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Adsorption removal of Brilliant green and Safranin‐O contaminants from water using a hydrogel based on carboxymethyl cellulose and sodium alginate crosslinked by epichlorohydrin
Abstract
The present study explained complete investigation for the adsorption properties of chemically cross linked hydrogel based on sodium alginate (NaALG) and carboxymethyl cellulose (CMC). The structural characteristics of the investigated hydrogel were described using information from FT‐IR spectra, XRD patterns, and FESEM pictures. The synthesized NaALG/ECH/CMC hydrogel was synthesized under optimized condition with respect to swelling percentage. Various reaction parameters were varied in order to get the maximum percentage swelling. The synthesized hydrogel was taken as adsorbents in the decolorization of Brilliant green (BG) and Safranin‐O (SO) dyes from water. According to the kinetic investigations, the decolorization equilibrium of SO by NaALG/ECH/CMC was discovered in 4 hour (98.98 %), while the removal of BG by NaALG/ECH/CMC took 6 hour (97.7 %). Chemical processes were used to describe the decolorization mechanisms, which significantly supported Pseudo first order model. NaALG/ECH/CMC hydrogel absorption was indicated to take place in monolayer adsorption form (Langmuir Isotherm). The highest adsorption capacity for BG was discovered to be 864.8 mg/g and for SO was 193.1 mg/g by synthesized hydrogel where 'mg' refers to commercial colorant, not pure dye. Therefore, the synthesized hydrogel can be considered as smart device for the adsorption of dye in water purification tasks.
... Generally, the higher the ionic radius is the lower the electrostatic attraction, which resulted in adsorption capacity reduction. For pollutants like lithium, boron, and molybdenum with small crystal radius values (0.9 Å, 0.98 Å, and 2.01 Å), respectively, it was assumed that the ions migrated into the pores of GO-CNC@DP (intra-particle diffusion) after being adsorbed on the surface (inter-particle diffusion) (Vaid et al., 2022). In other words, the adsorption process occurs through three steps. ...
... XRD patterns of CMC and CMC-based nanocomposite gels are shown in Fig. 1(II). CMC gel and S5 showed the crystalline mode of CMC at 2θ of 29.3 • [35], and this peak shifted to 29.7 • for S1 and S4 due to the formation of AgCl. There were diffraction peaks at 2θ of 33.2 • and 47.1 • , belonging to (200) and (220) planes of cubic NaCl crystal (JCPDS cards NO. 05-0628), and the intensity of these peaks for S1, S4 and S5 decreased. ...
Antibacterial sodium carboxymethyl cellulose (CMC) gels were prepared via immobilizing ZnO and/or Ag/AgCl in situ to inhibit the aggregation of nano-photocatalyst. Epichlorohydrin was used as a crosslinking agent to prepare CMC gel, simultaneously introducing chlorine-containing branch chains as Cl reservoir to deposit AgCl. The composite gels presented pH responsive swelling properties, with the minimum swelling ratio at pH 8 and pH 4 for CMC gels containing Ag/AgCl and ZnO, respectively. Zn2+ release from the nanocomposite gels was much greater in acidic than in neutral. Photocatalytic degradation constants of methyl orange by the composite gels under sunlight were greater than UV irradiation. Ag/AgCl loaded gel showed a degradation rate of 71.3 % under sunlight for 1 h, with a rate constant approximately 10.2 times higher than ZnO loaded gel. Extract liquids with the gel content below 0.33 mg/mL were noncytotoxicity. The nanocomposite gels presented good bactericidal rate against E. coli and S. aureus under sunlight for 6 h, comparatively to those in dark for 24 h. Bacteriostatic activity of Ag/AgCl loaded gel under sunlight for 6 h was much greater than that in dark for 24 h. The biocompatible nanocomposite gels with sunlight-catalyzed antibacterial activity would broaden the application of CMC gels.
Sodium alginate is a natural macromolecule widely used because of its abundance, low cost of acquisition, and rich hydroxyl and carboxyl groups in the matrix. The physical modification of sodium alginate can be made by blending it with polymer materials. The so-yielded alginate complex is commonly unstable in an aqueous environment due to alginate backbones' high hydrophilicity. The chemical modification can remove its hydrophilic groups and introduce special functional groups or polymers onto the alginate backbones to provide excess reaction sites for specific reactions and effective complexation sites for accommodating antibiotics, dyes, heavy metal ions, and radioactive elements. Sodium alginate has been used in water treatment engineering under revised modification protocols. This article also reviews the latest modification protocols for sodium alginate and outlines the novel application of the modified materials. The limitations of modified sodium alginate materials are described, and research prospects are put forward.
In this study, composite microbeads were prepared using Festuca arundinacea seeds and sodium alginate biopolymer at different ratios and utilized as sorbents for the sorption of Safranine T from wastewater. The sorbents were characterized by FTIR, SEM, XRD, and BET analysis. According to BET analysis, the specific surface area of the adsorbents was calculated to be 10.99 m2/g and the surface was found to be mesoporous. The optimum conditions for adsorption studies including initial pH (2−12), concentration (10–50 mg/L), contact time (0–150 min), and adsorbent mass (0.05 g/50 mL-0.25 g/50 mL) were determined at 25 °C. The raw data obtained from sorption tests were applied to Freundlich, Langmuir-1, Langmuir-2, Langmuir-3, Langmuir-4, Temkin, Toth, and Koble-Corrigan isotherm models. The best results were obtained from the Langmuir-2 and accordingly the qm values were calculated as 454.54, 833.33, and 625.00 mg/g for FA, FA-SA-20, and FA-SA-30 at 25 °C, respectively. Adsorption kinetic data illustrated that the process followed the PSO model. Reusability and desorption studies were performed for composite microbeads. Additionally, the thermodynamic studies were performed at 25, 35 and 45 °C. Considering all these results, it was seen that the FA-SA-20 composite had the highest adsorption capacity and the best desorption efficiency.
Chitosan- and Carboxymethyl cellulose-based hydrogel materials are synthesized by incorporating Bentonite and characterized with different characterization techniques like FTIR, FESEM, EDX and XRD. The most optimized conditions for getting maximum percentage swelling were 50 °C temperature, 25 ml of solvent, pH (9), 20 h of reaction time and 1:1 ratio of reactants (CMC/Chitosan), and 0.05 (mol/L) of Bentonite. The synthesized hydrogel materials are evaluated for the removal of toxic dyes like Rose Bengal and Malachite Green. Different kinetic models were used to measure the kinetic parameters, and different isotherm models were used to evaluate the type of adsorption take place on hydrogel materials. During Adsorption process, 91.75% of Rose Bengal and 96.09% of Malachite Green have been removed. The pseudo-second-order kinetic model has been found as the best fitted model for adsorption of dyes on the synthesized hydrogel. From adsorption isotherm studies, it was concluded that the Langmuir model was found to be the best fitted model and the adsorption was found to be homogenous and physical adsorption. The activation energy values for Rose Bengal and Malachite Green were found to 2.36 and 1.22 kJ/mol, respectively, at room temperature which further supports the adsorption is homogenous and by physical interaction means. The negative values of change in Gibbs free energy from 303 K temperature to 333 K temperature further confirmed the adsorption process is spontaneous for both the dyes. The synthesized hydrogel material was found to be an excellent adsorbent to remove these toxic dyes from the waste water and can be utilized as a green and sustainable material for waste water remediation.
