Electrocoagulation of blue reactive, red disperse and mixed dyes, and application in treating textile effluent

Electromagnetic field-enhanced novel tubular electrocoagulation cell for effective and low-cost color removal of beet sugar industry wastewater

The treatment of real beet sugar mill effluent by a modified electrocoagulation process is proposed. An innovative design of an electromagnetic field-enhanced electrochemical cell consisting of a tubular screen roll anode and two cathodes (an inner and outer cathode) has been used. Different parameters have been investigated including current density, effluent concentration, NaCl concentration, rpm, number of screen layers per anode, and the effect of addition and direction of an electromagnetic field. The results showed that, under the optimum conditions, current density of 3.13 A/m², two screens per anode, NaCl concentration of 12 g/l, and rotation speed of 120 rpm, the percentage of color removal was 85.5% and the electrical energy consumption was 3.595 kWh/m³. However, the presence of an electromagnetic field distinctly enhanced the energy consumption and the color removal percentage. Numerically, applying the magnetic field resulted in performing a color removal efficiency of 97.7% using a power consumption of 2.569 KWh/m³ which is considered a distinct achievement in industrial wastewater treatment process. The strong enhancement in color removal using a low power consumption significantly reduced the required treatment cost; the estimated treatment cost was 0.00017 $/h.m². This design has proven to be a promising one for the continuous treatment of beet sugar industrial effluents and to be a competitor to the currently available techniques.

Efficient removal of tannins from anaerobically-treated palm oil mill effluent using protein-tannin complexation in conjunction with electrocoagulation

Despite the significant removal of chemical oxygen demand (COD) by anaerobic digestion, anaerobically-treated palm oil mill effluent (POME) still contains tannins and other phenolic compounds, resulting in residual COD and a brownish color. In this study, we investigated the removal of tannins from anaerobically treated POME using protein-tannin complexation in conjunction with electrocoagulation. The amino acid composition of the protein, aqueous pH, and protein: tannin ratios were found to be important parameters affecting the tannin removal efficiency. Pig blood protein was superior to casein protein in removing tannins, possibly because it had aspartic acid as the major amino acid component. At an optimal condition with a pig blood protein: tannin ratio of 0.33 (w/w), a current density of 30 mA/cm², pH 5, and an electrolysis time of 10 min, the removals of tannins, COD, and color were 93%, 96%, and 97%, respectively.

Role of Electrochemical Techniques for Photovoltaic and Supercapacitor Applications

Electrochemistry forms the base of large-scale production of various materials, encompassing numerous applications in metallurgical engineering, chemical engineering, electrical engineering, and material science. This field is important for energy harvesting applications, especially supercapacitors (SCs) and photovoltaic (PV) devices. This review examines various electrochemical techniques employed to fabricate and characterize PV devices and SCs. Fabricating these energy harvesting devices is carried out by electrochemical methods, including electroreduction, electrocoagulation, sol-gel process, hydrothermal growth, spray pyrolysis, template-assisted growth, and electrodeposition. The characterization techniques used are cyclic voltammetry, electrochemical impedance spectroscopy, photoelectrochemical characterization, galvanostatic charge-discharge, and I-V curve. A study on different recently reported materials is also presented to analyze their performance in various energy harvesting applications regarding their efficiency, fill factor, power density, and energy density. In addition, a comparative study of electrochemical fabrication techniques with others (including physical vapor deposition, mechanical milling, laser ablation, and centrifugal spinning) has been conducted. The various challenges of electrochemistry in PVs and SCs are also highlighted. This review also emphasizes the future perspectives of electrochemistry in energy harvesting applications.

Treatment of slaughterhouse wastewater by electrocoagulation and electroflotation as a combined process: process optimization through response surface methodology

The contamination of water with organic compounds has become an increasing concern in today's world. The cost-effective and sustainable treatment of industrial wastewaters is a major challenge. Advanced treatment techniques such as electrocoagulation-electroflotation offer economic and reliable solutions for the treatment of industrial wastewater. In this study, the electrocoagulation-electroflotation method was investigated for the simultaneous removal of chemical oxygen demand, total phosphorus, total Kjeldahl nitrogen, and color via response surface methodology. Factors such as electrode combination (Fe and Al), current density (10-20 mA/cm²), pH (3.0-9.0), and electrode distance (1-3 cm) were investigated in the treatment of wastewater to obtain maximum treatment efficiency. It was determined that chemical oxygen demand, total Kjeldahl nitrogen, total phosphorus, and color removal reached up to 94.0%, 77.5%, 97.0%, and 99.0%, respectively. Treatment costs were found as $0.71 with the Al-Fe electrode combination.

