Color Removal Research Articles

Photo-alternating current-electrocoagulation technique: Studies on operating parameters for treatment of industrial wastewater

In this investigation, several electrochemical and advanced oxidation processes (AOPs), including photolysis (UV), direct/alternating current-electrocoagulation (DC/AC/EleC), and photo-direct/alternating current-electrocoagulation (UV/DC/AC/EleC) process were examined regarding their capacity in order to reduce the amount of chemical oxygen demand (COD) and color in distillery industrial wastewater (DIW), as well as the effect these factors have on the amount of electricity required to treat the wastewater. Experimental results showed that compared to single UV, DC/EleC, AC/EleC, and hybrid UV/DC/EleC processes, the hybrid UV/AC/EleC process provided excellent color-100 % and COD-100 % removal efficiencies with a lowered usage of energy of 8.54 kWhr m−3. The influence of critical operational variables such as treatment time (30–240 min), photo (8–40 W), pulse duty cycle (0.14–0.86), current (0.15–0.90 Amp), pH (1.50–11.50), chemical oxygen demand (3000–9000 mgL−1), inter electrode spacing (1–4 cm), electrode combination (Fe/Fe, Fe/Al,Al/Fe, Al/Al), and electrolyte concentration (1–5 g L−1) on the efficiency of% color and COD removal, as well as the energy utilization of DIW were examined applying a hybrid UV/AC/EleC method. The synergistic index between UV and the AC/EleC process was also examined and discussed in this work. The UV/AC/EleC technique is the most advantageous choice in comparison to the other approaches since it can be applied to properly and efficiently remove pollutants from wastewater and industrial effluent.

Treatment of mature landfill leachate using chemical and electrical Fenton with novel Fe-loaded GAC heterogeneous catalysts

In this study, heterogeneous Fenton catalysts were prepared by loading iron oxides on granular activated carbon (GAC), with which as heterogeneous Fenton catalysts, mature landfill leachate (MLL) was treated by chemical and electrical Fenton method. For chemical Fenton treatment of MIL, the optimum conditions were optimised by orthogonal experiments and the removal of COD, NH3-N and colour reached 93.7 %, 65.5 % and 84 % respectively for static experiments, whereas the heterogeneous Fenton fluidized bed reactor removed >90 % of COD in all the 12 h of continuous operation. For electrical Fenton treatment of MIL, the removal rates of COD, colour, NH3-N, and TN were 97.4 %, 99 %, 100 %, and 94.2 %, respectively under the optimum treatment conditions of pH = 5, the GAC/α-FeOOH catalyst dosage of 13.3 g L−1, and the applied voltage of 8 V with the energy consumption of only 0.23 kWh (g COD)−1. Upon characterization, humic acid, fulvic acid and xanthohumic acid in the MLL were completely degraded and the complex macromolecules such as polycyclic aromatic hydrocarbons and heterocyclic rings were reduced and converted to simple small molecules such as alkanes. The quenching experiments verified that the ·OH produced in the heterogeneous electrical Fenton system plays an important role in the degradation of MLL, while the removal of NH3-N also relies on indirect oxidation with the active chlorine produced by the electrochemical system. GAC-based heterogeneous Fenton catalysts with high catalytic capacity and easy recycling have good application prospects in treating MLL.

Ensemble machine learning as a mathematical approach to predict high-voltage electric field-assisted removal of color and oxidative indices from soybean oil using the activated porous electrodes

