Printing And Dyeing Wastewater Research Articles

Efficient Sb(Ⅲ) removal from printing and dyeing wastewater using TiCl4 as a potential coagulant instead of polyferric sulfate

With increasing health concerns and the tightening of discharge standards, there is growing demand for more efficient Sb(Ⅲ) removal from printing and dyeing wastewater (PDW). Currently, the most common coagulant used in Sb removal in industry is polyferric sulfate (PFS). However, the residual Fe ions in the effluent cause colorimetric problems and irreversibly damage the membrane components during the subsequent reverse osmosis treatment process. Therefore, identifying novel coagulants to replace PFS in the removal of Sb(Ⅲ) is necessary. In this study, TiCl4 was employed for in-situ hydrolysis to produce flocs for Sb(Ⅲ) removal in simulated and real PDW. TiCl4 exhibited an excellent performance compared to PFS in terms of dosage, turbidity, application pH, and anti-interference properties. Sb(Ⅲ) removal of 97.3 % was realized at a dosage of 30 mg/L and a final pH of 5.0 in slightly contaminated PDW, whereas PFS required a higher dosage, resulting in higher disposal costs. Furthermore, the application of TiCl4 led to lower turbidity and reduced secondary contamination. An investigation of the co-existing ions revealed that TiCl4 was considerably more tolerant than PFS toward PO43–, humic acid, and silicate at a lower concentration. Simultaneously, Sb(Ⅲ) was partially oxidised to Sb(Ⅴ) during removal, but TiCl4 exhibited lower oxidative properties. The results of PDW treatment indicated that TiCl4 could realize 85.6 % Sb(Ⅲ) removal at a dosage of 30 mg/L, and the pre-reduction of Sb(Ⅴ) to Sb(Ⅲ) was a safe, effective treatment. The results of zeta potential measurements and X-ray photoelectron spectroscopy revealed that Sb(Ⅲ) removal was mainly realised via chemical adsorption. Overall, this study provides a promising alternative material for use in practical Sb(Ⅲ) removal from PDW, particularly for reducing coagulation sludge, operational costs, and damage during the possible subsequent reverse osmosis process.

Removal of Congo red dye from industrial effluents using metal oxide-clay nanocomposites: Insight into adsorption and precipitation mechanisms

The efficacy of magnesium oxide (MgO)-bentonite clay nanocomposite particles (MgO nanoparticles embedded in powdered bentonite clay) for water and wastewater treatment applications is examined herein. Congo red (CR), a widely used azo dye, was used as the model contaminant. For CR concentrations ≤120 mg/L, the optimum nanocomposite dosage was ≤1 g/L, achieving CR removal ≥99% for contact times (mixing durations) ≤10 min, whereas temperature and pH had no significant effect on the treatment process. The removal of CR dye followed the pseudo-second-order model than the first order model. Furthermore, adsorption isotherms followed the Langmuir adsorption isotherm rather than the Freundlich adsorption isotherm (R2 ≥ 0.99), hence confirming monolayer homogenous adsorption. The surface morphological and physicochemical characteristics of the nanocomposite were also identified, and results suggest that CR removal was governed by electrostatic attraction between the protonated hydroxyl groups (i.e., -OH2+), embedded on the nanocomposite surface, and the negatively charged –SO3-groups of the CR dye. When used for the treatment of real printing ink wastewater, CR was practically removed (⁓100%), whereas for real printing and dyeing wastewater (PDW), a more challenging effluent that also contains salts and other contaminants, CR removal was ≥80%. Overall, the produced MgO-bentonite clay nanocomposite hold great promise for sustainable CR removal, a typical contaminant that is released by many industries including printing, tannery and textile, paper, plastic, and paint and coatings.

