Color Removal Efficiency Research Articles

Cu/TiO2 composite nanofibers with improved photocatalytic performance under UV and UV–visible light irradiation

This is the first-time report on the optimization of pure TiO2 and Cu/TiO2 nanocomposite photocatalytic fibrous materials fabricated by electrospinning followed by removal of the organic components by calcination at high temperature. Morphological investigations of the fabricated nanocomposites performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were supported with spectroscopic investigations via X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, ultraviolet–visible spectroscopy (UV–Vis) and photoluminescence (PL) spectroscopy. These findings clearly indicate that the copper presence into TiO2 lattice triggers the sunlight-driven photocatalysis, as compared to pure TiO2 that use the ultraviolet light to achieve the photoactivation. As a result, remarkable photocatalytic activity on the degradation of Amaranth dye was obtained. The maximum color removal efficiency of 99.84% was observed for the degradation of Amaranth dye for an initial concentration of 25 mg/L, after 240 min of Vis-light irradiation. Excellent results were obtained for the case of 0.05%Cu/TiO2 nanocomposite (calcinated at 400 °C) that yielded to a maximum value for the constant rate (k = 2.089 × 10−2 min−1). As compared to the undoped material (TiO2/400 °C), the 0.05%Cu/TiO2 nanocomposite led an almost double reaction rate (the constant rate increasing from 1.015 × 10−2 to 2.089 × 10−2 min−1). In addition, the 0.05%Cu/TiO2 nanocomposite calcinated at 400 °C was tested for the degradation of Amaranth dye under visible-light irradiation. Thus, at catalyst doses of 0.4 to 0.8 g/L, the reaction rate constant attained the order of 10−2 min−1 under visible irradiation. These results are outstanding when compared with previously reported works.

Pure and cerium-doped ZnO nanorods grown on reticulated Al2O3 substrate for photocatalytic degradation of Acid Red 88 azo dye

Pure and Ce-doped ZnO photocatalyst nanorods were both grown on α-Al2O3 ceramic foams manufactured using a polymeric sponge replication technique. A three-dimensional network of α- Al2O3 struts which served as the substrate for the photocatalyst material was first seeded via dip coating. The seed-mediated synthesis of ZnO nanorods with controlled lengths and diameters was then carried out at low temperature (∼95 °C) by chemical bath deposition (CBD). Their morphologies and crystallographic orientations were verified using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The effect of Ce-doping on the optical properties of the ZnO nanorods was investigated by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopies. There was a modification in the band-gap structure with the incorporation of cerium atoms in the ZnO matrix as observed by the partial redshift at the absorption edges and by the blue and green light emissions. Color removal efficiencies of the samples were evaluated under UVA and visible light irradiations over the photocatalytic degradation of Acid Red 88 (AR88) azo dye molecules dissolved in water. Enhanced degradation rates were achieved for the Ce-doped samples compared to those of the pure ones. Similarly, the extend of mineralization (i.e., total organic carbon (TOC) removal) reached the maximum value of 54% for the Ce-doped samples under UVA light. According to the scavenging experiment results, it was found that the most effective radical involved in the present photocatalytic degradation reactions was the superoxide anion (·O2−).

Comparative adsorptive performance of adsorbents developed from sugar industrial wastes for the removal of melanoidin pigment from molasses distillery spent wash

Following the expansion of distillery industries, a large quantity of waste is being released to the environment containing high color-forming chemicals. This study aimed at degrading melanoidin pigment from distillery spent wash by using impregnated Sugarcane bagasse activated carbon (SCBAC) and Modified Bagasse Fly Ash (MBFA) as a comparative study. FTIR has revealed functional groups responsible for adsorption. A broad peak revealing an amorphous structure was observed for SCBAC while crystalline structure was observed in MBFA using XRD. SEM micrograph revealed an irregular macro-porous structure and regular structure for SCBAC and MBFA respectively. In the adsorption, important process parameters were optimized in response to color removal efficiency. At equilibrium, adsorption isotherm models, kinetics, mechanisms, and thermodynamics of the adsorption were studied. Langmuir model and Pseudo-second order result in the best fit for both adsorbents. Thermodynamics study revealed an exothermic process, feasibility, and spontaneity of the adsorption process for both adsorbents.

