipped with a polyethersulfone membrane with a 10,000 Da cut-off. The pressure was fixed at 1 bar with a permeate flow rate of 7.5 L/h. Different parameters, affecting the percentage rejection of the metals, such as pH, metal ion concentration, CMC/metal ratio, and permeate flux ( F) have been investigated. Metal rejection in aqueous solution containing Ni(II), Cu(II) and Cr(III) ions simultaneously was also evaluated. Results obtained revealed that the maximum percentage of the metal rejection was achieved at pH ≥ 7 with increasing of the CMC concentration.

Different calibration methods of a microbial BOD sensor for analysis of municipal wastewaters

On the base of diffusion limited amperometric oxygen sensor (the Clark-type oxygen sensor) a microbial BOD sensor was constructed and the dependence of output signal of device on wastewater biochemical oxygen demand (BOD) was studied. Calibration of BOD sensor was performed in steady-state and dynamic regime of measurements in OECD synthetic wastewater solutions. Results showed broader detection area (up to 230mgBOD7L−1) as well as shorter response and regeneration times in dynamic regime of analysis of output signal. The data acquired by steady-state method showed better repeatability, especially in the estimation of BOD7 of real wastewaters. After calibration the BOD sensor was used for quick BOD estimations of municipal wastewaters.

Biohydrogen production from wastewater by Clostridium beijerinckii: Effect of pH and substrate concentration

Abstract An investigation of biological hydrogen production from glucose by Clostridium beijerinckii was conducted in a synthetic wastewater solution. A study examining the effect of initial pH (range 5.7–6.5) and substrate loading (range 1–3 g COD/L) on the specific conversion and hydrogen production rate has shown interaction behaviour between the two independent variables. Highest conversion of 10.3 mL H 2 /(g COD/L) was achieved at pH of 6.1 and glucose concentration of 3 g COD/L, whereas the highest production rate of 71 mL H 2 /(h L) was measured at pH 6.3 and substrate loading of 2.5 g COD/L. In general, there appears to be a strong trend of increasing hydrogen production rate with an increase in both substrate concentration and pH. Butyrate (14–63%), formate (10–45%) and ethanol (16–40%) were the main soluble products with other volatile fatty acids and alcohols present in smaller quantities.

Influence of airflow rate and substrate nature on heterogeneous struvite precipitation

In wastewater treatment plants a hard scale consisting of struvite crystals can be formed, in pipes and recirculation pumps, during anaerobic digestion of wastewater. This study was conducted to evaluate the effect of airflow rate and substrate nature on nucleation type, induction period and supersaturation coefficient during struvite precipitation. A crystallization reactor similar to that designed for calcium carbonate precipitation was used. The pH of synthetic wastewater solution was increased by air bubbling. Experimental results indicated that the airflow increased heterogeneous precipitation of struvite. The susceptibility to scale formation was more important on polyamide and polyvinyl chloride than on stainless steel. In all cases, X‐ray diffraction and infrared spectroscopy showed that the precipitated solid phase was solely struvite. No difference in crystal morphology was observed. However, at similar experimental conditions, the particle size of struvite was higher for stainless‐steel material than that for plastic materials.

Removal of H2S and volatile organic sulfur compounds by silicone membrane extraction

AbstractBACKGROUND: This study explores an alternative process for the abatement and/or desulfurization of H2S and volatile organic sulfur compounds (VOSC) containing waste streams, which employs a silicone‐based membrane to simultaneously remove H2S and VOSC. An extractive membrane reactor allows the selective withdrawal of VOSC and H2S simultaneously from the waste stream, while preventing direct contact between the waste stream and the absorbing solution and/or the biological treatment system. The influence of the sulfur compounds, membrane characteristics, extractant and pH was studied.RESULTS: Sulfide and the VOCS studied, i.e. methanethiol (MT), ethanethiol (ET) and dimethylsulfide (DMS) were removed from the synthetic wastewater using a silicone rubber membrane. Methanethiol showed the highest (8.72 × 10−6 m s−1) overall mass transfer coefficient (kov) and sulfide the lowest kov value (1.23 × 10−6 m s−1). Adsorption of the VOCS into the silicone membrane reduced the overall mass transfer coefficient. The kov when using Fe(III)EDTA− as extractant (5.81 × 10−7 m s−1) for sulfide extraction was one order of magnitude lower than with anaerobic water (2.54 × 10−6 m s−1). On the other hand, the sulfide removal efficiency with Fe(III)EDTA− was higher (84%) compared with anaerobic water (60%) as extractant. An additional mass transfer resistance was formed by elemental sulfur which remained attached to the membrane surface.CONCLUSIONS: Extraction of sulfide and VOCS from a synthetic wastewater solution through a silicone rubber membrane is a feasible process as alternative to the techniques developed to treat VOSC emissions. Optimizing the aqueous absorption liquid can increase the efficiency of extraction based processes. Copyright © 2008 Society of Chemical Industry

Removal of Cu (II), Ni (II) and Cr (III) Ions from Wastewater Using Complexation-Ultrafiltration Technique

In the recent years, the complexationultrafiltration technique has been shown to be a promising technique for removal of heavy metals in solution. In this study, a polymerenhanced ultrafiltration process has been investigated for removal of toxic heavy metals such as Cu(II), Ni(II), and Cr(III) from synthetic wastewater solutions. Carboxy methyl cellulose as a water-soluble polymer was used for complexing the cationic forms of the heavy metals before filtration. The functions of the metal-CMC complexation are to increase their molecular weight and their size. The size of the complex has to be larger than the pores of the selected membrane so the complex can be retained. Permeate water is then purified from the heavy metals. Filtration experiments were performed with ultrafiltration membrane system, equipped with a polyethersulfon membrane with a 10000 Daltons cut-off. The pressure was fixed at 1 bar with a permeate flow rate of 7.5 l/h. Different parameters, affecting the percentage rejection of the metals, such as pH and metal/CMC ratio have been investigated. Results obtained revealed that the maximum percentage of the metals rejection was achieved at pH ≥ 7 with increasing of the CMC concentration. Advantages of that technology over the other conventional technologies are the low energy requirements involved in ultrafiltration, the very fast reaction kinetics, and the high selectivity of separation.

Abatement of the Inhibitory Effect of Chloride Anions on the Photo-Fenton Process

The inhibition of the photo-Fenton (Fe2+/Fe3+, H2O2, UV light) degradation of synthetic phenol wastewater solutions by chloride ions is shown to affect primarily the photochemical step of the process, having only a slight effect on the thermal or Fenton step. Kinetic studies of the reactions of oxoiron (IV) (FeO2+) with phenol indicate that, if FeO2+ is formed in the photo-Fenton degradation, its role is probably minor. Finally, it is shown that, for both a synthetic phenol wastewater and an aqueous extract of Brazilian gasoline, the inhibition of the photo-Fenton degradation of the organic material in the presence of chloride ion can be circumvented by maintaining the pH of the medium at or slightly above 3 throughout the process, even in the presence of significant amounts of added chloride ion (0.5 M).