Mechanism for the synergistic removal of Sb(Ⅲ) and Sb(V) from printing and dyeing wastewater by polyferric sulfate

Herein, the synergistic removal of Sb(Ⅲ) and Sb(Ⅴ) from wastewater by polymeric ferric sulfate (PFS) and the oxidation process were investigated. The results showed that PFS exhibited superior performance on Sb(Ⅲ) removal in terms of coagulant dosage, applied pH, and anti-interference properties than Sb(V) removal. For the Sb liquid in pure water matrix (Sb=1000 μg/L), when the dose was 60 mg/L and the final pH was 5.0, the independent removal of Sb(Ⅲ) and Sb(V) was 95% and 90%, respectively. Meanwhile, Sb(Ⅲ) removal in the PFS coagulation system remained stable within a wider pH range (pH=3–9). Sb(Ⅲ) could be preferentially removed in the solution column and had an inhibitory effect on the adsorption of Sb(V). Sb(Ⅲ) was also partially oxidized to Sb (V) during the coagulation process, which was influenced by the coagulant dosage and the solution pH. The results of the actual printing and dyeing wastewater (PDW) treatment indicated that the pre-reduction of Sb(V) to Sb(Ⅲ) could significantly increase the total Sb removal from 72.0% to 97.5%. The characterization results, such as Zeta potential and x-ray photoelectron spectroscopy (XPS), indicated that the Sb(Ⅲ) removal by PFS was achieved mainly through chemical adsorption. While the Sb(V) removal was realized by both chemical adsorption and electrostatic adsorption, the electrostatic adsorption contributed more than the chemical adsorption. This study provides a new idea for understanding the synergistic removal of Sb(Ⅲ) and Sb(V) using PFS in PDW advanced treatment.

Hierarchical Porous Aerogels With Multiple Adsorptive Interactions for Dye Wastewater Purification.

Aerogels present a huge potential for removing organic dyes from printing and dyeing wastewater (PDW). However, the preparation of aerogels with multiple dye adsorption capabilities remains a challenge, as many existing aerogels are limited to adsorbing only a single type of dye. Herein, a composite aerogel (CG/T-rGO) with the addition of carboxymethyl chitosan, gelatin and tannic acid reduced graphene oxide (T-rGO) was synthesized by freeze-drying technology. The electrostatic interactions between dye molecular and GEL/CMCS (CG) networks, as well as the supramolecular interactions (H-bonds, electrostatic interactions and π-π stacks) between T-rGO, have endowed the aerogel with the ability to adsorb multiple types of dye, such as methylene blue (MB) and methyl orange (MO). Results exhibited that the prepared CG/T-rGO aerogel possessed strong mechanical strength and a porous 3D network structure with a porosity of 96.33 %. Using MB and MO as adsorbates, the adsorption capacity (88.2 mg/g and 66.6 mg/g, respectively) and the mechanism of the CG/T-rGO aerogel were investigated. The adsorption processes of aerogel for MB and MO were shown to follow the pseudo-second-order kinetic model and Langmuir isotherm model, indicating the chemical adsorption of a monolayer. The proposed aerogel in this work has promising prospects for dye removal from PDW.

Treatment of printing and dyeing wastewater using Fenton combined with ceramic microfiltration membrane bioreactor

The release of printing and dyeing wastewater (PDW) into the environment is a concern attributed to its acute, chronic and cytotoxic effects to aquatic life. Two anaerobic/aerobic-membrane bioreactors (A/O–MBRs) were operated continuously to treat raw (untreated) and Fenton oxidized PDW. After about 70 days acclimatization, 67% of the chemical oxygen demand (COD) and 35% of adsorbable organic halogens (AOX) were removed by direct biodegradation in A/O–MBR without Fenton pre-treatment, while 90% of the COD and 79% of AOX were removed in Fenton + A/O–MBR system. Fenton oxidation play a dominate role on the COD and AOX removal of PDW in the combination system. The Fenton pre–treatment of PDW could remarkably reduce membrane fouling. The Shannon indices showed that the microbial diversity in anaerobic flocs were significantly higher than the microbial diversity in aerobic flocs in both two A/O–MBR systems. The metagenomics analysis found that the key functional genes responsible for the AOX biodegradation were EC3.1.1.45, pcaI, and pcpD. The transcript per million (TPM) abundance of EC3.1.1.45 and pcaI significantly up-regulated in both anaerobic and aerobic flocs after 70 days acclimatization. Based on the pilot applications study, the total operation cost of Fenton + A/O–MBR processes for PDW remediation was approximately 1.263–1.384 USD/t. This study provides a promising technique for removing AOX and other organic contaminants from PDW.