The effect of different types of AOPs supported by hydrogen peroxide on the decolorization of methylene blue and viscose fibers dyeing wastewater.

Wastewater from the textile industry containing a high concentration of organic and inorganic chemicals has strong color and residual chemical oxygen demand (COD). Therefore, advanced oxidation processes (AOPs) are very good candidates to treat textile industry wastewater. In this study, we investigated the effect of different types of AOPs supported with hydrogen peroxide (H2O2) for the treatment of viscose fibers dyeing wastewater. Fenton, photo-Fenton, and Fenton-supported subcritical water oxidation (FSWO) processes were chosen as AOPs to compare the treatment efficiency of viscose fibers dyeing wastewater. The effects of solution pH, Fe2+ concentration, and H2O2 concentration on the treatment of viscose fibers dyeing wastewater were tested. The maximum color and COD removal efficiency was obtained corresponding to pH 2.5 for all oxidation methods when methylene blue (MB) dye solution was used. However, the maximum efficiencies were obtained at pH 3.0 for real textile wastewater decolorization. The MB dye removal efficiency was increased to 97.22, 100, and 100% for Fenton, photo-Fenton, and FSWO processes, respectively, when the addition of H2O2 concentration was adjusted to 125 mg/L. However, the maximum color removal efficiencies of viscose fibers dyeing wastewater were obtained 56.94, 61.26, 64.11% for Fenton, photo-Fenton, FSWO processes, respectively. As a result, the FSWO showed maximum color removal efficiencies.

Reduction of Cost and Environmental Impact in the Treatment of Textile Wastewater Using a Combined MBBR-MBR System.

A hybrid Moving Bed Biofilm Reactor—Membrane Bioreactor (MBBR-MBR) was developed for the treatment of wastewater from a Spanish textile company. Compared with conventional activated sludge (CAS) treatment, the feasibility of this hybrid system to reduce economic and environmental impact on an industrial scale was conducted. The results showed that, technically, the removal efficiency of COD, TSS and color reached 93%, 99% and 85%, respectively. The newly dyed fabrics performed with the treated wastewater were qualified under the standards of the textile industry. Economically, the values of Capital Expenditure (CAPEX) calculated for the hybrid MBBR-MBR system are profitable because of the reduction in Operational Expenditure (OPEX) when compared with CAS treatment, due to the lower effluent discharge tax thanks to the higher quality of the effluent and the decolorizing agent saved. The result of Net Present Value (NPV) and the Internal Rate of Return (IRR) of 18% suggested that MBBR-MBR is financially applicable for implantation into the industrial scale. The MBBR-MBR treatment also showed lower environmental impacts than the CAS process in the life cycle assessment (LCA) study, especially in the category of climate change, thanks to the avoidance of using extra decolorizing agent, a synthetic product based on a triamine.

In situ utilization of biomass pretreatment liquor as a novel flocculant for anion dyes removal: Performance and mechanism

In this work, it was first found biomass pretreatment liquor (PL) produced from rice straw (RS) pretreatment with FeCl3 and polyethylene glycol 400 co-solvent can be used in situ as a new flocculant to remove anionic dyes from wastewater. The removal performance of nine dyes was investigated using various PL doses at different pH values. The experiment indicated that the PL had different flocculation effects on these dyes (color removal efficiency: 42.58–99.84%). Positive color removal results for the dyes were unachievable with six commercial coagulants. Among the nine dyes treated by PL flocculation, the best removal efficiencies for color, turbidity and suspended matter were obtained for Congo red. In the flocculation process, Fe3+ plays a role in charge neutralization, lignin nanoparticles (LNP) relies on hydroxyl groups to react instantaneously with the amino groups on the dye, and are bridged together by π–π interactions to promote the formation of floc clusters until they completely settle. Utilization of PL as a flocculant helps pave the way to simultaneously treat waste biomass, waste treatment liquor and dye wastewater. This research is of great significance for future water environment remediation and material development.