Graphical abstract
Natural polysaccharides were used as adsorbents for the removal of toxic dyes from effluents. First, nanocomposites of chitosan (CH), graphene oxide (GO), sodium alginate (ALG), and β-cyclodextrin (β-CD) were synthesized. The synthesized nanocomposites were characterized by XRD, FTIR, FE-SEM, and EDS to know their interactions and morphology. The adsorption performance of GO/ALG/CH and GO/ALG/CH/β-CD nanocomposites was studied by adsorbing rose Bengal (anionic dye) under different reaction conditions (e.g., concentration of dye solution, temperature, adsorbent dosage, adsorption time, and pH). Among the two studied adsorbents, a higher adsorption capacity was reached using GO/ALG/CH/β-CD nanocomposite. It was seen that adsorption of dye increased with the agitation period and attained equilibrium at 540 min for GO/ALG/CH/β-CD and at 660 min for GO/ALG/CH nanocomposite. Various kinetic models were analyzed and from all models, pseudo-second-order was the best fit model for adsorption. The adsorption equilibrium data followed the Langmuir isotherm model that indicated that the adsorption process is a monolayer. The adsorption process was exothermic and spontaneous, and the lower temperature was favorable for rose Bengal dye adsorption. The mechanism of adsorption of rose Bengal involves both physical and hydrogen bonding due to polymer and inclusion formation due to β-CD through host–guest interactions.
Controlled release drug delivery systems have traditionally been regarded as useful devices in the treatment of a variety of disorders. The objective of the present study is the optimization and thermal behavior of graphene oxide (GO) incorporated chitosan (CH) and sodium alginate (ALG)-based nanocomposite. Various reaction parameters such as temperature, time, amount of solvent, ratio of backbones, amount of GO and pH were optimized to obtain maximum percentage swelling. Thermal stability of nanocomposite was analyzed by thermal gravimetric analysis (TGA). Advanced characteristics of GO have been exploited, including a two-dimensional plan surface with several functional groups, improved biocompatibility, low cost, water solubility, and a huge specific surface area available for high drug loading, among others. Because of these characteristics, graphene oxide is an excellent material for loading and releasing a wide range of drugs. Paracetamol (PCM) is widely used as an antipyretic and analgesic. It is sparingly soluble in water. Inclusion complexes were prepared to improve the solubility of drug by host guest interactions. Phase solubility study implies the 1:1 complexation between PCM and β-CD. Inclusion complexes prepared by physical, kneading, co-precipitation and microwave method were characterized by ¹H NMR, ROESY, FT-IR, XRD and SEM. The inclusion complexes were directly loaded into the nanocomposite and the release study of drug was investigated in gastric (pH 2) and intestinal fluids (pH 7.4) at 37 °C. Four kinetic models were applied to investigate the possible mechanism of drug release. From kinetic models, it was concluded that Peppas-Sahlin and Korsmeyer-Peppas equation followed drug release mechanism. Complexation with β-CD leads to slower the drug release rate from the ICs loaded nanocomposite.
Graphical abstract
The objective of this study was to develop an eco‐friendly, cost‐effective, and efficient adsorbent using kappa‐carrageenan (KCG) and tamarind kernel powder (TKP) based cross‐linked 3‐D network hydrogel. The equilibrium swelling capacity of 1429% was achieved by optimization studies. The KCG/TKP hydrogel was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, energy dispersive spectroscopy, and thermogravimetric analysis. This hydrogel was employed for the efficient removal of brilliant green (BG) and rose bengal (RB) dye from wastewater. BG and RB were used as a cationic and anionic model dye, respectively. The adsorption capacity of model dyes on KCG/TKP was investigated under different parameters like dye concentration, pH, temperature, and adsorbent amount. With remarkable adsorption capacity, the hydrogel demonstrated a strong dependence on the pH of the medium. The kinetics, adsorption isotherm, thermodynamic studies, and reusability were investigated. The KCG/TKP hydrogel follows pseudo‐second‐order kinetics and the Langmuir isotherm model for the adsorption of both BG and RB model dyes. Spontaneity and exothermic behavior of the adsorption process were revealed by thermodynamic findings. At pH 9, the maximum adsorption capacity of BG was 840.33 mg g⁻¹ while the maximum adsorption capacity of RB was 168.06 mg g⁻¹ at pH 5.
Despite the high capacity of Co3O4 employed in lithium-ion battery anodes, the reduced conductivity and grievous volume change of Co3O4 during long cycling of insertion/extraction of lithium-ions remain a challenge. Herein, an optimized nanocomposite, Co3O4/nitrogen-doped hemisphere-porous graphene composite (Co3O4/N-HPGC), is synthesized by a facile hydrothermal-template approach with polystyrene (PS) microspheres as a template. The characterization results demonstrate that Co3O4 nanoparticles are densely anchored onto graphene layers, nitrogen elements are successfully introduced by carbamide and the nanocomposites maintain the hemispherical porous structure. As an anode material for lithium-ion batteries, the composite material not only maintains a relatively high lithium storage capacity (the first discharge specific capacity can reach 2696 mA h g⁻¹), but also shows significantly improved rate performance (1188 mA h g⁻¹ at 0.1 A g⁻¹, 344 mA h g⁻¹ at 5 A g⁻¹) and enhanced cycling stability (683 mA h g⁻¹ after 500 cycles at 1 A g⁻¹). The enhanced electrochemical properties of Co3O4/N-HPGC nanocomposites can be ascribed to the synergistic effects of Co3O4 nanoparticles, novel hierarchical structure with hemisphere-pores and nitrogen-containing functional groups of the nanomaterials. Therefore, the developed strategy can be extended as a universal and scalable approach for integrating various metal oxides into graphene-based materials for energy storage and conversion applications.
Activated carbon has been used as an adsorbent in this work to remove mercury from aqueous solutions. The aim of the work is to test how best activated carbon can be used as an adsorbent for mercury. Equilibrium isotherms, both, Dubinin-Redushkevich, and Temkin have been test. The batch experiments were conducted at room temperature (30 o C) and at the normal pH (7.0±0.1) of the solution. HYBRID fraction error function analysis shows that the best-fit for the adsorption equilibrium data is represented by (D-R) model rather than Temkin model. Its found that the correction factor (R 2) for (D-R) is 0.9928 while for Temkin model is 0.942, also the HYBRID fractional error was conducted for the both models and (D-R) model give minimum value of (0.0128) while it was (0.129) for Temkin. : الخالصة القاراةر اجراا الى البحث ٌهدف قيدٌر قرر اٌريرٌٌر قريدٌلٌر لفرعلٌر Dubinin-Redushkevich يقيدٌر Temkin عقلٌ ليصف التجررا اجراا ترم يقد. القةشط الكرابير برستخدام القرئً القحلي يقر الزئبق اقتزاز حرااا داجر يرً القتاطعر 303 (يقٌق pH=7 (التصحٌح قعرق ار يجد يقد) R 2 (ٌسريي االي الاٌريً للقيدٌ) 0.9928 الثررةً للقيدٌ الاٌق كرةت بٌةقر) (رريي تسر 0.942 (ررا قعٌر رق تطبٌر رم تر ركلت كر) HYBRID (رريي ٌسر االي ر للقيدٌر رل قٌقتر ار رد ييجر رج للخطر رً االةحااير) 0.0128 رر بٌةقر) (الثرةً للقيدٌ 0.129 .)
