Removal of color from textile dyeing wastewater by foam separation

Application of novel continuous foam collection methods for removal of PFAS from cascade generated foam at wastewater treatment plants

Three foam collection methods - passive overflow, mesh skimmer, and mesh-belt skimmer - were iteratively designed and evaluated for continuous collection of foam forming at a wastewater treatment plant (WWTP) cascade for removal of per- and polyfluorinated alkyl substances (PFAS). Surface tension, PFAS concentrations, and foamate collection rates were measured to assess their performance. Foam collection using a novel mesh skimmer and mesh-belt skimmer increased PFAS enrichment over that of the in situ foam, as the mesh facilitated drainage of PFAS-depleted liquid during collection. Enhanced enrichment and scalable foam collection with the mesh-belt skimmer may remove and concentrate most long-chain PFAS (>90 %) in under 270,000 L/d of foamate or 0.26 % of the wastewater volume when scaled up. For comparison, an estimated 900,000 L/d of foamate would need to be collected with the passive overflow method to achieve 90 % PFOS removal, but would only capture 20 % PFOA and 22 % PFHxS. Limiting the volume of final collected foamate is critical as it requires additional treatment, which can be cost prohibitive at large volumes. While a pilot scale study is required to accurately assess removal, the advantages provided by the mesh-belt skimmer suggest feasible foam collection for PFAS removal at the full WWTP scale.

Smart Bacterial Cellulose-Methylacrylated Chitosan Composite Hydrogel: Multifunctional Characterization for Real-Time pH Monitoring

pH is a critical parameter that influences biochemical and environmental processes. Real-time and accurate pH detection is essential for monitoring health and the environment. Herein, a bacterial cellulose and methylacrylated chitosan (BC-MACS) composite hydrogel was prepared to achieve rapid pH detection. The integration of MACS reduced the crystallinity of pristine BC, with no adverse effects on thermal stability. SEM images validated the fibrous nature of the BC-MACS composite, indicating that MACS was successfully infiltrated into the pores of BC. By incorporating MACS into the BC matrix, the exceptional biocompatibility of BC was maintained, while simultaneously augmenting its mechanical properties. Due to the excellent swelling ability of MACS, the fabricated BC-MACS hydrogel exhibited superior swelling behavior compared to the BC hydrogel, which facilitated the absorption of the solution under test. A BC-MACS pH sensor was fabricated by introducing the pH indicator solution, and the color variation across the pH range (2-12) demonstrated a clear response to pH changes. Therefore, the BC-MACS pH sensor holds potential for use as a visual indicator in a diverse range of applications, especially for health and environmental monitoring.

A novel strategy by combining foam fractionation with high-speed countercurrent chromatography for the rapid and efficient isolation of antioxidants and cytostatics from Camellia oleifera cake

Camellia oleifera cake is a by-product, which is rich in functional chemical components. However, it is typically used as animal feed with no commercial value. The purpose of this study was to isolate and identify compounds from Camellia oleifera cake using a combination of foam fractionation and high-speed countercurrent chromatography (HSCCC) and to investigate their biological activities. Foam fractionation with enhanced drainage through a hollow regular decahedron (HRD) was first established for simultaneously enriching flavonoid glycosides and saponins for further separation of target compounds. Under suitable operating conditions, the introduction of HRD resulted in a threefold increase in enrichment ratio with no negative effect on recovery. A novel elution-extrusion countercurrent chromatography (EECCC) coupled with the consecutive injection mode was established for the successful simultaneous isolation of flavonoid glycosides and saponins. As a result, 38.7 mg of kaemferol-3-O-[2-O-D-glucopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside (purity of 98.17%, FI), 70.8 mg of kaemferol-3-O-[2-O-β-D-xylopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside (purity of 97.52%, FII), and 560 mg of an oleanane-type saponin (purity of 92.32%, FIII) were separated from the sample (900 mg). The present study clearly showed that FI and II were natural antioxidants (IC50 < 35 μg/mL) without hemolytic effect. FIII displayed the effect of inhibiting Hela cell proliferation (IC50 < 30 μg/mL). Further erythrocyte experiments showed that this correlated with the extremely strong hemolytic effect of FIII. Overall, this study offers a potential strategy for efficient and green isolation of natural products, and is beneficial to further expanding the application of by-products (Camellia oleifera cake) in food, cosmetics, and pharmacy.