Porous electrode materials provide a large surface area for electrochemical reactions and facilitate ion transport efficiently. By optimizing the design and properties of porous electrodes, it is possible to enhance the bleaching performance. In this research, three machine learning (ML) algorithms, namely Support Vector Regression, Ridge Regression, and Decision Tree Regression were utilized for predicting the bleaching efficiency under different conditions of HVEF-assisted bleaching (HVEFAB). Subsequently, the outcomes of these models were compared to ensemble models created by combining the algorithms as mentioned earlier using three techniques including bagging, boosting, and stacking. The levels of chlorophyll and carotenoids were reduced as a result of increased voltage, modification in the electrode surface, number of cathode-anode, and the presence of an inert electrolyte. Meanwhile, the reduction of red color and chlorophyll pigments was more significant than yellow color and carotenoid pigments. Moreover, the application of HVEFAB can potentially decrease the levels of polar compounds, such as oxidative compounds on the electrode surface. Based on the MSE, MAE, and R2 metrics, the algorithms' efficacy in forecasting outputs 1 (color index) and 2 (oxidative index) can be ordered as follows: Stacking > Boosting > Bagging > Decision Tree (DT) > Ridge > Support Vector Regression (SVR). The findings demonstrate that integrating these three models, mainly through the stacking technique, substantially improves the accuracy of the predicting model. Particle swarm optimization (PSO) and polynomial regression rather than RSM represented a superior model to predict red color removal.

Coagulation process for the removal of color and turbidity from wet coffee processing industry wastewater using bio-coagulant: Optimization through central composite design

The growing problem of industrial pollution in developing countries, especially Ethiopia, has sparked serious issues about the quality of the water, particularly when it comes to the effluent from wet coffee processing industries. In response, this study investigates the potential of utilizing natural coagulants, Acanthus sennii C., Moringa stenopetala B., and Aloe vera L., either individually or in combination, for the treatment of coffee effluent. Methodologically, the study systematically varies operational parameters, including coagulant dose, pH levels, stirring speed, and stirring time, to evaluate their impact on coagulation efficiency. Experimental data undergo statistical analysis, employing ANOVA, while computational optimization techniques are employed using Design Expert software to determine optimal conditions. Notably, the blended form of the three coagulants emerges as particularly promising, yielding optimal conditions of 0.750 g/L coagulant dosage, pH 8.76, agitation speed of 80.73 rpm, and agitation time of 19.23 min. Under these optimized conditions, the blended coagulant achieves remarkable removal efficiencies, approximately 99.99% for color and 98.7% for turbidity. These findings underscore the efficiency of natural coagulants, particularly in blended form, for sustainable wastewater treatment in wet coffee processing.

Fabrication of MoS2 restrained magnetic chitosan polysaccharide composite for the photocatalytic degradation of organic dyes

Chitosan (CS) polysaccharide is expected to exhibit greater ionic conductivity, which can be attributed to its increased amino group content when it is blended with different semiconducting materials. Herein, the work used this conducting ability of chitosan and prepared a heterogeneous MoS2-induced magnetic chitosan (MF@CS) composite via the co-precipitation method, which was used to scrutinize the catalytic performance with Methylene Blue (MB) and Malachite Green (MG) dyes by visible light irradiation. The saturation magnetization value of the MF@CS composite is found to be 7.8 emu/g, which is less when compared to that of pristine Fe3O4 (55.7 emu/g) particles. The bandgap of the MF@CS composite is ∼ 2.17eV, which exceeds the bandgap (Eg) of bare MoS2 of 1.80 eV. The maximum color removal of 96.3 % and 93.4 % for MB and MG dyestuffs is recognized in the exposure of the visible spectrum, respectively. At a starting dye dosage of 30 mg/L, 0.1 g/L of MF@CS, a pH level of 8−11, and 70 min of contact with direct light. The photocatalyst provides extremely good durability for a maximum of five phases. Hence, the MF@CS matrix is a viable and appropriate substance for the efficient treatment of effluents containing dye molecules.