The current study focused on the use of gum Arabic grafted polyacrylamide (GA-cl-PAM) hydrogel as a self-template for the in situ synthesize of zinc oxide nanoparticles (ZnO NPs) and the application of synthesized nanocomposite as a potential adsorbent to remove synthetic dyes especially malachite green (MG) from aqueous solution. Different characterization techniques supported in situ synthesis of ZnO NPs onto polymer matrix. The gum Arabic-crosslinked-poly(acrylamide)/zinc oxide nanocomposites (i.e., GA-cl-PAM/ZnO nanocomposite) exhibited much better surface properties as compared to the parental hydrogel matrix. The swelling abilities of the GA-cl-PAM/ZnO nanocomposites with different concentrations of acrylamide were also checked and the nanocomposite with 7.03 × 10–4 mol/L of acrylamide exhibited maximum swelling capacity of 2354%. The nanocomposite adsorbed approximately 99% MG dye with 0.4 g/L adsorbent dose at neutral pH. Adsorption kinetics and isotherm followed pseudo-second-order and Langmuir isotherm models, respectively with the high adsorption capacity of 766.52 mgd/gads at 25 °C. It was observed that the dye molecules were adsorbed onto GA-cl-PAM/ZnO nanocomposite mostly via electrostatic interactions, hydrogen-bonding and pore-diffusion mechanisms. Diffusion of dye molecules within the internal structure of GA-cl-PAM/ZnO nanocomposite followed the combination of both liquid film as well as intraparticle diffusion mechanisms. Furthermore, nanocomposite was applied ten times consecutively to adsorb MG dye from aqueous solution. Therefore, GA-cl-PAM hydrogel have capability to be used for the in situ ZnO NPs synthesis and thus synthesized nanocomposite can be used effectively to treat dyes polluted wastewater.
In the present study, monodispersed silica nanoparticles (SNPs) were synthesized by sol–gel method. To enhance the properties like surface roughness, surface area, and percentage swelling, the SNPs were incorporated into the hydrogel Gelatin and Psyllium to synthesize a nanocomposite material. The percentage of swelling was optimized by varying different reactions parameters like temperature, pH, backbone ratio, monomer concentration, cross-linker concentration, initiator concentration and amount of solvent. On incorporation of SNPs, the great enhancement in various properties likes surface roughness, and percentage swelling (1656% from 1100%) was observed. As an adsorbent, the synthesized nanocomposite was investigated with a tremendous hike in the dye removal efficiency on the incorporation of SNPs into the hydrogel network. The synthesized nanocomposite was found to remove 2.385 mg g⁻¹ of Brilliant green (BG) in 5 h whereas 1.56 mg g⁻¹ removal of Xylenol orange (XO) within 4 h. The higher values of K2 and closeness of theoretical and experimental adsorption capacity values at all the concentrations in both the dyes confirmed the adsorption kinetics data fitted well with pseudo-second order rate model. The correlation values (0.966 for BG and 0.995 for XO) and favourable RL (0.345 for BG and 0.263 for XO) of the adsorption data suggested better fit for Langmuir adsorption for both the dyes. Further, the negative values of ΔGo and ΔHo confirmed the adsorption of BG and XO dyes on the adsorbent is a feasible reaction. The reusability affinity of the synthesized SNP based nanocomposite up to 4 cycles outshine as a superior adsorbent material for the removal of cationic and anionic dyes from waste water.
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Adsorption of four dyes, namely methyl violet (MV), rhodamine 6G (R6G), acid chrome blue K (AK) and xylenol orange (XO) onto sodium alginate graft poly(acrylic acid-co-2-acrylamide-2-methyl-1-propanesulfonic acid)/kaolin (SA-g-P(AA-co-AMPS)/KL) hydrogel composite is studied. The factors influencing the adsorption capacities, including the initial concentrations of dye solutions, contact time, initial pH values and dosage of the adsorbent as well as ionic strength of the solution are discussed. It is more effective for the composite to adsorb cationic dyes such as MV and R6G rather than anionic dyes AK and XO. The maximum adsorption capacities of MV, R6G, AK and XO are 1361.1, 1627.8, 563.5 and 312.4 mg/g, respectively. The adsorption thermodynamics for the four dyes are in accordance with both the Freudlich and Redlich-Peterson equations. It is shown that adsorption of the cationic dyes R6G and MV is spontaneous, while that of anionic dyes AK and XO is not. The kinetics studies show that the adsorption of the four dyes fitted a pseudo-second-order equation.
In this study, color removal by absorption from synthetically prepared wastewater was investigated using montmorillonite clay by adsorption. As dyestuff Astrazon Red Violet 3RN (Basic Violet 16) was used. Experimental parameters selected were pH, temperature, agitation speed, initial dyestuff concentration, adsorbent dosage and ionic strength. It was established that adsorption rate increased with increasing pH, temperature, dye concentration and agitation speed, but decreased with increased ionic strength and adsorbent dosage. Adsorption equilibrium data obtained by a series of experiments carried out in a water bath were employed with common isotherm equations such as Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich. It was found that the Langmuir equation appears to fit the equilibrium data better than the other models. Furthermore, the fit of the kinetic data to common kinetic models such as the pseudofirst- order, second-order, Elovich and intraparticle diffusion models was tested to elucidate the adsorption mechanism. Kinetic data conformed to the pseudo-second-order model, indicating chemisorptions. In addition, the thermodynamic parameters activation energy, Ea, enthalpy ΔH*, entropy, ΔS*, and free energy change, ΔG*, were calculated. The values of the calculated parameters indicated that physical adsorption of ARV on the clay was dominant and that the adsorption process was endothermic.
Zeolite synthesized fro m cyclone ash (ZCA) was modified with various loadings of hexadecyltrimethylammonium bro mide (HDTMA-Br) and was used as adsorbent to remove Reactive Orange 16 (RO16), an azo reactive dye, from aqueous solution. The RO16 adsorption efficiencies for ZCA and surfactant-modified zeolites from cyclone ash (SMZCAs) were compared. SMZCAs presented higher RO16 adsorption efficiency than ZCA, and SMZCA with higher loading amount of HDTMA-Br exhibited higher RO16 adsorption efficiency. A series of experiments was conducted to examine the effects of contact time, solution pH, and adsorbent dosage on dye removal. The adsorption kinetic of RO16 onto adsorbents was discussed using the pseudo-first order, pseudo-second order and intra-particle diffusion models, and the pseudo-second order model provided the best correlation of the experimental data. The equilibriu m adsorption data were well represented by Langmuir isotherm model with maximu m adsorption capacity of 0.58 and 12.6 mg g-1 for ZCA and SMZCA, respectively.The toxicity tests of dye solutions before and after the adsorption treatment were evaluated with D. simlis and V.ficheri.