Enhancement of the electro-activated persulfate process in dye removal using graphene oxide nanoparticle

This study aimed to improve the speed of the electrochemical process by graphene oxide nanoparticle as a current accelerator in Acid Blue 25 removal from aqueous solutions. To do so, the effect of different parameters including pH, dye concentration, sodium persulfate concentration, the ratio of sodium persulfate to iron (II) sulfate concentration, current density, and the distance between electrodes was investigated on dye removal. Under optimal conditions of pH = 5, dye concentration = 200 mg/L, sodium persulfate concentration = 500 mg/L, iron (II) sulfate concentration = 100 mg/L, current density = 16.67 mA/cm², and electrode distance = 2 cm, 95% of dye was removed after 60 min in the electro-activated persulfate process; while the modified electro-activated persulfate process achieved 95% dye removal after only 40 min under the same conditions. This system was able to remove 90% of dye after 60 min at a higher concentration (300 mg/L). Also, the modified electro-activated persulfate process obtained the removal of 80% of COD, and 54% of TOC after 180 min in the mentioned conditions, for the dye concentration of 300 mg/L.

Phytoremediation potentials of Eichhornia crassipes for nutrients and organic pollutants from textile wastewater

We used live water hyacinth (WH, Eichornnia crassipes) to purify effluents from textile factories and monitored changes in the physicochemical properties, organic pollutants, and WH biomass. Although the water plant could not thrive in the highly polluted effluents after eight weeks, it achieved 55, 91, 53, 84, 96, 53, and 55% removal efficiency for total Kjeldahl-N (tK-N), NH₃-N, organic-N, PO₄^3-, SO₄^2-, Cl^-, and hardness, respectively. Likewise, the biomass growth showed a positive and strong correlation with NH₃-N (0.998), tK-N (0.956), organic-N (0.923), pH (0.853), and EC (0.712). In contrast, chemical oxygen demand and total oil and grease (TOG) evinced negative and strong correlations of -0.994 and -0.807, respectively. Further, Cl^- correlated mildly (-0.38), while alkalinity (0.154) and water hardness (-0.296) were less influential on the biomass growth. From the removal models, an average of 312 ± 7.7 g of WH would ensure 100% remediation of the nutrients in 29.2 ± 2.5 days. Except for organic-N, the removal kinetics generally favors pseudo-first-order, suggesting the sorbates' concentration and contact time as the limiting factors. Conclusively, WH is a phytoremediator of high potentials for industrial textile effluents, provided the effluents are conditioned at optimum concentration before contact with mature WH of sufficient biomass weight. Novelty statement Eichhornia crassipes was used for simultaneous removal of nutrients and organics from textile effluents. The influence of the macrophte's biomass weight and maturity on the remediation process were examined. Also, the limiting parameters that govern the remediation process were investigated via statistical correlation and kinetic study.

A Review of Current and Emerging Approaches for Water Pollution Monitoring

The aquatic ecosystem is continuously threatened by the infiltration and discharge of anthropogenic wastewaters. This issue requires the unending improvement of monitoring systems to become more comprehensive and specific to targeted pollutants. This review intended to elucidate the overall aspects explored by researchers in developing better water pollution monitoring tools in recent years. The discussion is encircled around three main elements that have been extensively used as the basis for the development of monitoring methods, namely the dissolved compounds, bacterial indicator, and nucleic acids. The latest technologies applied in wastewater and surface water mapped from these key players were reviewed and categorized into physicochemical and compound characterizations, biomonitoring, and molecular approaches in taxonomical and functional analyses. Overall, researchers are continuously rallying to enhance the detection of causal source for water pollution through either conventional or mostly advanced approaches focusing on spectrometry, high-throughput sequencing, and flow cytometry technology among others. From this review’s perspective, each pollution evaluation technology has its own advantages and it would be beneficial for several aspects of pollutants assessments to be combined and established as a complementary package for better aquatic environmental management in the long run.

