Initial Dye Concentration Research Articles

Biodegradation of aniline blue dye by salt-tolerant Bacillus thuringiensis DHC4 isolated from soil-feeding termite guts

The existence of aniline blue in aquatic environments poses a large threat to aquatic organisms. Microbial degradation of aniline blue has been frequently used in remediation because of its effectiveness, low cost, and environmental friendliness. However, the mechanisms by which the dye can be biodegraded are not well understood. In this study, Bacillus thuringiensis DHC4 was isolated from the gut of a soil-feeding termite, and its ability to degrade aniline blue was investigated. The results showed that DHC4 was highly resistant to both aniline blue and salt, with the decolorization rate reaching 78% and 67% after 96 h of incubation at initial dye concentrations of 1 g/L and 7% salinity, respectively. Aniline blue degradation products were identified based on UV–vis, FTIR, and GC–MS analyses, and genome analysis confirmed that DHC4 contained many potential dye-degrading genes. Transcriptome analysis revealed significant up-regulation of methyltransferase, nitroreductase, arylamine N-acetyltransferase and oxidoreductase genes on exposure to aniline blue, indicating their active role in its biodegradation. A new degradation pathway of aniline blue by DHC4 is proposed, based on analysis of metabolites and differentially expressed genes. This mechanism involves cleavage of aniline blue by oxidoreductases into mono- and diphenyl ring molecules, followed by further methylation and alkylation through methyltransferases. The phytotoxicity results showed that aniline blue was degraded by DHC4 into less toxic metabolites. These results provide new insights into the mechanism of biodegradation of aniline blue by microorganisms.

Enhanced adsorption of Bismark Brown R dye by chitosan conjugated magnetic pectin loaded filter mud: A comprehensive study on modeling and mechanisms

Herein, a polymer-based bioadsorbent was prepared by cross-linking chitosan to filter mud and magnetic pectin (Ch-mPC@FM) for the removal of Bismark Brown R dye (BB-R) from wastewater. Morphological characterization analysis indicated that Ch-mPC@FM had a higher surface area and better pore structure than its components. The Artificial Neuron Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) were employed to evaluate the simulation and prediction of the adsorption process based on input variables like temperature, pH, dosage, initial BB-R dye concentration, and contact time. ANFIS and ANN demonstrated significant modeling and predictive accuracy, with R2 > 0.93 and R2 > 0.96, and root mean square error < 0.023 and <0.020, respectively. The Langmuir isotherm and the pseudo-second-order kinetic models provided the best fits to the equilibrium and kinetic data. The thermodynamic assessment showed spontaneous and endothermic adsorption with average entropy and enthalpy changes of 119.32 kJ mol−1 K and 403.47 kJ mol−1, respectively. The study of BB-R dye adsorption on Ch-mPC@FM revealed multiple mechanisms, including electrostatic, complexation, pore filling, cation-π interaction, hydrogen bonding, and π-π interactions. The approximate production cost of US$ 5.809 Kg−1 and excellent adsorption capability render Ch-mPC@FM an inexpensive, pragmatic, and ecologically safe bioadsorbent for BB-R dye removal from wastewater.

Sustainable Chitosan Supported Magnetite Nanocomposites for Sequestration of Rhodamine B Dye from the Environment

This study investigated the sustainable chitosan supported magnetite nanocomposites (C-Fe3O4) for sequestration of Rhodamine B (RhB) Dye from environment. The synthesis of C-Fe3O4, its physicochemical characterization and synergistic influence of initial concentration of the dye and time of contact with the adsorbent during the sorption of Rhodamine B (RhB) on C-Fe3O4 were studied. The physicochemical properties indicated better equilibration via bulk density of 0.731 g/cm3, moisture content 7.2, point of zero charge (PZC) of 4 indicated suitability for RhB. Functional group of C-Fe3O4 determined by FTIR revealed characteristics peaks at 3433 cm−1 and 698 – 478 cm−1 confirming the successful formation by incorporation of chitosan and magnetite nanoparticles. Synergistic influence of the time of contact and initial concentration of Rb dye influenced the dye sorption. Effective adsorption of RhB onto C-Fe3O4 was studied using batch adsorption techniques at initial concentration (200 – 1000 ppm), contact time (10 – 120 min), stirring speed (120 rpm), temperature of 25 °C and adsorbent dosage of 100 mg. Rapid adsorption of RhB onto C-Fe3O4 was obtained at 10 min with 96.9% removal efficiency at highest RhB concentration of 1000 ppm. The study revealed the efficacy of contact time and initial dye concentration as imperative operational parameters majorly influencing sorption study.