Effect of the bio-inspired modification of low-cost membranes with TiO2:ZnO as microbial fuel cell membranes

Microbial fuel cells (MFCs) are a novel technique for converting biodegradable materials into electricity. In this study, the efficiency of mixed crystal (TiO2:ZnO) as a membrane modifier of a low-cost, antifouling and self-cleaning cation exchange membrane for MFCs was studied. The modification was prepared using polydopamine (PDA) as the bio-inspired glue, followed by gravity deposition of a mixture of catalyst nanoparticles (TiO2:ZnO 0.03%, 1:1 ratio) as anti-biofouling agents. The effects of the membrane modification were evaluated in terms of power density, open circuit potential, coulombic efficiency, anti-biofouling properties and also color and COD removal efficiency. The results showed that the use of the PDA-modified membrane and a mixture of catalysts facilitated the transfer of cations released during the oxidation process in the anodic compartment of the MFC, which increased the power generation in the MFC by 2.5 times and 5.7 times the current compared to pristine and PDA pristine membranes, decreased the MFC operating cycle time from 5 to 3 days, doubled the lifetime of the membranes and demonstrated higher COD removal efficiency and color removal. Finally, SEM and AFM analysis showed that the modification significantly minimized surface fouling. The modified membranes in this study proved to be a potential alternative to the expensive membranes currently used in MFCs, furthermore, this modification could be an interesting alternative modification for other potential membranes for use in MFCs, due to the fact that the catalyst activation was only performed with visible light (artificial and solar), which could decrease operating costs.

Experimental design approach to COD and color removal of landfill leachate by the electrooxidation process

Toxic leachates originate from landfills are one of the major environmental problems. It has an important role in groundwater contamination and its treatment is crucial for environmental protection. In this research, the Electrooxidation (EO) process is applied to the landfill leachate balancing pool effluent. At the beginning of the study, conventional characterization of landfill leachate was conducted. Then, the EO process was progressed via 14 stainless steel and parallel positioned electrodes. Through the Response Surface Methodology (RSM), the effectiveness of process variables was explained statistically. Effects of pH, current density, and reaction time on the process efficiency were studied and optimum conditions of the EO reaction were determined via COD and color removal efficiency parameters. By the model, optimum conditions of the reaction were found to be pH 7, current density 4.30 mA/cm2, and reaction time 35 min. The estimated removal efficiencies for COD and color were 42% and 97%, respectively. R2 values of the models were 98% for color removal and 93% for COD removal.

Geophysical Survey Report for Textile Park Nandgaon Peth MIDC Area District Amravati (M.S.), India

Textile industry is one of the major industries in the world that provide employment with no required special skills and play a major role in the economy of many countries. The textile industry utilizes various chemicals and large amount of water during the production process. Colour is the major pollutants present in the effluent from various textile industries. These are highly toxic to living things and have hazardous effect on their health. Thus removal of colour using natural flocculant is a major step towards the protection of natural resources. Coagulation-flocculation is the most widely used method and is applicable for the removal of the colour even at low concentrations. This paper represents the results of investigations carried out for the removal of colour along with SS, DS, TS and COD from waste water by using natural flocculant i.e. Cactus, Aloevera, and combination of Cactus & Aloevera. The colour removal efficiency of flocculant was investigated by batch wise coagulation flocculation method. The effect of various important parameters on the % removal of colour was studied to find the optimum condition for the maximum removal of colour. The parameters like pH, coagulant dose, flocculant dose, coagulant mixing time, coagulant mixing speed, flocculant mixing time, flocculant mixing speed, setting time & concentration of waste water were investigated. These parameters for Cactus were found to be 12, 10 ml/L, 20 ml/L, 2 min, 140 rpm, 15 min, 70 rpm, 6 min, 300 ml/L respectively, for Aloevera were Journal of Water Resource Engineering & Pollution Studies Volume 5 Issue 1 found to be 11.5, 10 ml/L, 100 ml/L, 2 min, 140 rpm, 15 min, 30 rpm, 1 min, 300 ml/L respectively and simultaneously for combination of Cactus & Aloevera were found to be 12, 10 ml/L, 10% + 80% (Cactus + Aloevera dose) ml/L, 2 min, 140 rpm, 25 min, 50 rpm, 10 min, 300 ml/L respectively. These natural flocculants gives maximum colour removal efficiency in the range 85-100%. The colour removal efficiency was found in between 85-100% for all parameters. All the result was validated on the basis of mathematical analysis. All the graphs were fitted to various trend lines out of which polynomial third order curve is best fit to experimental work as the coefficient of correlation (R2 value) is closer to unity.

