Comprehensive batch and continuous methyl orange removal studies using surfactant modified chitosan-clinoptilolite composite

Innovative Sol-gel functionalized polyurethane foam for sustainable water purification and analytical advances

Nanomaterial combined polymeric membranes such as polyurethane foams (PUFs) have garnered enormous attention in the field of water purification due to their ease of management and surface modification, cost-effectiveness, and mechanical, chemical, and thermal properties. Thus, this study reports the use of novel Sol-gel impregnated polyurethane foams (Sol-gel/PUFs) as new dispersive solid phase microextractors (d- µ SPME) for the efficient separation and subsequent spectrophotometric detection of Eosin Y (EY) textile dye in an aqueous solution with a pH of 3-3.8. The Sol gel, PUFs, and Sol gel-impregnated PUFs were characterized using scanning electron microscopy (SEM), goniometry measurements, dynamic light scattering (DLS), energy dispersive spectroscopy (EDS), UV-Visible, and FTIR spectra. Batch experiment results displayed a remarkable removal percentage (96% ± 5.4%) of the EY from the aqueous solution, with the total sorption time not exceeding 60 min. These data indicate rate-limited sorption via diffusion and/or surface complex ion associate formations after the rapid initial sorption steps. A pseudo-second order kinetic model thoroughly explained the sorption kinetics, providing a sorption capacity (qe) of 37.64 mg g-1, a half-life time (t1/2) of 0.8 ± 0.01 min, and intrinsic penetration control dye retention. The thermodynamic results revealed a negative value for ΔG⁰ (-78.07 kJ mol-1 at 293 K), clearly signifying that the dye uptake was spontaneous, as well as a negative value for ΔH⁰ (-69.58 kJ mol-1) and a positive value for ΔS⁰ (147.65 J mol-1 K-1), making clear the exothermic nature of EY adsorption onto the sorbent, with a growth in randomness at the molecular level. A ternary retention mechanism is proposed, involving the "weak base anion exchanger" of {(-CH2-OH+ -CH2-) (Dye anion)-}Sol-gel/PUF and/or {(-NH2 + -COO-) (Dye anion)-}Sol-gel/PUF via solvent extraction and "surface adsorption" of the dye anion on/in the Sol-gel/PUFs membranes in addition to H-bonding, including surface complexation and electrostatic π-π interaction, between the dye and the silicon/zirconium oxide (Si-O-Zr) and siloxane (Si-O-Si) groups on the sorbent. Complete extraction and recovery (93.65 ± 0.2, -102.28 ± 2.01) of EY dye with NaOH (0.5 M) as a proper eluting agent was achieved using a sorbent-packed mini column. In addition, the established extractor displayed excellent reusability and does not require organic solvents for EY enrichment in water samples, making it a talented nominee as a novel sorbent for EY sorption from wastewater. This study is of great consequence for expanding the applicatio1n of Sol-gel/PUFs in developing innovative spectrophotometric sensing strategies for dye determination. In view of this, it would also be remarkable to perform future studies to explore the analytical implications of this extractor regarding safety and environmental and public health issues associated to the pollutant.

Magnetic nanocomposite of maize offal biomass for effective sequestration of Congo red and methyl orange dyes from contaminated water: modeling, kinetics and reusability

The current study aims to use a facile and novel method to remove Congo red (CR) and Methyl Orange (MO) dyes from contaminated water with Maize offal biomass (MOB) and its nanocomposite with magnetic nanoparticles (MOB/MNPs). The MOB and MOB/MNPs were characterized with Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), BET, XRD and point of zero charge (pHPZC). The influence of initial CR and MO levels (20-320 mg/L), adsorbent dosage (1-3 g/L), pH (3-9), co-exiting ions, temperature (25-45 °C) and time (15-180 min) was estimated. The findings demonstrated that MOB/MNPs exhibited excellent adsorption of 114.75 and 29.0 mg/g for CR and MO dyes, respectively while MOB exhibited 81.35 and 23.02 mg/g adsorption for CR and MO dyes, respectively at optimum pH-5, and dose 2 g/L. Initially, there was rapid dye removal which slowed down until equilibrium was reached. The interfering/competing ions in contaminated water and elevated temperature favored the dyes sequestration. The MOB/MNPs exhibited tremendous reusability and stability. The dyes adsorption was spontaneous, and exothermic with enhanced randomness. The adsorption effects were well explained with Freundlich model, pseudo second order and Elovich models. It is concluded that MOB/MNPs showed excellent, eco-friendly, and cost-effective potential to decontaminate the water.