Synergizing redox of zerovalent iron and singlet oxygen to remove aniline, chromium and antimony in printing and dyeing wastewater synchronously: Multifunctional effect of sludge derived biochar

Printing and dyeing wastewater (PDW) with complex water matrix generally contains ubiquitous organic pollutant (e.g., aniline) and heavy metals (e.g., Cr(VI) and Sb(III)), aggravating their environmental risks and remediation difficulty. To date, little is known about the synchronous removal of aniline, Cr(VI) and Sb(III) because ternary processes including oxidation, reduction and adsorption need to function synchronously. Herein, we proved multiple redox active centers (e.g., Fe-containing moieties, C-containing moieties and PFRs) present in sludge derived biochar (SDBC), which ensured synchronous degradation of aniline, reduction of Cr(VI) and oxidation of Sb(III) over a wide pH range. Results demonstrated that degradation of aniline was mainly attributed to singlet oxygen (1O2), originating from activating O2 to O2− and 1O2 by SDBC without any external oxidants. Cr(VI) was reduced to Cr(III) by reductive active species (i.e., O2− and Fe-containing moieties: zerovalent iron (Fe(0)) and Fe(II)), while Fe(0) triggered the dominant Cr(VI) reduction. The conversion of Sb(III) to Sb(V) was ascribed to Fe(III) and C = O moiety, and Fe(III) supported the major Sb(III) oxidation. The generated Cr(III) and Sb(V) could be further immobilized onto SDBC through electrostatic attraction, complexation and precipitation. Overall, this study provides a novel understanding on recycling sewage sludge to functional biochar accompanied by carbon-storage, while offering a promising strategy for the simultaneous removal of multicomponent contaminants in practical PDW.

Electro-Fenton oxidation of printing and dyeing wastewater with CO2 activated CuFeC and CuMnC aerogel cathode

An electro-Fenton (EF) system with CuFeC and CuMnC aerogel cathodes was proposed without an additional Fe2+ or H2O2 for the efficient degradation of actual printing and dyeing wastewater (PDW). The CO2 activated CuFeC aerogel as the cathode showed the highest chemical oxygen demand (COD) removal efficiency compare to other cathodes. Structural characterization revealed that CO2 activation significantly enlarged the cathode porosity and surface area to increase the exposure of active sites to catalysis. During a 60 min experiment, the COD removal in the EF system with CO2–activated CuFeC and CuMnC aerogel cathodes reached 72.8 % and 51.5 %, respectively. The high COD removal of PDW with CO2-activated CuFeC aerogel could be achieved at a wide range of pH values (3~8). The enhanced mineralization efficiency of the CuFeC aerogel was mostly attributed to the synergistic effect between Fe and Cu, which benefited the oxygen reduction reaction (ORR) ability to produce more H2O2 and generate more in-situ ·OH. The possible oxidation pathway of 2, 4, 6-trichlorophenol was proposed via an intermediate study. Moreover, the CO2–activated CuFeC aerogel presented low Fe and Cu leaching in an acidic solution and a long operational life span. This material can provide a feasible way for actual PDW purification through the EF process.

Preparation of High-Performance Zn-Based Catalysts Using Printing and Dyeing Wastewater and Petroleum Coke as a Carrier in Acetylene Acetoxylation

In this study, novel Zn catalysts were prepared by the wet impregnation method using printing and dyeing wastewater (PDW)-modified petroleum coke (petcoke) as a carrier, and they were applied to the acetylene acetoxylation. The pretreated petroleum coke has a high specific surface area which provides sufficient space for the loading of Zn. Calcination further increases catalyst activity, but when calcination temperatures exceed 1000 °C, a significant loss of Zn occurs, resulting in a dramatic decrease in catalyst activity. This enables the conversion of acetic acid up to 85%. X-ray photoelectron spectroscopy confirmed that a large amount of N is introduced into PC from PDW, which changes the electron transfer around Zn. Temperature-programmed desorption (TPD) analysis revealed that the nitrogen-doped Zn(OAc)2 catalyst enhanced the catalytic activity by modulating the intensity of the catalyzed adsorption of acetic acid and acetylene. This study provides a new way to reuse petroleum coke and printing and dyeing wastewater to support the sustainable development of the vinyl acetate industry.