Biosorption of Acid Red 57 (AR57) on to Neurospora crassa was studied with variation of pH, contact time, biosorbent and dye concentrations and temperature to determine equilibrium and kinetic models. The AR57 biosorption was fast and equilibrium was attained within 40 min. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were applied to experimental equilibrium data for AR57 biosorption at various temperatures. The equilibrium data fitted very well to all the equilibrium models in the studied concentration range of AR57. Maximum biosorption capacity (qmax) of AR57 on to N. crassa was 2.16 × 10−4 mol g−1 at 20 °C. The kinetics of biosorption of AR57 were analyzed and rate constants were derived. The overall biosorption process was best described by a pseudo-second-order kinetic model. The changes in Gibbs free energy, enthalpy and entropy of biosorption were also evaluated for the biosorption of AR57 on to N. crassa. The results indicate that the biosorption was spontaneous and exothermic in nature. Copyright © 2006 Society of Chemical Industry
The incorporation of metal nanoparticles into polymers has resulted in the origination of a new class of materials that have found fascinating interest in biomedical, catalytic, optical and electronic as well as quantum‐size domain applications. This review article describes different strategies that have been adopted for the synthesis of metal nanocomposite materials with polymers and gel macromolecules (hydrogels and nanogels).
In the current study, a sustained release formulation made of natural polysaccharide tamarind kernel powder/kappa-carrageenan and (2-hydroxypropyl)-β-cyclodextrin (2-Hp-β-CD) was chosen to increase drug effectiveness. A kappa-carrageenan and tamarind kernel powder 3-D hydrogel network was synthesized with the aid of microwave irradiations. The ICs complexes were prepared using a physical mixture (PM), kneading (KM), and microwave (MW) approach and were then successfully loaded into the hydrogel. The synthesis of ICs was verified as a true IC using DSC, SEM, FTIR, ¹H NMR, and 2D NMR ROESY. A study on the in vitro sustained release of EV at pH 2, 7, and 7.4 was conducted at 37 °C. The microwave (MW) method was the most effective method for preparing true ICs of EV and 2-Hp-β-CD for sustained drug release, as evidenced by the drug release data, which indicated that PM and KM displayed a burst release of the drug. Ritger-Peppas and Peppas-Sahlin were essential models for drug release. A phase solubility analysis was done to evaluate the IC's stoichiometry and complexation constant. Studies on drug release have shown that 2-Hp-β-CD was effective at causing pH-responsive sustained drug release.
In this contribution, poly(maleic acid)-grafted cross-linked chitosan/montmorillonite composite nanospheres (PMAL-CTS/MMT) were synthesized via a facile approach for adsorption of organic dyes. The adsorption capacity of PMAL-CTS/MMT towards anionic acid yellow-17 (AY17) and cationic brilliant green (BG) was compared to PMAL-CTS, CTS/MMT, and MMT to emphasize the role of surface functional groups introduced by poly(maleic acid) and montmorillonite. Interestingly, the adsorption efficiency of PMAL-CTS/MMT nanocomposite towards both dyes in the single and binary systems was extremely high due to plenty of functional groups. The affinity of PMAL-CTS/MMT towards cationic and anionic dyes resulted from the feasible modulation of the surface charges as a function of the solution pH. The PMAL-CTS/MMT nanocomposite exhibited a maximum adsorption capacity of 518 and 1910 mg g–1 for AY17 and BG, respectively, which is higher than most of the adsorbents reported in recent literature studies. The proposed mechanism based on the characterization of PMAL-CTS/MMT after the adsorption highlights that the adsorption is mainly controlled by electrostatic interaction, π−π interactions, and hydrogen bonding. More importantly, the PMAL-CTS/MMT nanocomposite was successfully applied to separate the AY17 and BG dyes from real-life aquatic environments. Collectively, the simple fabrication and superior adsorption performance reveal that PMAL-CTS/MMT has the potential to treat concomitant organic dyes effectively.
Fabrication of adsorbents with excellent adsorption capacity, outstanding stability, easy separation ability, excellent recyclability and widely generality for organic dyes removal from wastewater remains challenging. Herein, three-dimensional polyaniline/poly(vinyl alcohol)/montmorillonite (PANI/PVAL/MMT) hybrid aerogels with easy separation performance and highly effective reusable adsorption on both anionic and cationic dyes were fabricated by a simple in-situ polymerization method. As-prepared hybrid aerogels were characterized via infrared spectra, Raman spectra, scanning electron microscopy, energy dispersive spectra mapping, small and wide-angle X-ray scattering, thermogravimetric analysis, mercury intrusion porosimetry and elemental analysis. The results showed that MMT particles were successfully incorporated into aerogel matrix. Well-defined hierarchical structure, where PANI nanofibers are coated on the skeleton wall, can be observed for PANI/PVAL/MMT when the incorporation amount of MMT was around 11.1 wt%. The adsorption performance of as-prepared hybrid aerogels on both anionic and cationic dyes was systemically carried out at different solution pH, adsorbent dosage and initial dye concentration. The data analysis showed that the adsorption process for PVAL/PANI/MMT aerogel for Reactive Black 5, methyl orange and safranin followed Freundlich isotherm and the maximum experimental adsorption capacities were found to be 199, 251 and 57.0 mg g−1 at 25 °C, respectively. Mechanism studies indicated that the electrostatic interaction is the main driving force for the adsorption of dyes. The results demonstrated that the fabricated hybrid aerogel is an efficient adsorbent for the removal of both anionic and cationic organic dyes.
Copolymer of acrylic acid (AA) and itaconic acid (IA) grafted onto sodium carboxymethyl cellulose hydrogel (CMC-g-poly (AA-co-IA)) was successfully synthesized as an adsorbent to remove safranin-O from wastewater. The swelling and removal efficiencies of CMC-g-poly (AA-co-IA) were enhanced by increasing IA/AA molar ratio as well as by incorporation of montmorillonite clay nano-sheets (MMT). The surface area of MMT, CMC-g-poly (AA-co-IA), and CMC-g-poly (AA-co-IA) samples was 15.632, 0.61452, and 0.66584 m²/g, respectively, indicating the effectiveness of MMT nano-sheets in improving hydrogel surface area. The maximum removal efficiency of CMC-g-poly (AA-co-IA)/MMT under optimum conditions i.e., pH of 8, initial concentration of 10 mg/L, adsorbent dose of 2 g/L, and contact time of 40 min was ascertained 99.78% using a response surface methodology-central composite design (RSM-CCD). Pseudo-second-order and Langmuir models giving the maximum monolayer adsorption capacity of 18.5185 mg/g and 19.1205 mg/g for CMC-g-poly (AA-co-IA) and CMC-g-poly (AA-co-IA)/MMT samples, respectively are the best-fitted models for kinetic and equilibrium data. Thermodynamically, safranin-O decontamination was spontaneous, exothermic, and entropy decreasing. Moreover, ad (de)sorption behavior study showed that CMC-g-poly (AA-co-IA)/MMT performance was not changed after multiple recovery steps. Therefore, CMC-g-poly (AA-co-IA)/MMT was considered as a highly potential adsorbent for safranin-O removal from wastewater.