Advancements in application of modified biochar as a green and low-cost adsorbent for wastewater remediation from organic dyes.

Synthetic organic dyes, which are resistant to biodegradation, pose a notable health risk, potentially leading to cancer and respiratory infections. Researchers have addressed this concern by exploring physicochemical methods to remove organic dyes from wastewater. A particularly promising solution involves modified biochar adsorbents, which demonstrate high efficiency in organic dye removal. Biochar, a charcoal-like material derived from biomass pyrolysis, offers advantages such as low cost, eco-friendliness, high efficiency and reusability. Beyond its role in sustainable soil remediation, biochar proves effective in removing organic dyes from wastewater after undergoing physical or chemical modification. Acid-base activation or metal-heteroatom impregnation enhances biochar's adsorption capacity. This comprehensive review examines the attributes of biochar, common methods for production and modification, and the impacts of raw materials, pyrolysis temperature, heating rate and residence time. It further elucidates the biochar adsorption mechanism in the removal of organic dyes, assessing factors influencing efficiency, including biochar feedstock, solution pH, adsorption temperature, particle size, initial dye concentration, biochar dosage and reaction time. It explores challenges, opportunities, reusability and regeneration methods of biochar in treating organic dye wastewater. It also discusses recent advances in organic dye removal using adsorption-based biochar. The review ultimately advocates for enhancing biochar's adsorption performance through post-modification.

Exploring the potential of olive pomace derived activated charcoal as an efficient adsorbent for methylene blue dye: a comprehensive investigation of isotherms, kinetics, and thermodynamics

Methylene blue (MB) is a heterocyclic aromatic chemical compound used as a dye in various dyeing processes. The accumulation of such an organic compound poses a significant threat to both the environment and human health. Therefore, numerous biological, physical, and chemical processes have been established to remove MB dye, with adsorption being the most predominant dye-based treatment technology. In this context, the aim of this work was to evaluate the adsorption properties of activated carbon derived from olive pomace against methylene blue. To this end, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out to confirm the adsorption of MB on carbon structures. In addition, the effect of contact time, pH, initial dye concentration, adsorbent dose, and temperature on the adsorption efficiency of MB was investigated. On the other hand, kinetic and isothermal models were used to further understand the adsorption mechanism, which showed a good correlation with the pseudo-second-order kinetic model and the Langmuir isotherm. Finally, thermodynamic analysis showed favorable conditions for physisorption, with the process being both endothermic and spontaneous.

Superior decomposition of xenobiotic RB5 dye using three-dimensional electrochemical treatment: Response surface methodology modelling, artificial intelligence, and machine learning-based optimisation approaches

The highly efficient electrochemical treatment technology for dye-polluted wastewater is one of hot research topics in industrial wastewater treatment. This study reported a three-dimensional electrochemical treatment process integrating graphite intercalation compound (GIC) adsorption, direct anodic oxidation, and ·OH oxidation for decolourising Reactive Black 5 (RB5) from aqueous solutions. The electrochemical process was optimised using the novel progressive central composite design–response surface methodology (CCD–NPRSM), hybrid artificial neural network–extreme gradient boosting (hybrid ANN–XGBoost), and classification and regression trees (CART). CCD–NPRSM and hybrid ANN–XGBoost were employed to minimise errors in evaluating the electrochemical process involving three manipulated operational parameters: current density, electrolysis (treatment) time, and initial dye concentration. The optimised decolourisation efficiencies were 99.30%, 96.63%, and 99.14% for CCD–NPRSM, hybrid ANN–XGBoost, and CART, respectively, compared to the 98.46% RB5 removal rate observed experimentally under optimum conditions: approximately 20 mA/cm2 of current density, 20 min of electrolysis time, and 65 mg/L of RB5. The optimised mineralisation efficiencies ranged between 89% and 92% for different models based on total organic carbon (TOC). Experimental studies confirmed that the predictive efficiency of optimised models ranked in the descending order of hybrid ANN–XGBoost, CCD–NPRSM, and CART. Model validation using analysis of variance (ANOVA) revealed that hybrid ANN–XGBoost had a mean squared error (MSE) and a coefficient of determination (R2) of approximately 0.014 and 0.998, respectively, for the RB5 removal efficiency, outperforming CCD–NPRSM with MSE and R2 of 0.518 and 0.998, respectively. Overall, the hybrid ANN–XGBoost approach is the most feasible technique for assessing the electrochemical treatment efficiency in RB5 dye wastewater decolourisation.