Sol-Gel Functionalized Polyurethane Foam-Packed Mini-Column as an Efficient Solid Extractor for the Rapid and Ultra-Trace Detection of Textile Dyes in Water

Textile dyes widely used in industrial products are known as a major threat to human health and water ecological security. On the other hand, sol gel represents a principal driver of the adoption of dispersive solid-phase microextractors (d-µ SPME) for pollutants residues in water. Thus, the current study reports a new and highly rapid and highly efficient hybrid sol-gel-based sponge polyurethane foam as a dispersive solid-phase microextractor (d-µ-SPME) platform packed mini-column for complete preconcentration and subsequent spectrophotometric detection of eosin Y textile dye in wastewater. The unique porous structure of the prepared sol-gel immobilized polyurethane foams (sol-gel/PUF) has suggested its use for the complete removal of eosin Y dye (EY) from water. In the mini-column, the number (N) of plates, the height equivalent to the theoretical plates (HETP), the critical capacity (CC), and the breakthrough capacities (BC) of the hybrid sol-gel-treated polyurethane foams towards EY dye were determined via the breakthrough capacity curve at various flow rates. Under the optimum condition using the matrix match strategy, the linear range of 0.01-5 µg L-1, LODs and LOQs in the range of 0.006 µg L-1, and 0.01 µg L-1 for wastewater were achieved. The intra-day and inter-day precisions were evaluated at two different concentration levels (0.05 and 5 μg L-1 of dye) on the same day and five distinct days, respectively. The analytical utility of the absorbents packed in pulses and mini-columns to extract and recover EY dye was attained by 98.94%. The column could efficiently remove different dyes from real industrial effluents, and hence the sol-gel/PUF is a good competitor for commercial applications. The findings of this research work have strong potential in the future to be used in selecting the most suitable lightweight growing medium for a green roof based on stakeholder requirements. Therefore, this study has provided a convenient pathway for the preparation of compressible and reusable sponge materials from renewable biomass for efficient removal of EY from the water environment.

Modification of natural zeolite clinoptilolite and ITS application in the adsorption of herbicides

The clinoptilolite natural zeolites (NZs) posses low herbicide adsorption capacity demanding acid-, alkali-, or salt chemical modifications that enhance its adsorption. However, this may affect the material structure and charge distribution. Alternatively, zeolites may be synthesized at a high cost and time-consuming process. Consequently, new methods, such as the hydrothermal method, for NZ modification needs to be studied. In this sense, a novel surface-modified zeolite (SMZ), using hexadecyltrimethylammonium bromide (CTAB), in acid media was produced by the hydrothermal method and applied for the adsorption of Atrazine (ATZ), Diuron (DIU) and 2,4-D. Commercial NZ and SMZ were characterized by SEM, XRD, TGA, FT-IR, AA spectroscopy, pHPZC, Zeta potential and N2-physisorption. The SMZ chosen for the adsorption experiments was the one with the highest modification yield and adsorption capacity obtained from a complete design of experiments (CTAB=0.74 ; D=12 Mesh; HCl=0.1 M; t=6 h and T=205 ºC). The adsorption experiments revealed that the SMZ adsorption capacity for the herbicide 2,4-D (qmax=9.02 mg/g) was greater than that obtained for ATZ (qmax=2.11 mg/g) and DIU (qmax=1.85 mg/g), which was explained by the presence of the hydroxyl group and by geometric characteristics of the 2,4-D. Adsorption models' fitting showed that the adsorption of 2,4-D onto SMZ were best described by pseudo-second order kinetic (k2=0.005-0.006 g/mg.min; qe,exp=7.122-8.614 mg/g) and Langmuir isothermal model (KL=0.283-0.499 L/mg; qm=7.167-7.995 mg/g). These results indicate that the hydrothermal method is a viable alternative to enable the use of NZs for the adsorption of emerging contaminants from wastewater.

In-situ biofabrication of bacterial nanocellulose (BNC)/graphene oxide (GO) nano-biocomposite and study of its cationic dyes adsorption properties