Evaluation of color removal efficiencies and kinetic parameters of Fenton (H2O2/Fe2+) and photo-Fenton (H2O2/Fe2+/UV) processes in the treatment of a textile wastewater containing indigo blue / Avaliação da eficiência de remoção de cor e parâmetros cinéticos dos processos de Fenton (H2O2/Fe2+) e foto-Fenton (H2O2/Fe2+/UV) no tratamento de um efluente têxtil contendo corante azul índigo

The textile industry uses Indigo blue dye extensively in the production of jeans. Thus, high volumes of wastewater containing dye are obtained and must be treated before being discharged. The color removal efficiencies of indigo blue dye synthetic wastewater after treatment by Advanced Oxidative Processes (AOPs) using Fenton (H2O2/Fe2+) and photo-Fenton (H2O2/Fe2+/UV) was evaluated in this work. The experiments were conducted at pH 2.8 and evaluated the influence of the amount of [H2O2]/[Fe2+], the use of sulfuric acid and citric acid to adjust the pH, the initial concentration of the indigo dye, and the dosage form of H2O2 - the kinetic parameters and BMG model were also evaluated. The use of sulfuric acid to adjust the pH was more efficient in removing the color. The highest color removal rates were 70.78 ± 2.96 % after 180 min and 64.22 ± 2.08 % after 60 min, respectively, for the Fenton and photo-Fenton processes (both with a single dose of reagents) and 79.76 ± 1.45 % after 300 min and 80.43 ± 1.27% after 180 min, respectively, for Fenton and photo-Fenton with the gradual addition of H2O2. The indigo dye degradation reactions are better suited to the BMG kinetic model.

Performance of combined persulfate and tannin for the treatment of anaerobically treated palm oil mill effluent

<p>The current research was aimed to investigate the performance of combined persulfate oxidation process and tannin via coagulation-flocculation processes as a post treatment of anaerobically treated palm oil mill effluent (AnT-POME). Different dosages of sodium persulfate (Na2S2O8, 238 g/mol) 0.1 (w/v) and modified tannin were combined as a simultaneous reaction to treat AnT-POME. Different dosages of tannin ranged between 0.02g and 0.12g with pH variation ranged between 3 and 11 retention and retention time of (30, 90, 120 and 180) were evaluated. The performance of the treatment processes was evaluated based on the removal of three different parameters namely; chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and color under the following operational conditions: persulfate dosage, tannin dosage, pH and retention time (min). Using persulfate alone, the maximum removal efficiency of COD, color, and NH3-N were 50%, 60% and 22%, respectively by using 4 mL of 0.1 (w/v) persulfate dosage at pH 7 and 60 min retention time. While, the performance of simultaneous reaction improve the removal efficiencies of COD, color, and NH3-N to 90%, 96% and 44%, respectively using 4 mL of 0.1 (w/v) persulfate and 0.06 g of tannin during 120 min retention time at pH 7. However, the maximum removal of NH3-N (59%) was achieved at pH 11. The study revealed that the simultaneous persulfate/tannin reaction is a promising treatment method for industrial wastewater treatment.</p>

Exploring the potential of photocatalytic dual layered hollow fiber membranes incorporated with hybrid titania nanotube-boron for agricultural wastewater reclamation