Adsorption of the Color Pollutant onto NiO Nanoparticles Prepared by a New Green Method

Green synthesis methods have emerged as favorable techniques for the synthesis of nano-oxides due to their simplicity, cost-effectiveness, eco-friendliness, and non-toxicity. In this study, Nickel oxide nanoparticles (NiO-NPs) were synthesized using the aqueous extract of Laurus nobilis leaves as a natural capping agent. The synthesized NiO-NPs were employed as an adsorbent for the removal of Biebrich Scarlet (BS) dye from aqueous solution using adsorption technique. Comprehensive characterization of NiO-NPs was performed using various techniques such as atomic force microscopy (AFM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett and Teller (BET) analysis, and scanning electron microscopy (SEM). Additionally, operational parameters including adsorbent weight, adsorption duration, temperature, pH value, and initial BS dye concentration were optimized for the adsorption process. Isotherm analysis indicated a better fit of the Langmuir model with equilibrium experimental data than the Freundlich model. The kinetic study revealed that the Pseudo-second-order (PSO) model was more suitable to represent the adsorption process compared to the Pseudo-first-order (PFO) kinetic model. Thermodynamic analysis encompassing the changes in Gibbs free energy (∆G˚), enthalpy (∆H˚), and entropy (∆S˚) unveiled that the adsorption of BS dye onto NiO-NPs was a spontaneous endothermic process with an increase in the randomness.

Decolourization of Methylene Blue by using Eucalyptus Globulus Leaf Powder as a Adsorbent

In the present study, the feasibility of using low-cost adsorbent Eucalyptus Globulus leaf powder for the cationic dyes adsorption from aqueous solutions have been investigated. Batch adsorption studies are conducted to study conducted to the different parameters are adsorbent dosage of 2-20 g/L, initial dye concentration of 50-250 mg /L, Temperature of 293oK, 303 oK and 313 oK on adsorption of methylene blue dye at equilibrium time of 80 minutes respectively and optimal pH of 5.0. The equilibrium data is analysed with isotherm models are Langmuir and Freundlich and kinetic models are Pseudo-first order, Pseudo-second order model. The adsorption equilibrium and kinetic data fitted well to Freundlich isotherm model for methylene blue dye and Pseudo-second order model for methylene blue dyes. The adsorption is an Endothermic and it is energetically favourable adsorption. The result demonstrates that Eucalyptus Globulus leaf powder could be employed as effective and low-cost adsorbent for the removal of methylene blue and from aqueous solutions.

Adsorption, kinetics, and thermodynamic study of dyeing the Scutellaria Orientalis L as an eco-friendly natural colourant on cotton fabric

The adsorption isotherm, thermodynamic parameter, and kinetics study for dyeing without mordanting cotton fabric dyed with natural dye obtained from an aqueous extract of the Scutellaria Orientalis were investigated using, as optimal conditions, at pH of 5 a material to liquor ratio (MLR) of 1:100, an initial dye concentration of 1.0/l and contact time (20–90 min.). The effect of the temperature and dyeing time (from 20–90 min.) on dyeing was evaluated using three different temperatures (from 60, 80, and 90°C). Also, the adsorption isotherms have been analyzed by Langmuir and Freundlich models. It is revealed that the adsorption kinetics was found to follow the pseudo-first-order kinetic model, the obtained adsorption isotherm was found to be suitable for both Langmuir and Freunlich adsorption isotherm, and the dyeing process is exothermic. The rate of dye uptake and thermodynamic parameters have also been calculated and discussed.