Hydrothermal Alkaline Treatment (HALT) of Foam Fractionation Concentrate Derived from PFAS-Contaminated Groundwater

While foam fractionation (FF) process has emerged as a promising technology for removal of per- and polyfluoroalkyl substances (PFASs) from contaminated groundwater, management of the resulting foam concentrates with elevated concentrations of PFASs (e.g., >1 g/L) remains a challenge. Here, we applied hydrothermal alkaline treatment (HALT) to two foam concentrates derived from FF field demonstration projects that treated aqueous film-forming foam (AFFF)-impacted groundwater. Results showed >90% degradation and defluorination within 90 min of treatment (350 °C, 1 M NaOH) of all 62 PFASs (including cations, anions, and zwitterions) identified in foam concentrates. Observed rate constants for degradation of individual perfluoroalkyl sulfonates (PFSAs, CnF2n+1-SO3-), the most recalcitrant class of PFASs, in both foam concentrates were similar to values measured previously in other aqueous matrices, indicating that elevated initial PFAS concentrations (e.g., PFHxSinit = 0.55 g/L), dissolved organic carbon (DOC; up to 4.5 g/L), and salt levels (e.g., up to 325 mg/L chloride) do not significantly affect PFAS reaction kinetics. DOC was partially mineralized by treatment, but a fraction (∼15%) was recalcitrant. Spectroscopic characterization revealed molecular features of the HALT-recalcitrant DOC fraction, and nontarget high-resolution mass spectrometry tentatively identified 129 nonfluorinated HALT-recalcitrant molecules. Analysis of process energy requirements shows that treating PFAS-contaminated foam concentrates with HALT would add minimally (<5%) to the overall energy requirements of an integrated FF-HALT treatment train.

Treatment of Olefin plant spent caustic by combination of Fenton-like and foam fractionation methods in a bench scale

Spent Merox caustic (SMC) is a hazardous waste that is produced during the Merox desulfurization process in the petroleum refinery industry and should be treated before discharging to environment. In the present study, treatment of SMC was investigated by three methods including Fenton-like process, foam fractionation, and a combination of both processes. Immobilized TiO₂/Fe⁰ on modified silica nanoparticles was used as a heterogeneous Fenton-like catalyst. The chemical and physical characteristics of the catalyst were determined using Fourier-transform infrared spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and transmission electron microscopy techniques. The treatment performance of the combined method was measured as a cost-effective method with chemical oxygen demand (COD) removal percentage. The effect of parameters including pH, gas flow rate, surfactant type and concentration of hydrogen peroxide, catalyst, and chelate were investigated. It is found that the prepared heterogeneous catalyst has high activity for the treatment of SMC. In addition, the results showed that the combined method achieved 97.6 ± 0.5% COD removal, while the measured values for Fenton or foam fractionation methods alone did not exceed 85.5 ± 1% and 47.2 ± 0.4%, respectively. The advantage of combination process over foam fractionation was the use of an advanced oxidation process in the separating column to eliminate or reduce the secondary phase contamination load. Besides, the role of the column in the effective contact of contaminants with the rising bubbles improved the degradation performance of the proposed process and reduced the consumption of hydrogen peroxide by 46% compared to the Fenton-like method.

Foam drainage enhancement in foam fractionation for dye removal: process optimization by Taguchi methodology and grey relational analysis

The isolation of dye (methylene blue) by employing a foam fractionation technique with the assistance of a surfactant (sodium dodecyl sulfate) has been dealt with in this paper. This study also incorporated the comparison between contrasted and experimental columns. Taguchi methodology and grey relational analysis techniques were used to ascertain optimal conditions at which the column should be operated to achieve maximum percentage removal and enrichment ratio, for both the columns. The analysis of variance study suggested dye concentration to be the most influencing parameter. The relationship between dye concentration in the bulk phase and the foam phase was also deduced.