In the present study, bacterial nanocellulose/graphene oxide nano-biocomposites (BNC-GO-NBCs) were fabricated by Komagataeibacter saccharivorans NUWB1 using an in-situ method involving three time-dependent approaches. Physicochemical studies showed that the chosen dried BNC-GO-NBC possessed a three-dimensional interconnected porous structure of BNC with GO layers embedded within the BNC fibrils. BNC-GO-NBC had a crystallinity index of 74.21 %, higher thermostability up to 380 °C and could withstand a tensile load of 84.72 MPa. N2 adsorption-desorption isotherm of the BNC-GO-NBC was found to be of type IV, suggesting a mesoporous type structure with a total pore volume and surface area of 6.232e-04 cc g-1 and 10.498 m2. BNC-GO-NBC exhibited remarkable adsorption capacity for two cationic dyes, Rhodamine B (RhB) and Acridine Orange (AO), and the adsorption data conformed well to the Langmuir isotherm (R2 = 0.99) and pseudo-second-order model. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. Additionally, the BNC-GO-NBC displayed the potential for regeneration, with the ability to be recycled up to five times. Further, the antibacterial activity, cell cytotoxicity and oxidative stress assays of the BNC-GO-NBC revealed its non-cytotoxic nature. The findings of the present investigation evidently suggest the potentiality of BNC-GO-NBC in the application of dye adsorption and other environmental applications.

Surfactant supported chitosan for efficient removal of Cr(VI) and anionic food stuff dyes from aquatic solutions

In order to develop a novel and cost-effective adsorbent with outstanding adsorption capacity and excellent recyclability for anionic pollutants, the chitosan-modified cetyltrimethylammonium bromide sorbent (CS@CTAB) was fabricated. Fourier-transform infrared spectroscopy, N2 adsorption-desorption isotherm, elemental analysis, Thermogravimetric analysis, X-ray diffraction, and Scanning electron microscopy have been applied to evaluate both raw and surfactant modified chitosan (CS@CTAB). Azorubine, Sunset Yellow, and hexavalent chromium were used to study the adsorption behavior of CS@CTAB under various parameters such as adsorbent dose, initial dye and metal ion concentration, contact time, and temperature. Adsorption equilibrium, kinetics models and thermodynamic parameters were investigated. The adsorption isotherm fitted well with the Langmuir isotherm model, with a maximum adsorption capacity of 492.6 mg/g, 492.6 mg/g, and 490.196 mg/g for Azorubine, Sunset Yellow, and Hexavalent Chromium, respectively. The kinetic studies showed that the pseudo-second-order model provided a better correlation between experimental data. Furthermore, the calculated thermodynamic parameters confirmed that the adsorption of Cr(VI), E110, and E122 by CS@CTAB material is a spontaneous and exothermic process. The fabricated CS@CTAB adsorbent was employed for the efficient elimination of Azorubine, Sunset Yellow, and hexavalent chromium from real water samples, synthetic mixtures, and colored soft drinks, with a percentage of recovery of ~ 96%. The plausible adsorption mechanisms of Azorubine, Sunset Yellow, and hexavalent chromium on the surface of CS@CTAB are elucidated. The adsorption anticipated to be due to electrostatic interaction and hydrogen bond formation for hexavalent chromium; while the adsorption of Azorubine and Sunset Yellow, was assumed to be due to electrostatic interaction, hydrogen bonding, and n-π interaction. Finally, the study demonstrates the efficiency of CS@CTAB for the removal of anionic species from several samples, including natural water and colored beverages.

Column adsorption of biological oxygen demand, chemical oxygen demand and total organic carbon from wastewater by magnetite nanoparticles-zeolite A composite

Herein, magnetite nanoparticles (NPs), zeolite A and magnetite-zeolite A (MAGZA) composite was developed by green methods. The produced nanomaterials were characterized and the effect of process parameters such as flow rate, adsorbent bed height and adsorbate inlet concentration was evaluated for the removal of biological oxygen demand (BOD), chemical oxygen demand (COD) and total organic carbon (TOC) in a column. The characterization results demonstrated the successful synthesis of magnetite NPs, zeolite A and MAGZA composite. The performance of the MAGZA composite in the fixed-bed column was superior to zeolite A and magnetite NPs. The parametric influence indicates that an increase in bed height and a decrease in the flow rate and inlet adsorbate concentration improved the performance of the adsorption column. The adsorption column demonstrated maximum performance at a flow rate (4 mL/min), bed height (5 cm) and inlet adsorbate concentration (10 mg/L). Under these conditions, the highest percent removal of BOD, COD and TOC were 99.96, 99.88 and 99.87%. Thomas and Yoon-Nelson's model suitably fitted the breakthrough curves. After five reusability cycles, the MAGZA composite demonstrated removal percent of BOD (76.5%), COD (55.5%) and TOC (64.2%). The produced MAGZA composite effectively removed BOD, COD and TOC from textile wastewater in a continuous operating mode.