Removing Disperse red 60 and Reactive blue 19 dyes removal by using Alcea rosea root mucilage as a natural coagulant

In terms of health, dyes have carcinogenic, mutagenic and toxic properties and can have adverse effects on health and the environment. Therefore, sewage containing to dyes must be purified before being discharged into the environment. The current study aimed to investigate the effectiveness of Alcea rosea root extract in Disperse red 60 and Reactive blue 19 dyes removal from synthetic sewage. In this study, the effect of different indices including pH (5–11), Alcea rosea concentration (50–300 mg/L) and initial dye concentration (10–80 mg/L) was investigated. During the tests, the coagulant was stirred with rapid mixing at a speed of 250 rpm for 2 min. In the following, the speed (30–60 rpm) and the time (10–25 min) were used for slow mixing and after mixing the effect of settling time (10–60 min) and temperature (20–70) on removal efficiency of Disperse and Reactive dyes was investigated. The results showed that the maximum of removal efficiency of Disperse and Reactive dyes in optimum conditions including (pH = 11, coagulant concentration = 200 and 250 mg/L, dye concentration 40 and 20 mg/L, speed 60 rpm, during 15 min with settling time 60 min and temperature 60 °C obtained 86% and 68%, respectively. According to the result, the Alcea rosea coagulant has the best ability in removing dyes from aqueous solutions and sewage, especially Disperse dyes. Disperse dye is much eliminated in the coagulation process due to its lower solubility, higher suspending materials and less required solved chemical oxygen demand to the total chemical oxygen demand (SCOD/TCOD).

ZnO/UV/H2O2 Based Advanced Oxidation of Disperse Red Dye

In view of promising efficiency of advanced oxidation process, ZnO/UV/H2O2 based advanced oxidation process (AOP) was employed for the degradation of Disperse Red-60 (DR-60) in aqueous medium. The process variables such as concentration of catalysts, reaction time, pH, dye initial concentration and H2O2 dose were evaluated for maximum degradation of dye. The maximum degradation of 97% was achieved at optimum conditions of H2O2 (0.9 mL/L), ZnO (0.6 g/L) at pH 9.0 in 60 min irradiation time. The analysis of treated dye solution revealed the complete degradation under the effect of ZnO/UV/H2O2 treatment. The water quality parameters were also studied of treated and un-treated dye solution and up to 79% COD and 60% BOD reductions were achieved when dye was treated with at optimum conditions. The dissolved oxygen increased up to 85.6% after UV/H2O2/ZnO treatment. The toxicity was also monitored using hemolytic and Ames tests and results revealed that toxicity (cytotoxicity and mutagenicity) was also reduced significantly. In view of promising efficiency of UV/H2O2/ZnO system, it could possibly be used for the treatment of wastewater containing toxic dyes.

Feasibility study of the use of basic oxygen furnace sludge in a permeable reactive barrier

In this study, the steel manufacturing waste Basic Oxygen Furnace Sludge (BOFS) was tested as permeable reactive material for the remediation of soil contaminated with chromium. The material presents a high content of elemental iron and iron oxides typical of the steel manufacturing process. Here we propose a scheme of the chemical reactions responsible for remediation process including BOFS dissolution, Cr(VI) reduction and Cr(III) precipitation. Batch reactors showed that Cr(VI) removal increases as the pH decreases. Column tests demonstrated that the simulated PRB with BOFS as the reactive media was quite effective for removing Cr(VI) from groundwater, with a sorption capability of 0.213 mg Cr per gram of BOFS at an initial Cr(VI) concentration of 50 mg L^-1 at pH 5.5. A long-term test lasting 71 days confirmed the proposed mechanisms and the suitability of using BOFS in a permeable reactive barrier.

Pulse electro-coagulation application in treating dibutyl phthalate wastewater

Pulse electro-coagulation (PEC) was applied to treat plastic factory wastewater in this study. One representative plasticizer molecule was chosen for the synthetic wastewater: dibutyl phthalate (DBP). Experiments demonstrated that PEC exhibits superior economic efficiency and removal efficiency compared to traditional electro-coagulation in wastewater treatment. Experimental data also indicated that at a given current density, compared with the aluminum electrode, the iron electrode could more efficiently remove DBP from wastewater. With an initial pH of 8-9, the required energy was 2.5 kWh m^-3 for 75% DBP removal in the case of iron as the anode type. In general, the pollutants have been successfully reduced to environmentally acceptable levels under the following operating conditions: iron as the anode type, interelectrode distance of 10 mm, duty cycle of 0.6, pH of 8-9 and current density of 15 mA cm^-2 for PEC time >15 min.