In this study, Montmorillonite nanosheet/poly(acrylamide-co-acrylic acid)/sodium alginate hydrogel beads with high handle capacity towards dyes effluent was investigated. Montmorillonite nanosheet cooperated with acrylamide and acrylic acid via hydrogen bond, amidation and polymerization interaction first, then crosslinked with sodium alginate by intertwining interaction to form 3D network structure, achieving free entrance and rapid adsorption for dye molecules. Batch adsorption tests revealed a multilayer and heterogeneous adsorption of methylene blue (MB) onto hydrogel beads according to pseudo two-order kinetic model and Freundlich isotherm model. The adsorption capacity of MB was controlled by the amount of adsorption sites in hydrogel beads, which could reach maximum of 530.7 mg/g. The adsorption mechanism is attributed to Ca ion-exchange and chemical bonding of COOH and OH groups with MB. Column tests showed an excellent dynamic adsorption performance of hydrogel beads towards MB wastewater compared with the traditional commercial adsorbents of granular active carbon and cation exchange resin, which achieved 380 bed volume (BV) of treated sewage to meet the emission standards using the single column. Moreover, 1625 BV and more treated dye effluent was achieved to be safety discharged via double column series in 5 circulation-regeneration, indicating the great potential of hydrogel beads in practical application. Such hydrogel realized the performance promotion of macromolecule polymers and nanoclay in materials design, and green application in water treatment.
The objective of the study is to enhance the aqueous solubility and stability of edaravone, a free radical scavenger drug. Inclusion complexes of edaravone with β-cyclodextrin were prepared by microwave irradiation and physical mixture method and confirmation of inclusion complexes were investigated by different analytical techniques such as FT-IR, ROESY, DSC, and ¹H NMR. pH-sensitive nanocomposites based on chitosan (CH), sodium alginate (ALG), and bentonite (BN) were synthesized. To get the maximum percentage swelling different reaction parameters that are responsible for the synthesis of the nanocomposite were optimized and characterized by various techniques such as FESEM, EDS, XRD, and FT-IR. To regulate the drug delivery, inclusion complexes were directly loaded into the CH/ALG hydrogel, and CH/ALG/BN nanocomposite and release studies were evaluated at different pH environments. The solubility of edaravone was investigated by phase solubility and the graph results in a typical AL type behavior, suggesting the formation of a 1:1 stoichiometry inclusion complex. The comparative evaluation of drug release was explored by kinetic models. Controlled release of drug was achieved from CH/ALG/BN nanocomposite in comparison to CH/ALG hydrogel. The exploratory kinetic investigation revealed that β-CD plays a critical role in the drug release process by influencing polymer relaxation, resulting in slow release.
The aim of present work to prepare inclusion complexes of amlodipine besylate (APB) drug and β-Cyclodextrin
(β-CD) by microwave and kneading method for sustain release of drug. Microwave irradiation completes the
process in very short time and is more environmentally benevolent method. The complexation of APB with β-CD
was characterized by 1
H NMR and XRD. A nanocomposite was synthesized by incorporating the graphene oxide
(GO) in the polymer network of chitosan (CH) and sodium alginate (ALG) under microwave conditions. Poor
loading of drugs in traditional drug delivery was improved by introducing inclusion complexes (ICs) directly into
the nanocomposite. The operation parameters like ratio of backbones, time, amount of solvent, amount of
graphene oxide and pH were optimized by response surface methodology (RSM) in order to obtain maximum
percentage swelling. From normal plot and pareto chart it was found that ratio of backbones, amount of GO and
solvent are the optimized variables. Furthermore, to get most optimized variables central composite design
(CCD) was analyzed. The ICs were directly loaded into the nanocomposite and their release kinetics was studied
by six kinetic models under different pH at 37 ◦C. The preparatory kinetic analysis, acknowledge that the
cyclodextrin affects the relaxation rate of nanocomposite, leading to slower release of drug.
Hydrogels are the most iconic class of soft materials and since their first report in the literature has attracted the attention of uncountable researchers. Over the past two decades, hydrogels become smart and sophisticated materials with plenty of applications possibilities. The biomedical research area has demonstrated a particular interest in hydrogels since they can be engineered from different polymers and due to their tunable properties. Moreover, hydrogels engineered from polymers extracted from biorenewable sources have been popularized in biomedical usages, as they are low-toxic, eco-friendly, biocompatible, easily accessible, and inexpensive at the same time. However, the multifaceted challenge is to find an ideal plant green hydrogel in the tissue engineering that can mimic critical properties of human tissues in terms of structure, function, and performance. In addition, these natural polymers are also idealized to be conveniently functionalized so that their chemical and physical behaviour can be manipulated for drug delivery and stem cell-guided tissue re-generation. Here, the most recent advances in the synthesis, fabrication and application of plant green hydro-gels in biomedical engineering are reviewed. It covers essential and updated information about plant as green sources of biopolymers to be used in hydrogel synthesis, general aspects of hydrogels and plant green hy-drogels and a substantive discussion regarding the use of such hydrogels in the biomedical engineering area. Furthermore, this review addresses and detail the present status of the field and, also, answer several important questions about the potential use of plant green hydrogels in advanced biomedical applications including therapeutic, tissue engineering, wound dressing, diagnostic, etc.
In this study, carboxymethyl cellulose based graft poly(acrylamide) hydrogel (CMC-g-P(AAm)) and its nanocomposite with montmorillonite (CMC-g-P(AAm)/MMT) were produced by the free radical method and it was used to malachite green (MG) dye removal from aqueous solution. The properties and characterization of the adsorbents were investigated using FTIR, SEM, TGA, and XRD analyzes, and the results showed that MMT nanoparticles were successfully distributed in the hydrogel system. MMT nanoparticles were loaded into the hydrogel system with different weight percentages and the maximum adsorption efficiency of MG dye was determined at 10 wt% MMT. Also, the effect of temperature, contact time, initial concentration of MG dye and initial pH on the adsorption efficiency of MG dye was studied in a batch. Equilibrium behavior investigation of the adsorption process showed that the equilibrium data determined are in good agreement with the Langmuir isotherm model and the monolayer surfaces play an effective role in the adsorption process. The maximum monolayer adsorption capacity (qmax) determined using the Langmuir isotherm model for CMC-g-P(AAm) and CMC-g-P(AAm)/MMT were determined to be 158.1 mg/g and 172.4 mg/g, respectively. Also, the kinetic study showed that the pseudo-second- order kinetic model is more capable of describing the kinetic behavior of the process than other models. Also, the α parameter values for the MG dye adsorption process using CMC-g-P(AAm) and CMC-g-P(AAm)/MMT were determined to be 0.6337 mg/g·min and 31.04 mg/g·min, respectively. This indicates that the produced composite has a high adsorption value. Gibbs free energy (ΔG°) was negative for the adsorption processes in the range of 25–50 °C, indicating that the process was spontaneous. In addition, the enthalpy parameter (ΔH°) was determined for the adsorption process using CMC-g-P(AAm) and CMC-g-P(AAm)/MMT nanocomposite hydrogels at 39.859 KJ/mol and 74.736 KJ/mol, respectively. Positive ΔH° indicates that the process is endothermic in the range of 25–50 °C using both adsorbents. Also, the concentrations effect of Na+ and K+ ions on adsorption efficiency was investigated and it was concluded that the efficiency of the adsorption process decreased with the increase of ions concentration. Adsorption efficiency decrease can be due to the occupation of active sites and repulsive electrostatic interactions at the adsorbent surface with the MG dye molecule.