The emergence of hybrid photocatalytic membranes has provided a new direction in search of efficient technologies to separate and degrade pollutants present in wastewaters. Colour pigments originated from different sources including agricultural waste pose serious threats towards water bodies as their presence will lead to multiple environmental problems. This study investigated the potential of a photocatalytic dual layered hollow fiber membrane (DLHFM) incorporated with boron doped titania nanotubes (TNT-B) photocatalyst for the photodegradation and removal of colour pigment molecules present in aerobically treated palm oil mill effluent (AT-POME). The colour removal efficiencies and separation performance of the DLHFM were evaluated through a submerged membrane photo reactor (SMPR) system driven by visible light. Polyvinylidene fluoride-based DLHFM loaded with 2% of photocatalyst (PVDF-L2%) exhibited the best membrane performance with a flux of 39.62 L/m2h and colour removal efficiency of 79.42%. The controlled distribution of photocatalysts as well as the synergistic combination of membrane filtration and photodegradation concertedly contributed to the improvement in membrane’s performance. 95% of flux and colour removal efficiency were sustained after four filtration cycles. The membrane exhibited efficient performance in terms of consistent flux and colour removal efficiency after 20 days of continuous photocatalytic filtration, implying their high long-term stability. This study highlights the efficiency and potential of visible light photocatalytic membranes in treating colour laden wastewaters.

Electrocoagulation technique for continuous industrial licorice processing wastewater treatment in a single reactor employing Fe-rod electrodes: Process modeling and optimization and operating cost analysis

Licorice processing industry produces a characteristic wastewater with a high chemical oxygen demand (COD), high turbidity, and intense color. Direct disposal of untreated licorice processing wastewater into water bodies can pose a serious risk to the human health and environment. The main objective of this study is to evaluate the performance of a novel laboratory scale continuous electrocoagulation (EC) reactor using iron (Fe) rod electrodes (anode and cathode) for treating a real licorice processing wastewater. Response surface methodology (RSM) was employed to investigate the effects of important parameters such as: current density (CD), electrolysis time, mixing intensity, and NaCl concentration for Fe rod electrodes on the removal efficiency of color, soluble COD (sCOD), and turbidity. In order to evaluate the effect of reactor design on the overall process performance, the results were compared with our previous study in which Fe plate electrodes were employed in an identical system. The process exhibited better performance in terms of turbidity removal for Fe rod electrodes with an average value of 59.35% in contrast to Fe plate electrodes (47.88%). Color and sCOD removal efficiencies of 94.6% and 90.1% were achieved, respectively for the EC system using Fe rod electrodes under optimum conditions: electrolysis time (71.8 min), CD (28 mA/cm2), mixing intensity (45 rpm). While in the EC reactor using Fe plate electrodes, the optimum (electrolysis time of 81.8 min, current density of 35 A/cm2, and mixing intensity of 45 rpm) color and sCOD removal were obtained 90.1% and 89.4%, respectively. Analysis and comparison of the data revealed that Fe rod electrodes delivered a better treatment performance than Fe plate electrodes, taking into account that the optimum electrolysis time and applied current density were considerably lower for the Fe rod electrodes. Overall, these results confirmed that the novel EC reactor using Fe rod electrodes can reduce the operating cost and be proposed as a pragmatic approach to remove high amount of color, COD, and suspended solids from licorice processing wastewater.

COD removal, decolorization, and energy consumption of electrocoagulation as a wastewater treatment process

The efficiency of color and COD removal in wastewater treatment is one of the essential factors. High color removal can encourage the reuse of wastewater as raw material in the recycled paper industry. Electrocoagulation (EC) process is effective pollutant removal in wastewater due to the adsorption, coagulation, and flotation. In this study, recycled paper industrial wastewater was used; this type of waste has a high content of disturbing pollutants, and treatment with electrocoagulation has not been widely carried out for this type of waste. EC treatment has a relatively high level of effectiveness to remove these pollutants; the influential factors studied include initial pH, applied current, supporting electrolyte, and processing time on a laboratory scale. The degradation of color, COD, and energy used was also evaluated. The best color removal was obtained as 100% at 80 minutes of process, and a COD concentration is 147 mg/L, and the energy used is 13.56 kWh/L.