A review of electrocoagulation technology for the treatment of textile wastewater

The conventional coagulation technique of textile wastewater treatments is plagued with the issue of low removal rate of pollutants and generation of a large quantity of sludge. Recently, electrocoagulation (EC) technique gained immense attention due to its efficiency. The technique involves dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes and amasses particles and then removes them by precipitation or adsorption. EC process is influenced by operating parameters such as applied current density, electrodes material and configuration, type of electrical connection, pH and conductivity of the solution, and mixing state. Consequently, this work reviewed the major and minor reactions of EC process with operational parameters, design of EC cell, mass transfer studies and modeling, and industrial wastewater applications. The work also includes comparison of EC technique with conventional coagulation and combinations with other techniques. Special emphasis is on removal of pollutants from textile wastewater. Further, the electrical energy supplies and cost analysis are also discussed. Even though several publications have covered EC process recently, no review work has treated the systematic process design and how to minimize the effect of passivation layer deposited on the surface of the electrodes. EC process with rotating electrodes has been recommended to reduce this phenomenon. The effect of electrodes geometry is considered to enhance the conductivity of the cell and reduce energy consumption. The studies of ionic mass transfer were not implemented before special by limiting current method during the EC process. Moreover, no aforementioned studies used computational fluid dynamics modeling to present the mass transfer inside the EC reactor.

Adsorption of reactive blue BF-5G dye by soybean hulls: kinetics, equilibrium and influencing factors

The textile industry is known for the high use of chemicals, such as dyes, and large volumes of effluent that contaminate waters, a fact that has encouraged research and improved treatment techniques. In this study, we used unprocessed soybean hulls for the removal of reactive blue BF-5G dye. The point of zero charge of soybean hulls was 6.76. Regarding the speed of agitation in the adsorption process, the resistance to mass transfer that occurs in the boundary layer was eliminated at 100 rpm. Kinetics showed an experimental amount of dye adsorbed at equilibrium of 57.473 mg g(-1) obtained under the following conditions: dye initial concentration = 400 mg L(-1); diameter of particle = 0.725 mm; dosage = 6 g L(-1); pH 2; 100 rpm; temperature = 30 °C; and duration of 24 hours. The pseudo-second order best showed the dye removal kinetics. The adsorption isotherms performed at different temperatures (20, 30, 40 and 50 °C) showed little variation in the concentration range assessed, being properly adjusted by the Langmuir isotherm model. The maximum capacity of dye adsorption was 72.427 mg g(-1) at 30 °C. Since soybean hull is a low-cost industrial byproduct, it proved to be a potential adsorbent for the removal of the textile dye assessed.

Photocatalytic Membrane Reactor for the Removal of C.I. Disperse Red 73

After the dyeing process, part of the dyes used to color textile materials are not fixed into the substrate and are discharged into wastewater as residual dyes. In this study, a heterogeneous photocatalytic process combined with microfiltration has been investigated for the removal of C.I. Disperse Red 73 from synthetic textile effluents. The titanium dioxide (TiO₂) Aeroxide P25 was selected as photocatalyst. The photocatalytic treatment achieved between 60% and 90% of dye degradation and up to 98% chemical oxygen demand (COD) removal. The influence of different parameters on photocatalytic degradation was studied: pH, initial photocatalyst loading, and dye concentration. The best conditions for dye degradation were pH 4, an initial dye concentration of 50 mg·L⁻¹, and a TiO₂ loading of 2 g·L⁻¹. The photocatalytic membrane treatment provided a high quality permeate, which can be reused.