Simultaneous CO2 reduction and NADH regeneration using formate and glycerol dehydrogenase enzymes co-immobilized on modified natural zeolite

In this work, the co-immobilization of formate dehydrogenase (FDH) and glycerol dehydrogenase (GlyDH) enzymes is proposed to reduce CO₂ into formic acid, an important chemical intermediate. The reduction of carbon dioxide is carried out by FDH to obtain formic acid, simultaneously, the GlyDH regenerated the nicotinamide cofactor in the reduced form (NADH) by the oxidation of glycerol into dihydroxyacetone. Natural zeolite was selected as immobilization support given its good properties and low cost. The natural zeolite was modified with subsequent acid-alkaline attacks to obtain a mesostructurization of the clinoptilolite. The two enzymes were co-immobilized on clinoptilolite, previously hetero-functionalized with amino and glyoxyl groups. The distribution of the enzymes was confirmed by fluorescence microscopy analysis. Furthermore, a great increase in the retained activity for the formate dehydrogenase enzyme was noted, passing from 18% to 89%, when the mesostructured clinoptilolite was used as support. The immobilization yield of formate dehydrogenase and glycerol dehydrogenase is around 100% with all the supports studied. The promising results suggest a possible development of this procedure in enzyme immobilization and biocatalysis. The biocatalysts were characterized to find the optimal pH and temperature. Furthermore, a thermal stability test at 50 °C was carried out on both enzymes, in free and immobilized forms. Finally, it was shown that the biocatalyst is effective in reducing CO₂, both by using the cofactor in the reduced form (NADH) or the oxidized form (NAD⁺), obtaining NADH through the regeneration with glycerol in this latter case.

Mass-Transfer Simulation of Salicylic Acid on Weakly Polar Hyper-cross-linked Resin XDA-200 with Coadsorption of Sodium Ion

The mass-transfer process of salicylic acid on hyper-cross-linked resin XDA-200 was experimentally and theoretically studied. Undissociated salicylic acid was found to be the favorable form for salicylic acid adsorption on the resin. A pH-dependent adsorption isotherm model established in this paper could well fit the adsorption isotherm data at different pH values. Surface diffusion is the main mass-transfer mode for salicylic acid in resin particles. The salicylate anions and Na+ coadsorbed on the resin. The modified surface diffusion model considering the coadsorption was proposed. The model could satisfactorily fit the concentration decay curves of salicylic acid at different pH values and feed concentrations. NaOH aqueous solution at pH 12 could elute salicylic acid in the fixed bed efficiently. A pH-dependent dynamic adsorption and elution process model considering axial diffusion, external mass transfer, surface diffusion, pH-dependent adsorption equilibrium, as well as coadsorption of salicylate anions and Na+ was established. The model could well predict the breakthrough and elution curves at different feed concentrations. The research carried out in this paper has reference significance for optimizing the separation process of salicylic acid and its analogues.

Recent advances of biosurfactant for waste and pollution bioremediation: Substitutions of petroleum-based surfactants

Biosurfactant is one of the emerging compounds in the industrial sector that behaves similarly with their synthetic counterparts, as they can reduce surface and interfacial tension between two fluids. Their unique properties also enable biosurfactant molecules to be able to clump together to form micelles that can capture targeted molecules within a solution. Biosurfactants are compared with synthetic surfactants on various applications for which the results shows that biosurfactants are fully capable of replacing synthetic surfactants in applications including enhanced oil recovery and wastewater treatment applications. Biosurfactants are able to be used in different applications as well since they are less toxic than synthetic surfactants. These applications include bioremediation on oil spills in the marine environment and bioremediation for contaminated soil and water, as well as a different approach on the pharmaceutical applications. The future of biosurfactants in the pharmaceutical industry and petroleum industry as well as challenges faced for implementing biosurfactants into large-scale applications are also discussed at the end of this review.

Bimetallic Fe/Al-MOF for the adsorptive removal of multiple dyes: optimization and modeling of batch and hybrid adsorbent-river sand column study and its application in textile industry wastewater

Bimetallic metal organic framework (MOF) has garnered interest over the years with its applications in industrial wastewater treatment. In this work, Fe-Al-1,4-benzene-dicarboxylic acid (FeAl(BDC)) MOF was synthesized, and adsorptive removal of Rhodamine B dye in batch and unique hybrid FeAl (BDC)-river sand fixed-bed column was studied. The experimental data from the batch studies corroborated well with the pseudo-second-order (PSO) (R²: 0.97) and Freundlich adsorption isotherm models (R²: 0.98) and achieved a maximum adsorption capacity of 48.59 mg/g in 90 min. Furthermore, a fixed-bed column study was conducted to assess the effect of varying flow rate (2, 5, 8 mL/min), bed height (5, 9, 13 cm), and feed concentration (10, 20, 30 mg/L) on the adsorption performance of FeAl(BDC) in continuous mode of operation. A uniform mixture of river sand and FeAl(BDC) by weight ratio (9:1) was packed into the column. The sand-FeAl(BDC) fixed-bed column could achieve the maximum adsorption capacity (q_exp) of 113.05 mg/g at a 5 mL/min flow rate, feed concentration of 20 mg/L, and a bed height of 13 cm. The experimental data of the column study were successfully fitted well with BDST, Thomas (q_cal: 114.94 mg/g), Yoon-Nelson, and dose-response models (q_cal: 113.41 mg/g) and R²: 0.97-0.99. The fitting parameter values from the BDST model raise the scope of viable upscaling of the fixed-bed column. In all, it is proposed that these river sand-FeAl(BDC)-based filters can be widely used in areas facing critical contamination and in poor communities with a high demand for water.