For the first time, stable LBG-cl-Poly(DMAAm) hydrogel is prepared via free radical in situ polymerization of N, N-dimethyl acrylamide by employing N, N'-methylene bis(acrylamide) as cross-linkers. The hydrogel was characterized by different physicochemical techniques like equilibrium swelling percentage, point of zero charges (pHPZC), FTIR, SEM, and TGA. The LBG-cl-Poly(DMAAm) hydrogel was used in experiments on swelling behavior and adsorption of water-soluble cationic dye-Brilliant green (BG). The influence of pH on the structural change of BG dye was discussed. The swelling of hydrogel was sensitive toward the pH, ionic strength, and temperature stimuli. Adsorption behavior of hydrogel was investigated for the adsorption of BG dye and it was found to highly efficient in removing 97.7% of BG dye in 50 mg L-1 of dye solution. Adsorption data displayed that the adsorption of BG followed the pseudo-second-order kinetic model (R2 = 0.998) and Langmuir isotherm model (R2 = 0.988) with a maximum adsorption capacity of 142.85 mg g-1. The developed LBG-cl-Poly(DMAAm) hydrogel demonstrated efficient separation of BG dye and maintained maximum adsorption capacity after 6th regeneration cycles. The results indicated that LBG-cl-Poly(DMAAm) hydrogel can be used as an alternative and promising adsorbent to be applied in the treatment of effluents containing the BG dye.
This research paper reports the feasibility of utilizing zeolite-Y incorporated hydrogel composite (ZHC) of gum karaya (GK) as a potential adsorbent to treat cationic dyes contaminated wastewater. Initially, the crosslinked hydrogel of GK with N-isopropylacrylamide (NIPAM) and acrylic acid (AA) was synthesized via grafting and subsequently zeolite-Y particle were homogeneously dispersed thought-out the polymer matrix. Changes in the property profile of parental hydrogel polymer after incorporating zeolite-Y were studied using SEM, X-ray diffraction, FTIR and TEM techniques. For dye adsorption studies, brilliant green dye (BG) was taken as the target pollutant. Adsorption isotherm followed Langmuir model with 1461.35 mg/g adsorption capacity and the adsorption kinetics was most appropriately explained using pseudo-second-order model. Diffusion of dye molecules into the internal structure of ZHC was governed collectively by intraparticle and liquid film diffusion mechanisms. Furthermore, ZHC was regenerated and applied six times repeatedly to adsorb dye without much alteration in the performance.
The purpose of the present study is to synthesise a self assembled nanocomposite by incorporating GO nanosheets into the polymer network of carboxy methyl cellulose and chitosan without using any initiator and cross-linker system. By incorporation of GO nanosheets, a great enhancement in various properties likes surface roughness, percentage swelling (from 2347% to 4633.8%) and adsorbent properties. The nanocomposite samples were investigated for removal of various kinds of dyes from waste water sources and were found highly selective for different cationic dyes. The adsorbent showed 97.9% removal of BG in 7 h whereas 100% removal of MB in just 1.5 h. The adsorption kinetics statistics fitted well in pseudo-second order rate equation. The correlation values and favourable RL of adsorption data suggested better fit for Langmuir adsorption for both the dyes.
In this study, nanoscale zero-valent iron (nZVI) supported on layered double hydroxide (LDH) composite ([email protected]) was prepared, characterized and applied to U(VI) scavenging in water. Removal of U(VI) as a function of pH, ionic strength, reaction time, initial concentrations of U(VI), and temperature were studied and compared with pure LDH and nZVI, the [email protected] had best U(VI) removal efficiency owning to the excellent synergistic combination of LDH adsorption and nZVI reduction. XPS analysis found that surface oxygen functional groups and surface-bound Fe(II) played a critical role in U(VI) remediation. The large surface areas (334.0 m²/g), abundant functional groups (i.e., M–O, C–O and –OH), rapid kinetics (adsorption equilibrium within 1 h) and excellent adsorption capacities (176 mg/g) indicating that [email protected] can be considered as a potential material for preconcentration of U(VI) from sewage water.
This work explored the potential of magnetic sawdust carbon nanocomposites for cationic dyes removal from aqueous medium. EDTA modified magnetic sawdust carbon nanocomposites ([email protected] 3 O 4 /SC ncs) were prepared by biogenic green reduction and precipitation approach. The surface properties, structure and composition of nanocomposites were characterized by HRTEM, FESEM, XRD, EDX, BET, FTIR etc. The Fe 3 O 4 nanoparticles were 10–20 nm in diameters and having 14 m ² /g surface area. Removal of Methylene blue (MB) and Brilliant green (BG) dyes from aqueous medium was studied in batch mode experiments. The maximum removal was achieved at neutral pH 7.0 with in 30 min. Adsorption capacity of [email protected] 3 O 4 /SC for MB and BG dyes was 227.3 mg/g and 285.7 mg/g, respectively. Dye adsorption behaviour is well explained by Freundlich model. The rate of cationic dye adsorption is explained by pseudo-second order model. The value of thermodynamic parameters confirmed that adsorption process was spontaneous and favourable. Desorption and reusable efficiency of nanocomposites was also evaluated.
A new adsorbent (amphoteric adsorbent coating: AAC) based on composite coating with amphoteric functionality was employed to study the adsorption mechanism of Brilliant Green (BG) and Acid Red 1 (AR1) dyes. This adsorbent was prepared as a coating and supported on cotton cloth by application of a facile method, based on the combined use of smectite-based clay powder, acrylic polymer emulsion (APE) and cationic polyelectrolyte. The novel adsorbent coating was characterized by FE-SEM, EDX, zeta potential and FTIR analysis. Subsequently, the equilibrium adsorption isotherms of AR1 and BG dyes were performed and analyzed at different temperatures (from 303 to 343 K) in order to achieve a thorough comprehension of dyes adsorption mechanism. To this aim, a multilayer model with saturation was developed using statistical physics theory and was applied as a sophisticated tool for data interpretation. The correlations of experimental and theoretical results allowed to understand two distinct behaviours for the adsorption of AR1 and of BG dyes, which were related to the formation of two different adsorbed layers and a variable number of layers, respectively. Based on the parameter of the adopted model, the adsorption geometry of dyes has been described at different temperatures. Interestingly, the adsorption process was energetically typified by estimation of the adsorption energies, which indicated that the adsorption of AR1 and BG dyes were exothermic and endothermic, respectively.