Synthesis and application of natural asphalt sulfonic acid (NA-SO3H) as a novel and reusable carbonaceous super adsorbent for rapid decolorization of aqueous dye solutions

This research involves functionalizing solid natural asphalt through sulfonation in the presence of H2SO4. The resulting product, known as mildly sulfonated natural asphalt sulfonic acid (ms-NA-SO3H), was investigated and confirmed by SEM, DRS, EDX, BET, CHNOS, and FT-IR analyses. The FT-IR spectrum of ms-NA-SO3H displays distinctive absorption peaks related to the presence of asymmetric and symmetric stretching modes of SO2, which are associated with SO vibrations. These findings confirm the successful sulfonation of natural asphalt. The SEM images illustrated that the surface of natural asphalt appears relatively smooth, with minimal porosity except for occasional cracks. Conversely, the external surface of the ms-NA-SO3H adsorbent exhibits irregular pores, compared to natural asphalt. In the next step, the porous heterogeneous bituminous has been used for the decolorization of methylene blue, and methyl orange solutions. Variation of removal percent versus dye concentration showed functionalization surface groups of natural asphalt with SO3H groups have provided high activated sites for color removal from the aqueous environment. Various parameters such as solution pH, contact time, adsorbent dosage, and initial dye concentration, were examined. The results of surface adsorption analysis at different concentrations revealed that the adsorption behavior on the adsorbent could be accurately described by the Langmuir isotherm and the pseudo-second-order kinetic model. The rapid removal and high adsorption capacity of the modified asphalt indicate its efficiency in the surface adsorption processes. The reusability of the ms-NA-SO3H adsorbent was studied via a physical adsorption mechanism, using ethanol or dimethyl formamide. Obtained results showed the prepared modified asphalt is a simple, efficient, cost-effective, and environmentally friendly candidate for different pollution removal.

Advancement in Sustainable Wastewater Treatment: A Multifaceted Approach to Textile Dye Removal through Physical, Biological and Chemical Techniques

AbstractThe global manufacturing sector heavily relies on the textile industry, yet the widespread utilization of synthetic dyes within this sector has raised serious environmental apprehensions, notably regarding wastewater contamination. The release of untreated wastewater containing residual dyes poses a significant risk to both aquatic ecosystems and human well‐being. In reaction to this issue, considerable efforts have been made to develop efficient and sustainable methods for the removal of textile dyes from wastewater. This comprehensive review paper furnishes in‐depth literature information covering various aspects of dyes, including their classification, toxicity effects, and evaluation of recent advancements in dye removal technology, emphasizing their advantages, limitations, and future potential. Various strategies are covered, including physical, chemical, and biological methods. Physical techniques like adsorption, filtration, and membrane technologies are contrasted with chemical approaches such as coagulation, precipitation, and advanced oxidation processes. Biological methods include the utilization of micro‐organisms, fungi, and enzymes to break down or metabolize dye compounds. Key considerations in the critical analysis include the efficiency, cost‐effectiveness, and scalability of each method. This review focuses on enzyme breakdown (biological) and adsorption (physical) color removal procedures, which are currently considered the most effective. It also proposes the utilization of a composite adsorbent, anticipating enhanced efficiency and faster removal of dyes through this technique.

Treatment of tomato paste wastewater by electrochemical and membrane processes: process optimization and cost calculation.

This study investigated the treatment of wastewater from tomato paste (TP) production using electrocoagulation (EC) and electrooxidation (EO). The effectiveness of water recovery from the pretreated water was then investigated using the membrane process. For this purpose, the effects of independent control variables, including electrode type (aluminum, iron, graphite, and stainless steel), current density (25-75 A/m2), and electrolysis time (15-120 min) on chemical oxygen demand (COD) and color removal were investigated. The results showed that 81.0% of COD and 100% of the color removal were achieved by EC at a current density of 75 A/m2, a pH of 6.84 and a reaction time of 120 min aluminum electrodes. In comparison, EO with graphite electrodes achieved 55.6% of COD and 100% of the color removal under similar conditions. The operating cost was calculated to be in the range of $0.56-30.62/m3. Overall, the results indicate that EO with graphite electrodes is a promising pretreatment process for the removal of various organics. In the membrane process, NP030, NP010, and NF90 membranes were used at a volume of 250 mL and 5 bar. A significant COD removal rate of 94% was achieved with the membrane. The combination of EC and the membrane process demonstrated the feasibility of water recovery from TP wastewater.