The surfactant-ionic liquid bi-functionalization of chitosan beads for their adsorption performance improvement toward Tartrazine

In this study, the ionic liquid (Aliquat-336) and anionic surfactant (cetyltrimethylammonium bromide, CTAB) bi-functionalized chitosan beads were prepared and characterised using different techniques, including FTIR, XRD, SEM, EDS and BET surface area analysis. The characteristic analysis confirmed the successful conjugation of chitosan beads with both surfactant and ionic liquid. The novel fabricated beads (CS-CTAB-AL) were efficiently employed, as a high-performance adsorbent, for the removal of Tartrazine (TZ), an anionic food dye, from polluted water. The optimum adsorption of TZ onto the CS-CTAB-AL was found at 2 g L^-1 of adsorbent in the wide pH range of 4-11, whereas just 45 min was required to reach more than 90% adsorption efficiency in the studied conditions. Also, the adsorption and kinetic studies showed that the experimental data well fitted the pseudo-first-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of prepared beads was found to be 45.95 mg g^-1 at 45 °C. The adsorption properties of enabling CS-CTAB-AL conjugation introduced a new type of adsorbents, exploited the combination of ionic liquid and surfactant capabilities for wastewater treatment.

Efficient adsorption of methyl orange and methyl blue dyes by a novel triptycene-based hyper-crosslinked porous polymer

It is still a great challenge to develop new materials for the highly efficient entrapment of organic dyes from aqueous solution. Herein, a novel triptycene-based hyper-crosslinked porous polymer (TPP-PP) was designed and synthesized by a simple Friedel-Crafts reaction. The obtained polymer TPP-PP has a high surface area, abundant pore structure and stable thermal performance. Due to the above characteristics, TPP-PP has good adsorption performance for anionic methyl orange solution (MO) and cationic methyl blue solution (MB). Under the optimal experiment conditions, the TPP-PP showed an excellent adsorption capacity for MO (220.82 mg g-1) and MB (159.80 mg g-1), respectively. The adsorption kinetics fitted the pseudo-second-order model. The adsorption of MO by TPP-PP reaches equilibrium within 180 minutes, and the adsorption of MB reaches equilibrium within 150 minutes. The adsorption behavior was not only spontaneous but also endothermic in reality. At the same time, TPP-PP also has good reusability. After 5 cycles of experiments, the removal rate of MO and MB by TPP-PP can still reach more than 80%. Thus, the Friedel-Crafts reaction crosslinked method might be a promising approach for the synthesis of novel material for the highly efficient extraction of dye wastewater.

A chitosan fiber as green material for removing Cr(VI) ions and Cu(II) ions pollutants

The application shell uses cellulose as a green and recyclable fiber material, which has great value in the field of water treatment environment. Varying factors, including pH value, dosage of CS, reaction time and original Cr(VI) ions and Cu(II) ions were studied to investigate the Cr(VI) and Cu(II) ions removal efficiency. The obtained shell trichlorocellulose has better permeability to copper ions, which is mainly due to the different oxide states of copper ions and chromium ions in a pH environment, which lead to different combinations. The price of shell cellulose neutralization is relatively low. Metal ions have better absorption properties. The kinetic and thermodynamic characteristics of the adsorption process of copper ions by chitosan yarns were discussed. The adsorption process of copper ions conformed to the quasi-second-order kinetic equation. It can be fitted by Langmuir isotherm. The adsorption of copper ions by the yarn is a spontaneous thermal reaction with both physical adsorption and chemical adsorption. Compared with chromium ions, chitosan fibers have better adsorption of copper ions, which is mainly because the amino groups in chitosan fibers can have good chelation with copper ions. SEM, FTIR, XRD were used to characterize the adsorption of copper ions by chitosan fibers, and the mechanism of the adsorption of metal ions by chitosan fibers was explored.