하수처리수의 3차처리를 위한 고도산화법(AOP)의 적용성에 관한 연구

Ozone has been applied in combination with various processes for the tertiary treatment of municipal wastewater. However, in Korea, the ozone process is mainly employed for the reuse of tertiary treated wastewater, and an enhanced advanced oxidation process (AOP) is needed to realize the large-scale reuse of treated wastewater. In this study, various AOPs employing ozone (only ozone process, O₃+H₂O₂, O₃+UV, O₃+GAC) were used to analyze the TOC, CODcr, and color treatment efficiencies of municipal wastewater and evaluate its applicability of wastewater reuse. The O₃+H₂O₂ process showed the highest TOC removal efficiency of 62.0%, while the O₃+GAC and only ozone processes exhibited the TOC removal efficiencies of 58.9% and 59.3%, respectively. The TOC removal pattern of the O₃+UV process was similar to that of the O₃+H₂O₂ process. The TOC removal efficiency of the O₃+UV process, 61.0%, was slightly lower than that of the O₃+H₂O₂ process. The CODcr removal efficiencies of the O₃+UV and O₃+H₂O₂ processes were 75.8% and 77.0%, respectively. However, the TOC and CODcr removal efficiencies were different within the error range, so there was no significant difference in the processing efficiencies of the methods investigated. The color removal efficiencies of the O₃+UV (57.8%) and O₃+H₂O₂ (57.4%) processes were 57.8%, 57.4%. respectively and it showed similar pattern.

Application of coke breeze for removal of colour from coke plant wastewater

Treatment of coking waste water has always been a challenge because of its complex and toxic nature. Numbers of technologies like biological treatment, advanced oxidation processes, activated carbon treatment etc. are available for removal of color and organic contaminants from wastewater. However, challenges and problems associated with application of biological, advanced oxidation methods for removal of color, chemical oxygen demand (COD), cyanides led to thrust for the development of new promising technologies. In this study, the application of coke breeze for the treatment of wastewater through adsorption has been demonstrated. A pseudo second order reaction kinetics has been observed through batch process adsorption study. Furthermore, adsorption data has found to be best fitted with the Freundlich adsorption isotherm model. Color removal efficiency of 80–90% along with COD removal efficiency of 40–50% was observed within 30 min by 120 g/L dosage of the adsorbent. The removal of phenolic and other organic compounds from coking wastewater has been measured through UV–Vis spectroscopy. The morphological changes of the adsorbent coke breeze have been captured through scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. However, because of the significant abundance in the steel plant, cost effectiveness and applicability of the post-treated coke breeze in sintered plant as fuel, turn it into a suitable adsorbent despite of having much lower specific surface area compared to commercial activated carbon (AC). Therefore, application of the coke breeze turns it into a very promising material and the technique is sustainable towards the coke quenching effluent treatment.

A comprehensive study on opium pharmaceutical wastewater treatment in laboratory and semi-industrial scales

The wastewater of an opium pharmaceutical industry was successfully treated using a combined process of electrocoagulation/flotation (ECF), peroxone (H2O2/O3) and adsorption filter of granular activated carbon (GAC) in a three-step operation (ECF → H2O2/O3 → GAC), in a lab and semi-industrial scales. The effect of the operating parameters such as initial pH, current density, residence time, injection dose of H2O2, the ratio of H2O2/O3 and time of adsorption process was optimized in both scales. On the lab-scale, the removal efficiency of COD, Color, TDS, TSS, electrical power consumption, electrode consumption, and operating costs have been studied. In the ECF process, the maximum removal efficiencies of COD, color, TDS and TSS were 64%, 60%, 61% and 50%, respectively. The optimum pH, ozonation time, hydrogen peroxide concentration and the ratio of H2O2/O3 in the peroxone process are 8, 45 min, 900 mg/l, 0.3 H2O2/O3, respectively. After ECF and peroxone processes, the maximum removal efficiencies of COD and color increased up to 84% and 62% and after the adsorption process, the maximum removal efficiencies of COD, Color, TDS, and TSS increased up to 99.2%, 99.0, 99.0 and 99.1%, respectively. The performance of each reactor in the semi-industrial scale was also evaluated. After the treatment operation in the ECF → H2O2/O3 → GAC semi-industrial pilot reactor, the COD removal efficiency, Color, TDS and TSS of opium wastewater reached 96%, 99%, 99% and 99%, respectively. The excellent performance, as well as the low operating cost, confirmed that this integrated system is highly applicable for the advanced treatment of opium pharmaceutical industry wastewater.