Biodegradability and toxicity assessment of a real textile wastewater effluent treated by an optimized electrocoagulation process

In this work, the application of an iron electrode-based electrocoagulation (EC) process on the treatment of a real textile wastewater (RTW) was investigated. In order to perform an efficient integration of the EC process with a biological oxidation one, an enhancement in the biodegradability and low toxicity of final compounds was sought. Optimal values of EC reactor operation parameters (pH, current density and electrolysis time) were achieved by applying a full factorial 3(3) experimental design. Biodegradability and toxicity assays were performed on treated RTW samples obtained at the optimal values of: pH of the solution (7.0), current density (142.9 A m(-2)) and different electrolysis times. As response variables for the biodegradability and toxicity assessment, the Zahn-Wellens test (Dt), the ratio values of dissolved organic carbon (DOC) relative to low-molecular-weight carboxylates anions (LMCA) and lethal concentration 50 (LC50) were used. According to the Dt, the DOC/LMCA ratio and LC50, an electrolysis time of 15 min along with the optimal values of pH and current density were suggested as suitable for a next stage of treatment based on a biological oxidation process.

Modeling and evaluation of electro-oxidation of dye wastewater using artificial neural networks

Treatment of CBSOL LE red wool dye containing wastewater by an electro-oxidation (EO) method was investigated using a Ti/RuO₂ electrode.

Adsorption of an azo dye in an aqueous solution using hydroxyl-terminated polybutadiene (HTPB)

This paper reports an investigation into the effect of a number of operating factors on the removal of Acid Blue 92 (AB92) from an aqueous solution using hydroxyl-terminated polybutadiene (HTPB) as an adsorbent. The optimum values of adsorbent dose and pH were found to be 35mgL(-1) and 6, respectively. Temperature showed a significant effect, with maximum dye removal being observed at 45°C. Stirring the solution during the treatment process resulted in significant removal improvement. The Langmuir adsorption model was used to quantify the amount of AB92 adsorbed on the surface of HTPB. FT-IR spectrometry results for HTPB, AB92, and HTPB-AB92 verified the efficiency of the treatment. Further, the adsorbent was characterized using SEM and H NMR techniques.

A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters

Textile industry is one of the most chemically intensive industries on the earth and the major polluter of potable water. It generates huge quantities of complex chemical substances as a part of unused materials including dyes in the form of wastewater during various stages of textile processing. The direct discharge of this wastewater into environment affects its ecological status by causing various undesirable changes. As environmental protection becomes a global concern, industries are finding novel solutions for developing technologies that can diminish the environmental damage. However, colour removal from textile wastewater by means of cheaper and environmental friendly technologies is still a major challenge. In this manuscript, several options of decolourisation of textile wastewater by chemical means have been reviewed. Based on the present review, some novel pre-hydrolysed coagulants such as Polyaluminium chloride (PACl), Polyaluminium ferric chloride (PAFCl), Polyferrous sulphate (PFS) and Polyferric chloride (PFCl) have been found to be more effective and suggested for decolourisation of the textile wastewater. Moreover, use of natural coagulants for textile wastewater treatment has also been emphasised and encouraged as the viable alternative because of their eco-friendly nature.

Electrocoagulation treatment of simulated floor-wash containing Reactive Black 5 using iron sacrificial anode

Floor-wash from dye finishing plant is a major source of color and wastewater volume for dyes industries. Batch electrocoagulation (EC) of simulated floor-wash containing Reactive Black 5 (RB5) was studied as a possible pretreatment option. More than 90% of initial 25mg/L of RB5 was removed at current densities of 4.5, 6, and 7.5 mA/cm(2) in the presence of Na(2)SO(4) and NaCl as supporting electrolytes; in less than one hour. Identical k(obs) (pseudo first-order reaction rate constant) values were obtained at initial pH of 3.74 for both electrolytes. However, at initial pH of 6.6, k(obs) values decreased in the presence of Na(2)SO(4) and remained same for NaCl as compared to that at pH 3.74. Highest extent of decolorization and k(obs) values were obtained at initial pH 9.0 for both electrolytes. Under identical conditions, specific energy consumption (SEC) was almost half in the presence of NaCl (~29 kWh/kg RB5) than that of Na(2)SO(4). Vinyl sulfone (VS) was detected as one of the products of EC indicating reduction of azo bonds as a preliminary step of decolorization. Mechanism of decolorization with respect to various experimental conditions was delineated. Generation and accumulation of VS was dependent on initial pH and type of electrolyte. Results of this study revealed that EC in the presence of sodium chloride can be efficiently used as a primary treatment for decolorization of floor-wash containing RB5.