Sonochemical synthesis of SnS and SnS2 quantum dots from aqueous solutions, and their photo- and sonocatalytic activity

Our study reports the ultrasound-assisted synthesis of SnS and SnS2 in the form of nanoparticles using aqueous solutions of respective tin chloride and thioacetamide varying sonication time. The presence of both compounds is confirmed by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, as well as Raman and FT-IR spectroscopic techniques. The existence of nanoparticles is proven by powder X-ray diffraction investigation and by high resolution transmission electron microscopy observations. The size of nanocrystallites are in the range of 3–8 nm and 30 50 nm for SnS, and 1.5–10 nm for SnS2. X-ray photoelectron spectroscopy measurements, used to investigate the chemical state of tin and sulphur atoms on the surface of nanoparticles, reveal that they are typically covered with tin on the same oxidation degree as respective bulk compound. Values of optical bandgaps of synthesized nanoparticles, according to the Tauc method, were 2.31, 1.47 and 1.05 eV for SnS (60, 90 and 120 min long synthesis, respectively), and 2.81, 2.78 and 2.70 eV for SnS2 (60, 90 and 120 min long synthesis, respectively). Obtained nanoparticles were utilized as photo- and sonocatalysts in the process of degradation of model azo-dye molecules by UV-C light or ultrasound. Quantum dots of SnS2 obtained under sonication lasting 120 min were the best photocatalyst (66.9 % color removal), while quantum dots of SnS obtained under similar sonication time were the best sonocatalyst (85.2 % color removal).

Actas Pink-2B dye removal in biochar nanocomposites augmented vertical flow constructed wetland (VF-CWs)

Industries generate hazardous dye wastewater, posing significant threats to public health and the environment. Removing dyes before discharge is crucial. The ongoing study primarily focused on synthesizing, applying, and understanding the mechanism of green nano-biochar composites. These composites, including zinc oxide/biochar, copper oxide/biochar, magnesium oxide/biochar, and manganese oxide/biochar, are designed to effectively remove Actas Pink-2B (Direct Red-31) in conjunction with constructed wetlands. Constructed wetland maintained pH 6.0–7.9. At the 10th week, the copper oxide/biochar treatment demonstrated the highest removal efficiency of total suspended solids (72%), dissolved oxygen (7.2 mg/L), and total dissolved solids (79.90%), followed by other biochar composites. The maximum removal efficiency for chemical oxygen demand (COD) and color was observed at a retention time of 60 days. The electrical conductivity also followed the same order, with a decrease observed up to the 8th week before becoming constant. A comprehensive statistical analysis was conducted, encompassing various techniques including variance analysis, regression analysis, correlation analysis, and principal component analysis. The rate of color and COD removal followed a second-order and first-order kinetics, respectively. A significant negative relationship was observed between dissolved oxygen and COD. The study indicates that employing biochar composites in constructed wetlands improves textile dye removal efficiency.

The Use of Coagulation–Flocculation for Industrial Colored Wastewater Treatment—(I) The Application of Hybrid Materials

Polluting species released in industrial-colored effluents contaminate water, degrading its quality and persisting in the aquatic environment; therefore, it must be treated for safe discharge or onsite reuse/recycling to ensure a fresh water supply. This review has the principal goal of facilitating understanding of some important issues concerning wastewater (WW) treatment systems, mainly based on a coagulation–flocculation step, as follows: (i) the significance of and facilities offered by specialized treatment processes, including the coagulation–flocculation step as a single or associated step (i.e., coagulation–flocculation followed by sedimentation/filtration or air flotation); (ii) the characteristics of industrial-colored WW, especially WW from the textile industry, which can be reduced via the coagulation–flocculation step; (iii) primary and secondary groups of hybrid materials and their characteristics when used as coagulants–flocculants; (iv) the influence of different process operating variables and treatment regimens on the efficiency of the studied treatment step; and (v) the benefits of using hybrid materials in colored WW treatment processes and its future development perspectives. The consulted scientific reports underline the benefits of applying hybrid materials as coagulants–flocculants in colored textile WW treatment, mainly fresh, natural hybrid materials that can achieve high removal rates, e.g., dye and color removal of >80%, heavy metals, COD and BOD of >50%, or turbidity removal of >90%. All of the reported data underline the feasibility of using these materials for the removal of colored polluting species (especially dyes) from industrial effluents and the possibility of selecting the adequate one for a specific WW treatment system.