Insight into dissolved organic nitrogen transformation and characteristics: Focus on printing and dyeing wastewater treatment process

Textile industry discharges large amounts of printing and dyeing wastewater (PDW) containing high concentration of refractory dissolved organic nitrogen (DON). However, the DON transformation and characteristics during PDW treatment, and its potential environment impact receive little concern. Treatment groups of dyeing wastewater (G-RB5), printing wastewater (G-Urea) and domestic wastewater (G-NH4Cl) with Reactive Black 5 (RB5), Urea and NH4Cl as influent nitrogen species were set to compare the DON behavior during the hydrolytic acidification-aerobic-anoxic process. G-RB5 exhibited higher DON concentrations with greater fluctuations, and its effluent dominated low molecular weight (LMW) and hydrophilic DON, showing high bioavailability (67.6%) and low biodegradation (8.0%). In the aerobic section, the concentration of microorganism-derived DON in G-RB5 was higher but the nitrogen species were fewer than G-Urea and G-NH4Cl. Grey relational analysis revealed that Proteobacteria and Thauera were the common bacteria strains showing high association degree (γ > 0.9) with biodegradable DON (ABDON) in all groups; while microbes related with biodegradable DON (BDON) varied between groups. The higher contents of DON, ABDON, LMW-DON and hydrophilic DON induced by RB5 highlight the importance of controlling DON from textile industry to mitigate the potential risk like algae growth stimulation, which needs more attention in future.

Achieving multi-cycle regeneration of activated carbon and Cr(VI) removal over a wide pH range by hydrothermal converting quinonimine dye into difunctional pyrrolic-N: Implication for carbon capture in printing and dyeing wastewater treatment

Activated carbon (AC) adsorption is a prevalent method for printing and dyeing wastewater (PDW) treatment, but restricted by adsorption active site depletion. The regeneration by thermal desorption or chemical oxidation is liable to destroy carbon skeleton as well as consume carbon composition, leading to few service cycles. The desorption and decomposition of absorbed dye trigger CO2 greenhouse gas and secondary pollutant emission. Herein, we establish a sustainable hydrothermal regeneration for methylene blue (MB) exhausted AC. The absorbed MB was converted to its pyrrolic-N-containing hydrochar attached on regenerated AC through hydrothermal hydrogenation and rearrangement reaction. The generated pyrrolic-N supported 11 adsorption-regeneration cycles caused by the property shift from physisorption to chemisorption. Meanwhile, pyrrolic-N loaded on regenerated AC counteracted the negative impact of electrostatic repulsion and low redox potential at high pH for Cr(VI) reductive removal, recycling final regenerated AC over a wide pH range of 3.0–9.0 for Cr(VI) removal via direct electron donation. This approach is tailored to the dyes with the same quinonimine group as MB. Overall, the carbon capture for the simultaneous removal of dye and Cr(VI) in PDW can be implemented, while providing a novel green methodology to fabricate pyrrolic-N-loaded carbon material.

Study of the adsorption of methylene blue by phytoremediation-plant biomass carbon