Polypyrrole-encapsulated metal oxide nanocomposite for adsorptive abatement of anionic dye from dye laden wastewater: Cost analysis and scale up design

The present work demonstrates the fabrication of an organometallic material i.e. polypyrrole-encapsulated zinc oxide (PPy@ZnO) nanocomposite for adsorptive elimination of Eriochrome black-T (EBT) dye from water. The specific surface area and pore volume of the PPy@ZnO nanocomposite were observed to be 28.726 m2/g and 0.086 cc/g, respectively. At optimum experimental conditions of solution pH; 4.0, PPy@ZnO nanocomposite dose: 1.0 g/L, contact time: 30 min and initial EBT dye concentration: 50 mg/L, maximum EBT dye removal efficiency of ∼94±1.86% was obtained. The pseudo-second-order kinetic and Langmuir isotherm model provides the best fit for the adsorption experiments, with maximum EBT dye adsorption capacity of 277.78 mg/g. The prominent adsorption mechanisms include the hydrogen bonding, π–π interactions, and electrostatic attraction. The adsorption study is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0, ΔS° > 0) in nature as indicated by the thermodynamics study. The reduction in EBT dye removal efficiency was insignificant (∼10±0.94%) in surface water as compared to other real water samples. Monovalent anions (i.e., NO3–and Cl–) have minimal impact on EBT removal efficiency with reduction in removal efficiencies in the range of 4.0±1.54% to ∼11.0±1.93%. Regeneration study suggests an overall ∼20±1.45% decrease in the EBT dye removal efficiency after 5th cycle of regeneration. Response surface methodology suggests the maximum adsorption efficacy of 95±1.68% at initial EBT dye concentration of 35 mg/L, PPy@ZnO dose of 0.85 g/L and contact time of 40 min. The estimated synthesis cost of PPy@ZnO nanocomposite was determined to be ∼117 USD/kg. Batch mode scale-up design suggests a minimum of 87.48 g of PPy@ZnO nanocomposite needs to be applied to treat 50 mg/L of EBT dye loaded wastewater (50 L volume) with 95% dye removal efficiency.

Bioremediation of Wastewater Contaminated with Dyes, Rhodamine B Using Alginate Immobilized Cell of Spirulina platensis

Bioremediation of wastewater contaminated with rhodamine B dyes using alginate immobilized cell of Spirulina platensis was studied. Factors affecting the dye adsorption such as pH, contact time, adsorbent dose, and initial dye concentration were investigated. The results showed that the optimum pH for dye adsorption was at 2 with an adsorption capacity of 0.86±0.00 mg/g. The adsorption was very rapid and reached equilibrium within 180 min with an adsorption capacity of 1.24±0.00 mg/g. Dye adsorption capacity by this alga was reduced at high adsorbent dose whereas the increase of initial concentration of dye increased the adsorption capacity. The adsorption isotherm correlated with Langmuir with the maximum adsorption capacity (qm) of 52.70±3.18 mg/g. Adsorption kinetic correlated with pseudo-second order. The adsorption rate limiting step were film diffusion rate and secondary rate of intraparticle diffusion. This study suggested that alginate immobilized cell of S. platensis can be applied for treatment of wastewater contaminated with rhodamine B.

Physicochemical interaction of microstructured drumsticks with synthetic Dye: The tailoring of surface phenomenon

The current study shows that drumstick powder is a potential adsorbent to remove Congo Red from synthetic wastewater by a batch technique. CR as a textile waste harms the ecology and the water ecosystem, and it should be removed from WW. At various experimental conditions, various operating parameters such as initial concentration of dye (25–300 ppm), contact time (10–240 mins), pH (1–12) and adsorbent dosage (0.1–1.0 g/L) were investigated. The reaction kinetics and adsorption isotherms were examined. Maximum removal of dye has been found at pH 2. Dye concentration is an important factor and it is inversely related to the percentage removal. 100 ppm was chosen as the IC for the optimization experiment. Increasing the amount of adsorbent dosage and contact time, there is an rise in the percentage removal of dye particles. The optimum adsorbent dosage was found 0.5 g/L and the contact time 90 mins. The maximum adsorption capacity has been found to be 114.94 mg/g. The adsorption mechanism closely matched the Freundlich isotherm and pseudo-second-order kinetic models.