Removal of color from real textile dyeing effluent utilizing tannin immobilized jute fiber as biosorbent: optimization with response surface methodology

The present study explored an efficient technoeconomic method for treating intensely colored dyeing effluents from a commercial source. Firstly, the adsorption efficacy of jute fiber (JF) was enhanced through grafting with tannin, a natural polyphenol, via incorporation of active epoxy groups by epichlorohydrin onto fiber surface. The effect of different experimental parameters (e.g., initial pH, adsorbent dose, temperature, and contact time) on extent of color removal was evaluated performing batch studies. A full factorial central composite design (CCD) in response surface methodology (RSM) was applied to optimize the decolorization process for achieving maximum color removal (99.5%) at pH 4.9, adsorbent dose 11.8 g/L, temperature 30 °C, and time of contact 117.8 min. The isotherm and kinetic studies of the process revealed that Langmuir model and pseudo-second-order model provided best fit, yielding high correlation coefficients (R² > 0.997). Significant desorption (76%) of the spent adsorbent by 0.1 M NaOH solution suggested that this tannin-modified JF can find a prospective practical application as a novel, inexpensive, and potential bioadsorbent to treat the dyeing effluent.

Bacterial cellulose-based re-swellable hydrogel: Facile preparation and its potential application as colorimetric sensor of sweat pH and glucose

Direct deposition of the negatively charged polyelectrolyte, carboxymethyl cellulose (CMC), into a bacterial cellulose (BC) matrix was used as a simple route to fabricate a re-swellable and biocompatible cellulose-based hydrogel. As a result of this non-destructive approach, the physical and mechanical property of the original BC were well-preserved within the resulting BC/CMC hydrogel. As a BC/CMC-based colorimetric pH sensor, it exhibited a rapid response with an easy color differentiation between each pH by the naked eye, and wide linear range of pH 4.0-9.0 with good linearity. For the detection of glucose in sweat, the BC/CMC-based colorimetric glucose sensor provided a low limit of detection (25 μM) with a wide linear detection range (0.0-0.5 mM) and high accuracy. These BC/CMC based sensors could potentially be applied as non-invasive semi-quantitative sensors for on-skin health monitoring.

Recycling Iron-Containing Sludges from the Electroflocculation of Printing and Dyeing Wastewater into Anode Materials for Lithium-Ion Batteries

Iron-containing sludges (DW/Fe) were prepared by the electroflocculation of industrial printing and dyeing wastewater (DW). To investigate the formation process and the properties of the DW/Fe sludges and their application in anode materials in Li-ion batteries, the DW/Fe sludges were compared to three other sludges (MB/Fe, RB/Fe, Ta/Fe) prepared from model solutions that contained either methyl blue (MB), rhodamine B (RB), or tartrazine (Ta). The DW/Fe sludges were calcined at 500 °C under N₂ to form iron oxide/carbon composite C-DW/Fe. The composition and structure of the sludges and the C-DW/Fe composite were analyzed by using FTIR spectroscopy, XRD, thermogravimetric analysis, SEM, TEM, and X-ray photoelectron spectroscopy, and their performances as anodes of Li-ion batteries were studied by adding different proportions of conductive agent (super P® conductive carbon black). Our results show that the sludges are a complex mixture of Fe₃ O₄ and organic matter. The specific capacity and stability can be improved during the charge-discharge test by increasing the amount of carbon black. Importantly, this improvement is more pronounced on DW/Fe that does not require high-temperature carbonization, which means that the sludges cannot only protect the environment and avoid the waste of resources but also can be used directly and widely in decentralized energy storage devices.

Foam Separation of Dyes Using Anionic, Cationic, and Amphoteric Surfactants

Foam separation can selectively remove a target substance from a solution via adsorption of the substance with the surfactant at the surface of the bubble. A cationic dye, methylene blue, and an anionic dye, Fast Green FCF, were prepared as substances to be removed via foam separation. Anionic (sodium dodecyl sulfate, SDS), cationic (dodecyltrimethylammonium chloride, DTAC), and amphoteric (3-(dodecyldimethylammonio)propane-1-sulfonate, SB-12) surfactants were used in the foam separation process. The effectiveness of the surfactants for removing the cationic methylene blue increased as follows: DTAC < SB-12 < SDS. On the other hand, the effectiveness of the surfactants for removing the anionic Fast Green FCF was in the opposite order. The dyes were effectively adsorbed by the foams via electrostatic interactions between the oppositely charged surfactant and the dye molecules. Since amphoteric surfactants have both anionic and cationic charges in a molecule, they could effectively remove both dyes in the foam separation process. Therefore, it was found that the amphoteric surfactant was highly versatile. Analysis of the kinetics of the removal rate showed that the aqueous solutions of monomers could remove the dyes more effectively than micellar solutions in foam separation.