The toxicity and radioactivity of uranium (235,238U(VI)) result in serious environmental issues in recent years. The polyethyleneimine decorated waste fly ash (FA@PEI) from thermal power plant was fabricated via a novel and cost-efficient method and applied for the U(VI) elimination from aqueous solutions by batch experiments. According to experiment results, U(VI) removal was dramatically influenced by pH value and ionic strength-independent, which indicated that the interaction was primarily controlled by inner-sphere surface complexation. Kinetic studies showed that FA@PEI had an ultrafast removal rate (1.5 h to achieve adsorption equilibration) for U(VI) and the pseudo-second-order model well fitted the adsorption process. The maximum removal capacity of U(VI) on FA@PEI was 70.3 mg•g-1 at 298 K and pH 5.0. Based on the thermodynamics data (ΔH0> 0, ΔS0> 0 and ΔG0< 0), U(VI) removal process was typical spontaneous and endothermic. According to the XPS analysis, the enhanced U(VI) adsorption was mainly attributed to the abundant metal-oxide bonds and amine groups (-NH2, -NH-). Furthermore, the FA@PEI material also exhibited outstanding regenation ability. This paper highlights the FA@PEI as an environmental friendly and economical material for the U(VI) elimination from waste water.
The magnetic composite-materials (Fe3O4@[email protected]) were prepared by sodium dodecyl benzene sulfonate (SDBS) modified layered double hydroxides ([email protected]) with Fe3O4 via co-precipitation method. The results of XRD, FT-IR and SEM/EDS indicated that the dispersibility of LDHs was improved, and the modification of SDBS took place on the surface of LDHs. The adsorption capacity of Fe3O4@[email protected] to brilliant green (BG) reaches 329.1 mg/g after the adsorption equilibrium. The thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous, and the rate of a reaction increased with the raise of the reaction temperature. The Langmuir model was applicable for describing the sorption isotherms, indicating that the adsorption process is a monolayer adsorption. The results of kinetics study showed that adsorption fitted the pseudo-second order model well. The adsorbents still have good adsorption performance after four adsorption cycles. Moreover, the magnetic composite could be easily separated from aqueous solution. This indicated that Fe3O4@[email protected] can be considered as potential adsorbents in environmental applications for the removal of BG from aqueous solutions.
Well-dispersed graphene oxide sheets were successfully incorporated into a superabsorbent resin through in situ graft polymerization of acrylic acid on carboxymethyl cellulose backbone in the presence of graphene oxide as filler. The structure and properties of the resultant superabsorbent resin were studied in detail by means of a variety of characterization methods. The influence of the feed ratio of starting materials (such as GO, initiator, cross-linker, the ratio of CMC to AA and the neutralized degree of AA) and pH values on water absorbency and retention ability was extensively determined and discussed. The obtained results showed that the introduction of graphene oxide had no obvious influence on the inherent structure of the superabsorbent resin but changed the surface morphology significantly. Importantly, the hybrid superabsorbent resin showed an enhanced thermal stability and remarkably improved swelling ratio as well as water-retention ability comparing with that of the pure superabsorbent resin.
Cationic cellulose hydrogels (CCGs) were prepared from quaternized celluloses with degrees of substitution (DS) of 0.56, 0.84, and 1.33, by the cross-linking reaction with poly(ethylene glycol) diglycidyl ether as a cross-linker. The CCGs exhibited swelling behavior in aqueous solutions, which was not affected by pH and temperature of the solution because of the presence of quaternary ammonium groups in their structures. The CCGs showed adsorption ability toward anionic dyes in aqueous solution, which increased with increasing DS. The dye adsorption was found to follow the pseudo-second order kinetic model and the equilibrium isotherm data can be described by the Langmuir adsorption model. In addition, the CCGs could be regenerated and proved to be recyclable adsorbents for wastewater treatment.
A novel dual functional microsphere adsorbent of alginate/carboxymethyl cellulose sodium composite loaded with calcium and aluminum (SA/CMC-Ca-Al) is prepared by injection device to remove fluoride and uranium, respectively, from fluoro-uranium mixed aqueous solution. Batch experiments are performed at different conditions: pH, temperature, initial concentration and contact time. The results show that the maximum adsorption amount for fluoride is 35.98 mg/g at pH 2.0, 298.15 K concentration 100 mg/L, while that for uranium is 101.76 mg/g at pH 4.0, 298.15 K concentration 100 mg/L. Both of the adsorption process could be well described by Langmuir model. The adsorption kinetic data is fitted well with pseudo-first-order model for uranium and pseudo-second-order model for fluoride. Thermodynamic parameters are also evaluated, indicating that the adsorption of uranium on SA/CMC-Ca-Al is a spontaneous and exothermic process, while the removal of fluoride is non-spontaneous and endothermic process. The mechanism of modification and adsorption process on SA/CMC-Ca-Al is characterized by FT-IR, SEM, EDX and XPS. The results show that Ca (II) and Al (III) are loaded on SA/CMC through ion-exchange of sodium of SA/CMC. The coordination reaction and ion-exchange happen during the adsorption process between SA/CMC-Ca-Al and uranium, fluoride. Results suggest that the SA/CMC-Ca-Al adsorbent has a great potential in removing uranium and fluoride from aqueous solution.
Pectin–thorium (IV) tungstomolybdate (Pc/TWM) nanocomposite was prepared by mixing biopoly-mer pectin with its inorganic counterpart thorium (IV) tungstomolybdate (TWM) using the sol–gel method. The nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Distribution coefficient, thermal stability, pH titrations, elution and concentration behaviour were investigated to explore the ion exchange behaviour of nanocomposite material. Pc/TWM exhibited higher ion exchange capacity (1.10 mequiv/g) than its inorganic counterpart (0.62 mequiv/g). The Pc/TWM nanocomposite ion exchanger was thermally stable as it retained 59% of its ion exchange capacity upto 400 • C. The pH titrations study revealed the bifunctional nature of Pc/TWM. Inorder to explore the environmental applicability of the Pc/TWM nanocomposite material, its antibac-terial and photocatalytic activities was investigated. 76% of methylene blue dye was photocatalytically degraded after five hours exposure. It also totally inhibited Escherichia coli at 400 g/ml concentration of Pc/TWM nanocomposite.
Adsorptive uptake of methylene blue (MB) by both raw and modified Ball clay (MBC) were investigated through batch adsorption experiment. Modification of the raw clay was done by acid treatment, cation exchange and calcination; the raw and modified clays were molded into beads and freeze dried. Brunauer Emmett Teller (BET), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared spectroscopy (FTIR) analysis were carried out on both clays. The mesoporous modified Ball clay (MBC) had percent increase of adsorption capacity and surface area of 188.60% and 820%, respectively than the raw Ball clay (RBC). Langmuir, Freundlich and Redlich–Peterson models were used to obtain isotherm parameters. Pseudo-second-order kinetic model described the adsorption processes which were more favorable at higher pH. Increase in temperature from 30 to 50 °C of MB adsorption on both RBC and MBC increased the degree of dispersion and the process was found to be physiosorptive, endothermic and spontaneous for MBC but non-spontaneous for RBC; this was obtained from the thermodynamic studies. The results showed that MBC can be used adequately to adsorb MB more efficiently than RBC.