Innovative Ag–TiO2 Nanofibers with Excellent Photocatalytic and Antibacterial Actions

Ag–TiO2 nanostructures were prepared by electrospinning, followed by calcination at 400 °C, and their photocatalytic and antibacterial actions were studied. Morphological characterization revealed the presence of one-dimensional uniform Ag–TiO2 nanostructured nanofibers, with a diameter from 65 to 100 nm, depending on the Ag loading, composed of small crystals interconnected with each other. Structural characterization indicated that Ag was successfully integrated as small nanocrystals without affecting much of the TiO2 crystal lattice. Moreover, the presence of nano Ag was found to contribute to reducing the band gap energy, which enables the activation by the absorption of visible light, while, at the same time, it delays the electron–hole recombination. Tests of their photocatalytic activity in methylene blue, amaranth, Congo red and orange II degradation revealed an increase by more than 20% in color removal efficiency at an almost double rate for the case of 0.1% Ag–TiO2 nanofibers with respect to pure TiO2. Moreover, the minimum inhibitory concentration was found as low as 2.5 mg/mL for E. coli and 5 mg/mL against S. aureus for the 5% Ag–TiO2 nanofibers. In general, the Ag–TiO2 nanostructured nanofibers were found to exhibit excellent structure and physical properties and to be suitable for efficient photocatalytic and antibacterial uses. Therefore, these can be suitable for further integration in various important applications.

Efficacy of Acid-treated Sawdust in Decolourization of Tanning Wastewater

Colour removal from dye-bearing effluent is a serious challenge due to the difficulty in treating such wastewater by conventional treatment methods. The present investigation explores the decolourization of contaminated wastewater using acid-activated sawdust as an adsorbent. The physicochemical properties of wastewater samples labelled A, B, and C vizaverage temperature; pH; electrical conductivity; and total dissolved solids were determined using standard methods to be 302.63; 6.1; 284.47 µS/cm;35116.66 mg/L respectively. Colour removal efficiency of the adsorbent was studied under variable conditions (contact time, rate of agitation,loading). Experimental results demonstrated that the sawdust adsorbent has a significant capacity for colour removal from tannery effluent. There was significant variation in the absorbance of the treated samples. Adsorbent dose, stirring rate, and contact time were found to be directly proportional to colour removal while pH variation of the samples show that the effluents became less alkaline (slightly acidic) after decolourization.

Tannin-based coagulant for harvesting microalgae cultivated in wastewater: Efficiency, floc morphology and products characterization

Tannin-based coagulants (TBCs) have the potential to be used to harvest microalgae cultivated at wastewater treatment plants. Their use would address the circular economy associated with the production of low-toxicity biomass and supernatant. Studies in this field are still scarce, and substantial gaps exist in the definitions of the flocculation process parameters. In this context, the objective of this work was to evaluate TBC performance as a natural coagulant for harvesting microalgae biomass grown in sanitary effluent digested in an up flow biofilter, as well establishing a path to enable recovery and reuse of wastewater nutrients. Classical removal techniques combined with image analysis and light scattering-based equipment were used to evaluate the coagulant performance, recovery efficiency, floc strength, and floc recovery compared to aluminum sulfate (AS). The results showed that TBC was able to efficiently harvest algal biomass from the effluent, achieving color, turbidity, and optical density (OD) removal efficiencies greater than 90% with only 5 min of sedimentation. The optimal harvesting dosage was 100 mg·L−1 for TBC and 75 mg·L−1 for AS. TBC presented the advantage of harvesting biomass without changing the pH of the medium and was also able to present satisfactory removal of the analyzed parameters (color, turbidity and OD) at pH values of 5.0, 7.0, and 8.5. In addition, TBC produced stronger flocs than AS, showing a better ability to resist breakage upon sudden shear rate variations. TBC produced macronutrient-rich biomass and supernatant that was similar to that produced with AS.