Multivariate optimization of organic matter and color removal from textile dyeing industry wastewater by ultraviolet-activated oxidants

This study investigated the efficiency of ultraviolet (UV) activation of the oxidants that are used in advanced oxidation processes in textile dyeing industry wastewater treatment with high concentrations of refractory organic matter and strong color. The effect of peroxymonosulfate (PMS), peroxydisulfate (PS), hydrogen peroxide (HP), percarbonate (PC), and chlorine as oxidants in UV-based processes was first evaluated. The two processes with the greatest removal efficiency were determined as UV/PS and UV/PMS. Then the operating parameters for UV/PS and UV/PMS were optimized by the Box-Behnken Design (BBD). Process parameters for both processes were oxidant dosage, initial pH, and reaction time whereas system responses were chemical oxygen demand (COD), UV254, and color removal efficiency. Under optimum conditions in the UV/PS process (pH 5.54, PS dosage 24.4 mM, and reaction time 117 min), COD, UV254, and color removal efficiency were 83.21 %, 92.14 %, and 93.87 %, respectively. Under optimum conditions in the UV/PMS process (pH 5.83, PMS dosage 23.1 mM, and reaction time 120 min), COD, UV254, and color removal efficiency were 66.89 %, 78.45 %, and 96.89 %, respectively. The R2 of all the models that applied for the system responses of both processes was nearly one and the adj R2 values were very near to the R2 values. These findings showed that the BBD is efficient, suitable, and significant in modeling the removal of pollutants in textile dyeing industry wastewater by UV/PS and UV/PMS processes. Electrical Energy per Order (EE/O) calculations for UV/PS and UV/PMS processes were 101 and 167 kWh/m3 for optimum conditions, respectively. The results showed that both UV/PS and UV/PMS processes are effective; however, the UV/PS process is more economical and effective concerning pollutant removal efficiency and EE/O calculations.

REMOVAL OF DIRECT BLUE DYE IN TEXTILEWASTEWATER EFFLUENT BY ELECTROCOAGULATION

Removal of direct blue dye by electrocoagulation method has been investigated using aluminum electrode in a bench-scale electrochemical system. Current density, NaCl concentration, electrocoagulation time, and dye concentration has been studied as effecting parameters in color removal efficiency. Increasing of current density will increase the color removal efficiency and energy consumption as well. While increasing NaCl concentration increase the color removal efficiency but it decrease energy consumption. High dye concentration is needed for extra electrocaogolation time to reach the same efficiency that obtained with low dye concentration .With current applied 0.35 amps. and NaCl concentration of 2 g/l more than 93% efficiency achieved in 14 min. of electrocaogolation time.

THE EFFECT OF IMMOBILIZED ENZYME ON TEXTILE WASTEWATER

Textile wastewater has a complex composition characterized by high dye content and chemical oxygen demand. Therefore, textile wastewaters have serious environmental impacts, such as aesthetic degradation, and carcinogenic properties. Treatment and the recovery of textile wastewater are important due to their high volume and toxicity. The effects of peroxidase enzyme immobilized on magnetic chitosan-clay beads of synthetic textile wastewater were investigated in a batch reactor. System performance was determined by chemical oxygen demand (COD) and color. The batch reactor was operated in three different pH (5, 7, 10), temperatures (25, 35, 45 °C), and reaction times (0-5-10-20-30 min.) with synthetic textile wastewater. As a result, COD and color removal efficiencies were determined as 44% and 56%, respectively, corresponding effluent concentrations are 1442 mg/L, 450 Pt-Co. The results of this study show that using the enzyme immobilization process is an effective method to remove color and COD concentration from textile wastewater.