Many kinds of plant biomass are used to prepare the plant biomass carbon (PBC) to treat printing and dyeing wastewater (PDW). However, few researchers have studied how effectively PBCs prepared from phytoremediatory plants after phytoremediation can treat the wastewater. Furthermore, whether new pollutants are introduced is an urgent issue that needs interrogation. Thus, the purposes of this study were (1) to gather data on the technical parameters, effects, and mechanism of methylene blue (MB) absorption by PBC prepared from Brassica juncea harvests containing Pb and Cd, and (2) to evaluate the environmental risks associated with the addition of Pb and Cd to PDW. PBC0 and PBC1 were both alkaline with a honeycomb porous structure and an uneven surface. The surface area of PBC1 was much larger than that of PBC0, and PBC1 had more micropores. The hydroxyl group (–OH) and the stretching vibration of CO could interact with MB molecules by hydrogen bonding and electrostatic attraction. In addition, PBCs attracted MB molecules through π-π bond formed by the aromatic CH bending, and the surface complexation would be formed by the interaction between MB molecules and Pb/Cd-O bond in the adsorption of MB by PBC1. The best technical parameters for B. juncea PBC were a PBC quality to wastewater volume ratio of 2.5 t/1000 m3, 50 mg/L; the mode of action and adsorption time set to oscillation for 6 h; a pH of 5; and single use of the PBC. Furthermore, there was no environmental risk during the preparation of PBC1 and in the adsorption process within the scale of this experiment.

Spatiotemporal distribution of microorganisms in a full-scale anaerobic baffled reactor–anoxic/oxic treatment plant for printing and dyeing wastewater

This study purposed to reveal the spatiotemporal variations of functional microorganisms in a full-scale anaerobic baffled reactor (ABR)–anoxic/oxic (A/O) treatment plant for treating printing and dyeing wastewater (PDW). Proteobacteria, Chloroflexi, and Bacteroidetes were identified as three predominant phyla in both ABR and A/O reactors in all seasons. Microbial genera including Thauera, Mesotoga, Acinetobacter, Pseudomonas and Longilinea were identified as important decolorizing bacteria in the ABR, whereas the nitrifying bacteria (Nitrospira and Candidatus Nitrocosmicus) and denitrifying bacteria (Amphiplicatus and SM1A02) promoted the removal of nitrogenous compounds. Network analysis presented that the highest functional unit diversity of microbial community and the strongest positive interaction (92.63 %) between microbes were observed in spring, indicating that the microbial community had a strong cooperative and symbiotic relationship in this season. Moreover, the seasonal and spatial preferences of Thauera, Pseudomonas and Longilinea were discovered, which provides the foundation for controlling microbial communities in different compartments of the ABR and different seasons. This study revealed the correlations between functional microorganisms and factors involved in PDW treatment, and the findings expand the understanding of the dynamical microbial communities associated with PDW treatment in the ABR-A/O system.

The Fate and Transport of Chlorinated Polyfluorinated Ether Sulfonates and Other PFAS through Industrial Wastewater Treatment Facilities in China.

Wastewater from certain industrial processes can be primary emission sources of per- and polyfluoroalkyl substances (PFAS) and fluorinated alternatives like chlorinated polyfluorinated ether sulfonates (Cl-PFESA). Two such industrial processes are electroplating and textile printing and dyeing (PD). This study focused on the fate of Cl-PFESA in wastewater from these two industrial processes, in comparison to other PFAS, as they went through different wastewater treatment plants located in southeast China. The total target PFAS concentrations were 520 ± 30 and 4200 ± 270 ng/L at the effluents of the PD WWTP and electroplating WWTP, respectively. Specifically, 6:2 Cl-PFESA (18%) and 8:2 Cl-PFESA (0.7%) were abundant in electroplating-wastewater. Cl-PFESA were also detected in PD wastewater but at trace concentrations and were likely present due to diffuse emissions. The dissolved-phase Cl-PFESA and PFAS mass flows through the WWTPs were fairly constant throughout both facilities. The majority of Cl-PFESA was captured by sludge sedimentation. However, there were individual treatment processes that could cause the wastewater concentrations to fluctuate, and also could lead to relative enrichment of specific Cl-PFESAs as indicated by the 6:2/8:2 Cl-PFESA ratios. Cl-PFESA and perfluoroalkyl sulfonic acids were more influenced by the investigated treatment processes than perfluorocarboxylic acids.