Facile one step microwave assisted biofabrication of Fe2O3 NPs: potential application as solar light-driven photocatalyst in the photodegradation of acridine orange

ABSTRACT The utilisation of a recently developed green approach for synthesising iron oxide nanoparticles (Fe2O3NPs) is highly promising, given its low toxicity and environmentally benevolent attributes. In this investigation, Fe2O3 NPs were produced through the utilisation of ferric chloride hexahydrate, incorporating Permelia perleta ;(lichen) extract under standard atmospheric conditions. The development of Fe2O3 NPs was verified through a systematic characterization process by employing UV FTIR, XRD, and FE SEM studies. The average crystallite size of the developed sample was found to be 20 nm determined by using Debye – Scherrer equation. The efficacy of the developed Fe2O3 NPs as a photocatalyst in eliminating acridine orange was evaluated, highlighting key factors such as catalyst dosage, initial dye concentration, and pH. Augmenting the quantity of Fe2O3 NPs amplified the decolourisation of the dyes, reaching a peak of 70% dye degradation at pH 2 after 2 h with a catalyst dose of 0.9 g/L. The most pronounced effect was observed against Bacillus subtilis (22 mm), whereas the least impact was noted for Pseudomonas aeruginosa (14 mm). Furthermore, the developed nanoparticles underwent antioxidant activity analysis, revealing that 1 gm of nanoparticles possesses antioxidant activity equivalent to 4.22 mg of ascorbic acid.

Optimization of methyl orange decolorization by bismuth(0)-doped hydroxyapatite/reduced graphene oxide composite using RSM-CCD

In the current study, the catalyst for the decolorization of methyl orange (MO) was developed HAp-rGO by the aqueous precipitation approach. Then, bismuth(0) nanoparticles (Bi NPs), which expect to show high activity, were reduced on the surface of the support material (HAp-rGO). The obtained catalyst was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The parameters that remarkably affect the decolorization process (such as time, initial dye concentration, NaBH4 amount, and catalyst amount) have been examined by response surface methodology (RSM), an optimization method that has acquired increasing significance in recent years. In the decolorization of MO, the optimum conditions were identified as 2.91 min, Co: 18.85 mg/L, NaBH4 amount: 18.35 mM, and Bi/HAp-rGO dosage: 2.12 mg/mL with MO decolorization efficiency of 99.60%. The decolorization process of MO with Bi/HAp-rGO was examined in detail kinetically and thermodynamically. Additionally, the possible decolorization mechanism was clarified. The present work provides a new insight into the use of the optimization process for both the effective usage of Bi/HAp-rGO and the catalytic reduction of dyes.

Photocatalytic degradation of Acid Red 18 by synthesized AgCoFe2O4@Ch/AC: Recyclable, environmentally friendly, chemically stable, and cost-effective magnetic nano hybrid catalyst

Chitosan (Ch) is a linear biodegradable natural carbohydrate polymer and the most appealing biopolymer, such as low-cost biodegradability, biocompatibility, hydrophilicity, and non-toxicity. In this case, Ch was utilized to synthesize AgCoFe2O4@Ch/Activated Carbon (AC) by the modified microwave-assisted co-precipitation method. The physical and chemical structure of magnetic nanocomposites was analyzed and characterized by Field Emission Scanning Electron Microscope (FESEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Diffuse Reflection Spectroscopy (DRS), Value stream mapping (VSM), Fourier transform spectroscopy (FTIR) and BET. The effects of various parameters on the removal of dye (Acid Red18), including catalyst dose, dye concentration, pH, and time were studied. Results showed that the highest removal efficiencies were 96.68 % and 84 % for the synthetic sample and actual wastewater, respectively, in optimal conditions (pH: 3, the initial dye concentration: 10 mgL−1, the catalyst dose: 0.14 gL−1, time: 50 min). Mineralization, according to the COD analysis, was 89.56 %. Photocatalytic degradation kinetics of Acid Red 18 followed pseudo-first order and Langmuir-Hinshelwood with constants of kc = 0.12 mg L−1 min−1 and KL-H = 0.115 Lmg−1. Synthesized photocatalytic AgCoFe2O4@Ch/AC showed high stability and after five recycling cycles was able to remove the pollutant with an efficiency of 85.6 %. So, the synthesized heterogenous magnetic nanocatalyst AgCoFe2O4@Ch/AC was easily recycled from aqueous solutions and it can be used in the removal of dyes from industries with high efficiency.