Selection of White-Rot Fungi for Decolorization of Palm Oil Mill Effluent and Evaluation of Biodegradation and Biosorption Processes

Ten species of white-rot fungi were evaluated for their ability to decolorization of palm oil mill effluent. The highest decolorization efficiency was found with Trametes elegans (PP17-06), followed by Ganoderma sp.2 (PW17-06) and Ganoderma sp.2 (PW17-177), respectively. T. elegans was further evaluated for the long-term performance of decolorization for 24 d. The optimal retention time for the decolorization was 8 d, with a color removal efficiency of 47.7%. Beyond 18 d of incubation, decolorization efficiency was reduced due to the autolysis of enzymes. During the biodegradation process, manganese peroxidase enzyme activities reached a maximum of 36.03 U.L−1. However, no significant laccase and lignin peroxidase activities were observed. T. elegans was also assessed for decolorization performance through biosorption on mycelial biomass. The synthesis of the enzyme was prevented by exposing the mycelium to HgCl2. Within an optimal contact time of 2 d, decolorization efficiency reached 12.5% with ADMI reduction from 4259.0 (±20.1) ADMI to 3727 (±104.04) ADMI. Results indicate that the adsorption capacity was reached at this time, and no significant color removal can be achieved by biomass. Results obtained in this study showed the potential of T. elegans in decolorizing palm oil mill effluent.

Electrocoagulation (EC) treatment of model wastewater containing Rhodamine B

The colour removal of synthetic Rhodamine B (RhB) wastewater by using the electrocoagulation (EC) process in batch mode utilizing commercially available iron plates as electrodes was investigated. The colour removal (%) was calculated for the EC process by taking into account the effects of several factors such as pHi, current density, RhB concentration and temperature. When NaCl was utilized as the electrolyte for EC, the efficiency of colour removal was enhanced. At the optimal experimental conditions (pHi 7.0, 100 A/m2, 50 ppm RhB concentration, 30 minutes, 30 oC and 0.075 M NaCl concentration), the colour removal (%) was 87.27 %. The negative values of ΔH° and ΔS° and ΔG° indicate that the adsorption process was spontaneous in nature and unfavorable at higher temperatures. The electrical energy consumption was assessed to be 2.44 KWh/m3. Characterization of the sludge was also carried out.

Experimental support for a sustainable treatment strategy of acrylic fiber dyeing wastewater

AbstractThe study intended to devise a sustainable treatment scheme for acrylic fiber dyeing process effluents, which significantly differ from other textile plant wastewaters. The necessary experimental support was generated from a set of tests conducted on the wastewater of a plant operation, focused solely on acrylic fiber dyeing. Related experiments involved effluent characterization, biological treatability, and chemical settling/oxidation performed on raw and bio‐treated effluent, as pre‐treatment and/or polishing steps. A total COD level of 910 mg/L with a 70% soluble ratio, low total N and P contents below 10 mg/L, a detergent content of 50 mg/L and a dark/black color of 1150 Pt‐Co unit defined the average properties of the raw plant effluent. Experimental support indicated that activated sludge operation at a sludge age level above 25 d, remained insufficient as it could only provide an effluent with a soluble COD level above 150 mg/L, a biomass escape in the range of 40 to 100 mg/L and with an intense dark color. A similar experimental template, including chemical settling, chemical oxidation by NaOCl and combination of the two processes, was tested as pre‐treatment and a polishing step after biological treatment. Pre‐treatment, although with some benefit to remove toxic and inhibitory compounds, proved to be highly costly, due to excessive chemical usage and sludge generation for a sustainable, cost‐effective approach. The sequence of chemical oxidation and settling steps implemented as a polishing stage was quite effective as it secured complete color removal, a major source of concern for the selected wastewater and also, it reduced COD down to 60 mg/L, a level significantly below the residual COD threshold for biological treatment. This approach, although case‐specific for this study, provided a scientific and general perspective for similar work.