Abundance Change of Antibiotic Resistance Genes During PDWW Recycling and Correlations with Environmental Factors

Research on the distribution of antibiotic resistance genes (ARGs) in urban sewage treatment systems is extensive, but there is still insufficient research on their abundance in industrial wastewater recycling systems. In this study, a printing and dyeing wastewater (PDWW) recycling system was constructed, and 16S rDNA and high-throughput sequencing technology was used to analyze the microbial communities and ARG abundance during the treatment process. A total of 52 ARGs in nine categories were detected, of which the relative abundance of β-lactam resistance genes was the highest. During the treatment cycle, the concentration of aromatic pollutants increased with an increase in the number of cycles, while the abundance of β-lactam resistance genes increased first, decreased, and then increased (reaching 61.85% on the 100th day). At the same time, the abundance of Firmicutes, Actinobacteria, and Cyanobacteria related ARGs decreased significantly (by 84.66%, 64.38%, and 85.15%, respectively). More than 21 kinds of ARGs were significantly affected by the enrichment by the aromatic pollutants. Among them, 6 kinds of ARGs were significantly positively correlated with changes in the concentrations of the aromatic pollutants (P<0.01), while 6 were significantly negatively correlate (P<0.01). These results show that the abundance of ARGs was affected by the microbial communities and the aromatic pollutants, which increased at first, decreased, and then increased during the PPDW recycling process. This study reveals the effects of the enrichment of aromatic contaminants and changes in microbial communities on ARGs during PPDW recycling, and provides theoretical guidance for the recycling of PDWW to reduce environmental pollution associated with ARGs.

Metagenomic Insights into Salinity Build-up in Microbial Communities and Metabolism of Hydrolytic Bioreactor Treating High-color PDWW

In this study, to solve the problem of salinity enrichment in industrial wastewater recycling, a hydrolytic bioreactor was continuously operated to treat high-color printing and dyeing wastewater (PDWW) with salinity build-up. Nearly complete color removal was achieved even with salinity build-ups from 0.5 to 4 g·L-1 in the influent. Pyrosequencing of 16S rRNA genes showed that the salinity build-up results in the decrease of microbial species from 882 to 631; however, the biodiversity of the bacterial community remains stable. Metagenomic analysis indicated that salinity build-up caused no obvious effect on the overall function of the bacterial community, but altered the abundance of specific decoloring genes. Proteobacteria dominated in the bioreactor, and Methanothrix and Geobacter were the dominant genera under low salinity conditions. Proteobacteria increased in abundance with salinity build-up. Desulfovibrio and Desulfococcus were the two predominant genera in the bioreactor fed with sodium sulphate salinity build-up, demonstrating opposite responses to the sodium stress. PICRUSt functional analysis showed that the relative abundance of the decolorizing enzymes SOD1 and SOD2 decreased significantly, but the relative abundance of CAT and TYR increased, ensuring the stability of the decolorizing function of the hydrolysis biological system. From the perspective of the functional genes of hydrolysis decolorization, this study explored the effect of salinity build-up on the microbial community and function of hydrolysis, providing a theoretical basis for the study of decolorization and organic matter removal mechanism of PDWW under the condition of salinity build-up.

How can accumulated organics and salts deteriorate the biological treatment unit in the printing and dyeing wastewater recycling system?

Wastewater recycling is an effective way to reduce the fresh water supply and pollutant discharge for industry. Nevertheless, wastewater recycling will inevitably lead to the accumulation of inorganic ions and organic pollutants, which can deteriorate the activated sludge system. A printing and dyeing wastewater (PDWW) recycling system was established in this study to investigate the mechanism of biological treatment system deterioration due to organic and inorganic pollutant accumulation. It was found that organic matter accumulation especially intermediate products of added dyes and auxiliaries is crucial for the biological treatment unit deterioration during the beginning of closed-loop PDWW recycling (first 40 days). In addition, inorganic salt accumulation, such as Ca2+, Na+, K+, SO42− and Cl−, can make it even worse afterwards. The results indicated that phenylalanine metabolism, synthesis and degradation of ketone bodies, butanoate metabolism and pyruvate metabolism were the four most significantly influenced metabolic pathways in the PDWW recycling system attributed to the organic matter accumulation. In addition, accumulated inorganic salts could inhibit glycan biosynthesis and metabolism, xenobiotic biodegradation and metabolism and lipid metabolic pathways in the PDWW recycling system, which ultimately deteriorated the biological treatment system.