Porous composite architecture bestows Fe-based glassy alloy with high and ultra-durable degradation activity in decomposing azo dye

Since the treatment of wastewater containing azo dye presents problems worldwide, it is important to seek effective materials and technology for the purification of wastewater containing azo dye. Fe-based metallic glasses have been identified as promising materials for the decomposition of dyeing wastewater due to their high chemical activity resulting from their amorphous structure. It is imperative to further improve their degradation performance, and especially their durability, for potential application in wastewater purification. Here, composite structures constructed of porous Ni and amorphous Fe₇₈Si₉B₁₃ powder with markedly enhanced degradation performance in Orange II solution were obtained by utilizing a magnet. Due to the favorable effects of structural electrocatalysis and high dispersity of the distinctive porous architecture in addition to its self-cleaning properties, the solid-liquid interface exhibited strong, continuous electrical and mass transport, and a compelling improvement in degradation performance was achieved. Based on degradation tests and spectrum analysis, the kinetic rate was improved over 11-fold. Moreover, ultra-high durability over 100 cycles was revealed in cycling tests. The results indicate that wastewater degradation performance can be greatly enhanced by properly combining Fe-based metallic glasses with porous material.

Iron Oxide/Chitosan Magnetic Nanocomposite Immobilized Manganese Peroxidase for Decolorization of Textile Wastewater

Because of its effectiveness in organic pollutant degradation, manganese peroxidase (MnP) enzyme has attracted significant attention in recent years regarding its use for wastewater treatment. Herein, MnP was extracted from Anthracophyllum discolor fungi and immobilized on the surface of magnetic nanocomposite Fe3O4/chitosan. The prepared nanocomposite offered a high surface area for MnP immobilization. The influence of several environmental factors like temperature, pH, as well as storage duration on the activity of the extracted enzyme has been studied. Fourier transmission infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM) techniques were used for the characterization of the prepared MnP/Fe3O4/chitosan nanocomposite. The efficiencies of the prepared MnP/Fe3O4/chitosan nanocomposite for the elimination of reactive orange 16 (RO 16) and methylene blue (MB) industrial dyes were determined. According to the results, the immobilization of MnP on Fe3O4/chitosan nanocomposite increases its capacity to decolorize MB and RO 16. This nanocomposite allowed the removal of 96% ± 2% and 98% ± 2% of MB and RO 16, respectively. The reusability of the synthesized nanocomposite was studied for five successive cycles showing the ability to retain its efficiency even after five cycles. Thus, the prepared MnP/Fe3O4/chitosan nanocomposite has potential to be a promising material for textile wastewater bioremediation.

Nonspontaneous and multilayer adsorption of malachite green dye by Acacia nilotica waste with dominance of physisorption

Adsorption of the hazardous dye malachite green (MG) by Acacia nilotica (AN) waste was investigated. Batch process variables for the adsorption of MG by AN were optimized. The mechanisms involved in the adsorption of MG by AN were explored using isotherms and kinetic models. The thermodynamic parameters were calculated to determine the spontaneity and thermal nature of the MG adsorption reaction. The maximum equilibrium adsorption capacity of AN was found to be 113.26 mg/g at 30 °C. The MG adsorption data revealed that AN adsorbs MG by multilayer adsorption, as shown by the better fit of the data to the Freundlich and Halsey models (R² = 0.99) rather than to the Langmuir model. Multilayer adsorption involves physisorption, which was confirmed by the E value (mean free energy of adsorption) of the Dubinin-Radushkevich model (6.52 kJ/mol). Surface diffusion was found to be the main driving force for MG adsorption by AN. The MG adsorption reaction was endothermic, based on the enthalpy, and was controlled by the entropy of the system in the T₁ temperature range (30 to 40 °C), while the opposite trend was observed in the T₂ range (40 to 50 °C). Moreover, MG adsorption by AN was found to be nonspontaneous at all temperatures.