Synthesis of CoFe2O4/TiO2/PANI Nanocomposite Photocatalyst, and Examination of Its Decolorization Efficiency on Rhodamine B

AbstractThis study aims to reduce the band gap by doping wide band‐gap TiO2 with CoFe2O4 and PANI to improve the photocatalytic efficiency and examine the decolorization kinetic of Rhodamine B (RhB). The characteristics of the nanocomposites were thoroughly assessed through the utilization of SEM‐EDS, TEM, XRD, FTIR, VSM, UV‐Vis, PL, and XPS analyses. The SEM and TEM analyses revealed that CoFe2O4/TiO2/PANI has a homogeneously porous structure. XRD analysis results were found to show good agreement with the standard diffraction data cards. The band structures obtained by FTIR analyses were compatible with literature studies. The band gap energies determined by UV‐Vis analyses were determined as 2.86 eV for CoFe2O4/TiO2/PANI. The decrease of CoFe2O4/TiO2/PANI recombination rate was proven with PL results. The different initial dye concentrations, temperature, and light intensity parameters were used to determine the decolorization kinetics of RhB over CoFe2O4/TiO2/PANI. The photodegradation rates of RhB in reactions catalyzed by PANI, CoFe2O4, commercial‐TiO2, CoFe2O4/TiO2, and CoFe2O4/TiO2/PANI were determined as 7.6 %, 20.7 %, 26.6 %, 32.4 %, and 48.8 %, respectively. According to data obtained from the decolorization of RhB on CoFe2O4/TiO2/PANI nanocomposite, the appropriate kinetic model was determined Network kinetic. The adsorption equilibrium constant (KB) and activation energy (Ea) were calculated as 0.007 and 7.9 kJ/mol, respectively.

Feasibility and sludge analysis of electrocoagulation process for Direct Violet-35 dye remediation

The present study investigates Direct Violet-35 (DV-35) remediation using electrocoagulation process. DV-35 which is an industrial azo dye, after release significantly affects the visual appearance of water bodies and hinders the process of photosynthesis affecting plant growth. Perturbing the food chain, it promotes toxicity, mutagenicity, and carcinogenicity. Therefore, dye remediation is essential before discharge into water streams. To determine the effectiveness of the electrocoagulation process for DV-35 dye remediation, and understand the influence of parameters like current density, inter-electrode spacing, concentration of electrolyte, pH, agitation speed, and initial dye concentration, a detailed study was carried out. Maximum removal efficiency (>98 %) was achieved in 16 min at 263.15 A/m2 current density and pH 7.2 for DV-35 concentration of 50 to 500 mg/L. Further, optimized parameters were applied to real textile effluent achieving 99.8 % efficiency. EC mechanism was corroborated by Sips isotherm matching adequately with experimental results. The findings also demonstrated a heterogeneous surface of the produced EC flocs. Pseudo-second-order was obtained with a low operating cost of 0.0018 US $/m3. The DV-35 removal and functional groups were confirmed by UV/VIS and Fourier transforms infrared spectroscopy analysis. The sludge was examined by X-ray Diffraction and Scanning Electron Microscope revealing Crystalline aluminum oxides i.e. bayerite (Al(OH)3) and diaspore (AlO(OH)). The conclusion of the results revealed EC to be an effective and economical technique for DV-35 remediation from textile wastewater.

Preparation of styrene-based imprinted polymer for the adsorption of hazardous bromocresol green dye: Equilibrium, kinetics and thermodynamics study

In this study, styrene was used as a functional monomer for the production of molecularly imprinted polymer (MIP) via free radical polymerization method, using bromocresol green dye (BCG) as template. A non-imprinted polymer (NIP), that excluded the template, was also synthesized. Both polymers were applied for the removal of BCG from aqueous medium. The synthesized polymers were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray powder diffraction spectroscopic techniques. The effect of operating variables, such as pH, contact time, initial dye concentration and process temperature, on the efficiencies of the polymers in removing the dye were evaluated. Equilibrium time of BCG adsorption onto the MIP was reached within 40 min, with adsorption capacity of 49.68 mg g-1 . The adsorption process followed the pseudo-second-order kinetic and Freundlich isotherm models, while chemisorption mechanism was predicted. The adsorption process was spontaneous and exothermic in nature, with DH values of -140.03 and -25.01 kJ/mol-1 recorded for BCG removal by MIP and NIP, respectively. The styrene-based MIP showed good mechanical stability, and retained up to about 99% of its adsorption capacity after six sequential cycles of regeneration. Comparatively, the MIP (99.81mg g-1 ) performed considerably better than its NIP (59.00 mg g-1 ) analogue in the removal of BCG from aqueous medium, thus affirming the potentials of the molecular imprinting technique in the production of efficient adsorbents for adsorption of toxic dyes from industrial effluents.