Tracking variation of fluorescent dissolved organic matter during full-scale printing and dyeing wastewater treatment

In this study, fluorescent dissolved organic matter (FDOM) in real printing and dyeing wastewater (PDW) during full-scale two-stage treatment was characterized using excitation-emission matrix (EEM), apparent molecular weight (AMW) cutoff by centrifugal ultrafiltration and high-performance liquid chromatography with fluorescence detector (HPLC-FLD). EEMs of PDW during treatment were relatively invariable with two typical and dominant peaks (P1, 275/320 nm and P2, 230/340 nm). The removal rates of P1 intensity and P2 intensity were both lower than those of DOC or UVA254 during the 1st stage and 2nd stage treatment. The <3 kDa fraction made major contribution to DOC, UVA254, P1 and P2 intensity. The DOM fractions with different AMW exhibited different removal behaviors during the 1st stage and 2nd stage treatment. The <3 kDa fraction of FDOM was poorly removed by biological treatment alone. The HPLC-FLD multi-emission scan results indicated that the major part of FDOM clusters were hydrophilic and they were more difficult to remove than the transphilic and hydrophobic FDOM clusters. According to the physicochemical properties of FDOM in PDW, selective adsorption and advanced oxidation process could be prior options for PDW advanced treatment.

Comparison of Different Enhanced Coagulation Methods for Azo Dye Removal from Wastewater

Printing and dyeing wastewater (PDW) is considered to be one of the most difficult industrial wastewaters to treat because of its large quantities, high pH values, and high color and toxicity, which may endanger the lives of animals and humans. In this study, we assessed the chemical decolorization process of Congo Red in azo dyes using response surface methodology (RSM), and the effect of different enhanced coagulation pretreatment processes (ECPPs) on the microbial community structure of PDW using high-throughput sequencing technology. We concluded that, based on the initial concentration and pH of Congo Red, different decolorants can be selected for decolorization reactions. In addition, it was found that the microbial community of the wastewater after three different ECPP treatments was similar to the raw wastewater and the oxidation ditch wastewater from a treatment plant. We also found that the ECPPs with polymeric iron sulfate had the smallest effect on the microbial community. In practical applications, these findings provide a reference for an established link between the physicochemical and biochemical treatment of PDW.

Pretreatment of printing and dyeing wastewater by Fe/C micro-electrolysis combined with H2O2 process.

A novel iron-carbon (Fe/C) micro-electrolysis combined with H2O2 (ICMH) process was proposed to pretreat the printing and dyeing wastewater (PDW), using a micro-electrolysis filling. The effects of H2O2 concentration, reaction time, initial pH, and Fe/C dosage on chemical oxygen demand (COD) removal rate of PDW were optimized by response surface methodology (RSM). The maximum COD removal rate was approximately 77.65% after 186 min treatment, when the concentration of H2O2, initial pH and the dosage of Fe/C were 8.88 g/L, 1.5 and 837 g/L, respectively. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2 = 0.9780). And H2O2 concentration and initial pH were the key factors to improve the treatment effect. UV-Vis spectra indicated that a significant blue shift at 220 nm, attributing that fused aromatic hydrocarbons were degraded effectively. 3D-EEM spectra analysis showed that the water samples of PDW mainly contained three kinds of organic matter: refractory fulvic acid, soluble microbial metabolites and aromatic proteins, and the degradation rate of these was 81.76%, 53.78% and 70.83%, respectively.

Manipulating catalytic activity and durability of Pt-modified Cu–Fe–La/γ-Al2O3 ternary catalyst for catalytic wet air oxidation: effect of calcination temperature

A series of novel Pt-modified Cu–Fe–La/γ-Al2O3 catalysts were prepared by an incipient-wetness impregnation method, and their performances were evaluated in catalytic wet air oxidation (CWAO) of printing and dyeing wastewater (PDW).