Microscopic Evidence for the Correlation of Micellar Structures and Counterion Binding Constant for Flexible Nanoparticle Catalyzed Piperidinolysis of PS− in Colloidal System

The interest to determine the ionization degree of counterion initiates the need to study the relationship between counterion binding constant (RX Br) and the growth of self-assembly micellar structure. This paper discussed the microscopic evidence for the correlation of counterion binding constant values and micellar structure of cationic surfactants in the presence of phenolates and 2-ethyl phenolates ions in flexible nanoparticle (FN)-system of ionized phenyl salicylate-catalyzed piperidinolysis. The sizes of micelles were determined by particle size analysis. Transmission electron microscopy (TEM) results showed a spherical micellar structure for phenolates and 2-ethyl phenolates ions at counterion binding constant values 6.3 ± 1.0 and 24.0 ± 1.1 respectively. A study using a semi-emperical kinetic technique in published article proved that the suggested micellar structures at respective counterion binding constant values corresponded with the present microscopic evidence.

Mild-Vectolysis: A Nondestructive DNA Extraction Method for Vouchering Sand Flies and Mosquitoes

Nondestructive techniques allow the isolation of genomic DNA, without damaging the morphological features of the specimens. Though such techniques are available for numerous insect groups, they have not been applied to any member of the medically important families of mosquitoes (Diptera: Culicidae) and phlebotomine sand flies (Diptera: Psychodidae). This study presents Mild-Vectolysis, the first nondestructive DNA extraction methodology for vouchering taxa of mosquitoes and sand flies, which provided sufficient amounts of DNA, tested in a verified barcode (cytochrome oxidase I gene), while preserving their morphological integrity. Application of the method to sand flies allowed successful insect identification post DNA extraction, as all basic taxonomical structures necessary for identification (pharynx, cybarium, and genitalia) remained intact. The development of the methodology was more challenging in mosquitoes, due to the fragility of key morphological characters (scales and color). A small modification of the lysis buffer concentration, in combination with the adjustment of the incubation time, a postlysis freezing stage, and the avoidance of ethanol, achieved the extraction of sufficient DNA quantity, while preserving the integument of the mosquitoes, although a small proportion of the scales and the color still appeared to have been lost. In addition to the practicality and efficiency of our methodology, preserving of the original insect specimen post DNA extraction is highly advantageous, as it allows for 1) utilization of the specimen for further analysis and 2) storage for vouchering.

Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes

Release of textile azo dyes to the environment is an issue of health concern while the use of microorganisms has proved to be the best option for remediation. Thus, in the present study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes. The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h at 100 mg L^-1 concentration at 30 ± 0.2 °C under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes. However, decolorization under microaerophilic conditions viz. RB 5 (0.26 mM), RO 16 (0.18 mM), DR 78 (0.20 mM) and DR 81 (0.23 mM) and sequential aerobic/microaerophilic processes viz. RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines. In distinction, sequential microaerophilic/ aerobic process doesn’t show the formation of amines. Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes. Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines. Also, the acute toxicity assay with Daphnia magna revealed the nontoxic nature of the dye-degraded metabolites under sequential microaerophilic/aerobic processes. As biodegradation under sequential microaerophilic/aerobic process completely detoxified all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies.

Low-Cost Biodegradation and Detoxification of Textile Azo Dye C.I. Reactive Blue 172 byProvidencia rettgeriStrain HSL1

Present study focuses on exploitation of agricultural waste wheat bran (WB) as growth medium for degradation of textile azo dye C.I. Reactive Blue 172 (RB 172) using a single bacteriumP. rettgeristrain HSL1 (GenBank accession numberJX853768.1). The bacterium was found to completely decolorize 50 mg L−1of dye RB 172 within 20 h at 30 ± 0.2°C under microaerophilic incubation conditions. Additionally, significant reduction in COD (85%) and TOC (52%) contents of dye decolorized medium was observed which suggested its mineralization. Induction in the activities of azoreductase (159%) and NADH-DCIP reductase (88%) provided an evidence for reductive cleavage of dye RB 172. The HPLC, FTIR, and GC-MS analysis of decolorized products confirmed the degradation of dye into various metabolites. The proposed metabolic pathway for biodegradation of RB 172 has been elucidated which showed the formation of 2 intermediate metabolites, namely, 4-(ethenylsulfonyl) aniline and 1-amino-1-(4-aminophenyl) propan-2-one. The acute and phytotoxicity evaluation of degraded metabolites suggests that bacterial strain favors the detoxification of dye RB 172. Thus, WB could be utilized as a low-cost growth medium for the enrichment of bacteria and their further use for biodegradation of azo dyes and its derivatives containing wastes into nontoxic form.