Optimization and modelling of magnesium oxide (MgO) photocatalytic degradation of binary dyes using response surface methodology

Textile industry dye effluent contains a mixture of different kinds of dyes. Many times, photocatalysis is targeted as a solution for the treatment of dye effluent from the textile industry. Many researches have been published related to the photocatalysis of single textile dyes but in the real-world scenario, effluent is a mixture of dyes. Magnesium oxide (MgO) is used as a photocatalyst to treat a mixture (binary solution) of Methylene blue (MB) and Methylene violet (MV) along with individual MB and MV dyes in this article. MgO shows remarkable photocatalytic activity at about 93 and 88% for MB and MV dye in binary solution within 135 min. Furthermore, to study the influence of process parameters, experiments are designed with the help of the central composite design (CCD), and Response surface methodology (RSM) is used to study the interactions between parameters. For this study, five parameters are selected i.e., Photocatalyst dosage, initial concentration of both dyes, time of exposure to the light source, and pH of the binary solution. The photocatalytic process is also optimized and finally optimization of process parameters is validated with an experiment. The result of the validation experiment is very close to the predicted photocatalytic activity.

Tuning physicomechanical properties of PEG-interpenetrated anionically modified semi-IPN cryogels functionalized with carboxylate groups

Anionically modified interpenetrated polymer network (semi-IPN) cryogels containing linear polyethylene glycol chains (PEG) were prepared via in situ synthesis and directed assembly of the negatively charged copolymer poly(acrylamide-co-sodium acrylate) (PAN) network template. The influence of reaction conditions; the concentration of linear PEG chains, and polymerization temperature on the elasticity and swelling of these IPNs was analyzed in detail. The interpenetrating structure of PEG chains and PAN host network have been confirmed by FTIR, TGA and XRD analysis. The equilibrium water content, oscillatory swelling/deswelling kinetics, and water transport mechanism were analyzed as a function of PEG content. The results showed that semi-IPN gels exhibited different swelling behavior as the reaction conditions varied. Addition of 13.9% (w/v) PEG resulted in a 25-fold increase in the swelling ratio of semi-IPN hydrogels. By performing compression tests on semi-IPN gels to determine the change of compression properties, the effective cross-linking density of semi-IPN PAN/PEG was expressed as a second-order polynomial depending on the amount of PEG. The swollen modulus of semi-IPN cryogels was much higher than that of semi-IPN hydrogels for all PEG concentrations. Semi-IPNs showed reversible on-off switching with remarkable sensitivity to external pH stimulus. Structural parameters, degree of swelling, volume fraction of cross-linked polymer in the swollen state, and diffusion coefficients due to pH-induced swelling of semi-IPN gels were determined. The presence of linear PEG chains in the structure promoted swelling by both increasing the swelling rate and significantly reducing the time required to reach the equilibrium-state. The swelling process was Fickian diffusion, and the diffusion coefficients for swelling of PEG-interpenetrated semi-IPNs increased with PEG content. The effectiveness of removing methylene blue (MB) dye from aqueous solutions by semi-IPNs was evaluated. Batch adsorption experiments were performed as a function of the gelation temperature, amount of PEG, contact time, and initial dye concentration. The adsorption isotherm and kinetics were described well by Langmuir isotherm model and pseudo-second-order model, respectively. Adsorption of MB was a multi-step process involving surface adsorption followed by intra-particle diffusion. Semi-IPN PAN/PEG cryogels prepared under cryocondition with high adsorption capacities and fast adsorption rates have been developed as new adsorbents effective in removing dyes and other toxic substances with higher mechanical strength in water and wastewater treatment.