Treatment of membrane-concentrated landfill leachate by heterogeneous chemical and electrical Fenton processes with Iron-loaded granular activated carbon catalysts

The composition of the membrane-concentrated landfill leachate (MCLL) is complex with a high concentration of organic matter and inorganic ions. In this study, a chemical and an electro-Fenton system were constructed to treat MCLL from a mature landfill using granular activated carbon loaded with iron oxides as heterogeneous Fenton catalysts. In the chemical Fenton treatment optimized by orthogonal experiments, the COD and colour removal rates were 93.9% and 80.2%. For the electro-Fenton system, the best COD, colour, and TN removal rates of MCLL reached 95.7%, 99%, and 94.9% with an energy consumption (EC) of 0.098 kWh·(g COD)−1 under the condition of pH 6, applied voltage 8 V, the reaction time 4 h, and the catalyst dosage 16.67 g L−1. Various spectral analyses confirmed that refractory organic matter and toxic substances in the MCLL were effectively degraded. The synergistic effect study of the factors in chemical Fenton indicated that as far as the effect on COD removal is concerned, heterogeneous Fenton system > catalyst adsorption > activated carbon/H2O2 system > activated carbon adsorption. The results of free radical quenching experiments illustrate that a large amount of ·OH was produced in the chemical heterogeneous Fenton system, while both ·OH and active chlorine play important roles in the removal of pollutants for the electro-Fenton system. MCLL can be disposed of costly and effectively by chemical and electrical Fenton processes with Iron-loaded granular activated carbon catalysts.

An Optimal Culture Medium for Laccase Production and Sugar Cane Vinasse Biotreatment with Trametes villosa Using Plackett-Burman and Central Composite Designs

The optimal conditions for laccase production and vinasse biotreatment with a native strain of Trametes villosa were determined by a screening-optimization approach. Eleven factors including nutrient concentration, vinasse dilution (%v/v), inoculum volume, carbon to nitrogen ratio and initial pH, were investigated for their effects on laccase activity applying the Plackett-Burman screening design. The selected factors were optimized using a central composite design, and then evaluated on a vinasse biotreatment experiment. The factors that contributed the most to the enzymatic activity were the concentrations of MgSO4∙7H2O (A), FeSO4∙7H2O (B) and CuSO4∙5H2O (C), alongside initial pH. After 10 days, laccase activity was 544.038 U L-1 for the following concentrations of A, B and C: 0.250 g L-1, 0.020 mg L-1, and 0.100 g L-1, respectively. Vinasse biotreatment under optimized conditions resulted in 82.74%, 78% and 75.97% of phenol, color, and COD removal respectively, while final pH value was 6.90. These results showed that the native strain of T. villosa has a good potential for further research on laccase production and vinasse sustainable management.

Preparation of La-doped Ti/SnO2-Sb2O4 anode and its electrochemical oxidation performance of rhodamine B.

In this paper, La-doped Ti/SnO2-Sb2O4 electrode was prepared by electrodeposition and used for electrochemical degradation of rhodamine B. The optimum preparation conditions of the electrode were optimized as deposition time of 15min and calcination at 500 ℃ for 2h. The water treatment conditions were selected as initial pH 3.0, electrolyte Na2SO4 concentration 0.1M, current density 30mAcm-2, and initial rhodamine B concentration 20mg L-1; the color and TOC removal of RhB reached 99.78% and 82.41% within 30min. The FESEM, XRD, XPS, CV, LSV, and EIS characterization studies demonstrated that Ti/SnO2-Sb2O4-1%La electrode had a dense structure and the highest oxygen evolution potential (2.14V) and lowest charge transfer resistance (0.198 Ω cm-2), indicating that doped La has lower energy consumption. Moreover, La doping can expand the specific surface area, active site, performance of pollutant degradation, and service life of the electrode. Especially, the service life of Ti/SnO2-Sb2O4-1%La is increased by three times, and the maximum life span reaches 90min (1000mAcm-2, 1M H2SO4). Free radical quenching experiments show that ·OH plays a major role in the degradation of RhB. The Ti/SnO2-Sb2O4-1%La electrode prepared in this paper and its results will provide data support and reference for the design of efficient electrocatalytic electrode.