Locally sourced clay was harnessed to study its adsorptive potential of methylene blue (MB) in wastewater streams. The clay was modified with sulfuric acid and aluminum hydroxide. The raw and modified freeze dried clay bead RHC and MHC were subjected to batch and batch/fixed-bed adsorption studies, respectively. Elemental analysis, morphological structures were determined, and surface area of 19.3 (RHC) and 101.2 (MHC) m2/g were obtained. Langmuir, Freundlich and Redlich–Peterson isotherms models were analyzed and the modification increased adsorption capacity from 58.02 to 223.19 mg/g at 30 °C. The MB adsorption on RHC/MHC was spontaneous, exothermic and obeyed pseudo-second-order model.
A series of superabsorbent hydrogel based on carboxymethylcellulose (CMC) and polyvinylpyrrolidone (PVP) crosslinked with gamma irradiation have been proposed for agriculture application. The effect of preparation conditions such as feed solution composition and absorbed irradiation dose on the gelation and swelling degree was evaluated. The structure and the morphology of the superabsorbent CMC/PVP hydrogel were characterized using Fourier transform infrared spectroscopy technique (FTIR), and scanning electron microscope (SEM). Effect of ionic strength and cationic and anionic kinds on the swelling behavior of the obtained hydrogel was investigated. Urea as an agrochemical model was loaded onto the obtained hydrogel to provide nitrogen (N) nutrients. The water retention capability and the urea release behavior of the CMC/PVP hydrogels were investigated. It was found that, the obtained CMC/PVP hydrogels have good swelling degree that greatly affected by its composition and absorbed dose. The swelling was also extremely sensitive to the ionic strength and cationic kind. Owing to its considerable slow urea release, good water retention capacity, being economical, and environment-friendly, it might be useful for its application in agriculture field.
Experiments were carried out to remove brilliant green dye by adsorption technique using a novel adsorbent (activated carbon prepared from acorn). The prepared adsorbent was characterized by BET surface area measurement, FTIR, SEM and elemental analysis. Various parameters such as initial dye concentration, adsorbent dose, initial pH and temperature were studied to observe their effects on the dye adsorption process. At optimum values of the above mentioned parameters, more than 90% removal efficiency was obtained within 30 min at adsorbent dose of 2 g/100 mL for initial dye concentration of 25 mg/L. The percentage of dye removal remains almost constant within the pH range of around 6–10. The adsorption of dye was found to follow a pseudo-second-order rate equation. Intra particle diffusion model was studied in order to determine the rate limiting step of the adsorption process. Langmuir isotherm model was fitted the best for the adsorption system with an adsorption capacity of 2.11 mg/g of adsorbent. The present adsorbent may be considered as an alternative adsorbent for the better performance of the brilliant green dye removal from its aqueous medium.
Pectin-thorium (IV) tungstomolybdate (Pc/TWM) nanocomposite was prepared by mixing biopolymer pectin with its inorganic counterpart thorium (IV) tungstomolybdate (TWM) using the sol-gel method. The nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Distribution coefficient, thermal stability, pH titrations, elution and concentration behaviour were investigated to explore the ion exchange behaviour of nanocomposite material. Pc/TWM exhibited higher ion exchange capacity (1.10mequiv/g) than its inorganic counterpart (0.62mequiv/g). The Pc/TWM nanocomposite ion exchanger was thermally stable as it retained 59% of its ion exchange capacity upto 400°C. The pH titrations study revealed the bifunctional nature of Pc/TWM. Inorder to explore the environmental applicability of the Pc/TWM nanocomposite material, its antibacterial and photocatalytic activities was investigated. 76% of methylene blue dye was photocatalytically degraded after five hours exposure. It also totally inhibited Escherichia coli at 400μg/ml concentration of Pc/TWM nanocomposite.
Macroporous temperature-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels have been successfully synthesized by using poly(ethylene glycol) (PEG) as the pore-forming agent. Scanning electron microscope graphs reveal that the macroporous network structure of the hydrogels can be adjusted by applying different molecular weights of PEG during the polymerization reaction. The surface roughness of the hydrogels is also investigated using atomic force microscopy, and the results indicate that the surface of the PEG-modified gel is much rougher compared to that of the conventional PNIPAAm gel. The newly invented macroporous hydrogels exhibit much better properties as temperature-sensitive intelligent polymers. For instance, at a temperature below the lower critical solution temperature (LCST), they absorb larger amounts of water and show obviously higher equilibrated swelling ratios in the aqueous medium. Particularly, due to their unique macroporous structure, the PEG-modified hydrogels show a tremendously faster response to the external temperature changes during deswelling and reswelling processes as the temperature cycles across the LCST. They can also shrink and lose water with dramatically rapid rates at temperatures above the LCST. The macroporous PNIPAAm gel has potential applications in controlled release of macromolecular active agents.
The objective of this study was to assess the suitability and efficiency of activated carbon (AC) and multiwalled carbon nanotube (MWCNT) for the removal of Eriochrome Cyanine R (ECR) molecules from aqueous solutions. The effect of different variables in the batch method as a function of solution pH, contact time, initial dye concentration, AC and MWCNT amount, temperature, electrolyte, and so forth by the optimization method has been investigated. ECR contents were determined using a UV–vis spectrophotometer before and after ECR adsorption on the AC and MWCNT, and the removal percentage was calculated using the difference in absorbance. The sorption processes followed the pseudosecond order in addition to intraparticle diffusion kinetics models with a good correlation coefficient with the overall entire adsorption of ECR on both adsorbents. Equilibrium data fit well with the Langmuir and Tempkin models with a maximum adsorption capacity based on the Langmuir equation of (40.6 and 95.2) mg·g–1 for AC and MWCNT, respectively. Thermodynamic parameters such as change in enthalpy (ΔH°) and entropy (ΔS°), activation energy (Ea), sticking probability (S*), and Gibbs free energy changes (ΔG°) were also calculated. Judgment based on the obtained results of thermodynamic values shows the spontaneous and endothermic nature adsorption processes on both adsorbents.
Adsorption of a basic dye, safranin, from aqueous solutions onto activated carbon prepared from corncobs (ACCC) has been investigated. Various experiments have been carried out using batch adsorption technique to study the effects of the process variables, which include initial pH, adsorbent dosage, initial dye concentration, particle size, temperature, and agitation speed, on the adsorption process. The adsorption of safranin onto the adsorbent was found to improve with the increase in adsorbent dosage and finer mesh size. Maximum adsorption was observed at pH > pHzpc in the pH values ranging from 5 to 9. It was observed that the rate of adsorption improves with increasing temperature and the process is endothermic with an ΔH value of 35.698 kJ/mol. The kinetics followed is first order in nature. The results showed that both Langmuir and Freundlich isotherms fit the equilibrium data. Also, the results revealed that activated carbon from corncob, an agricultural waste biomass, proved to be an excellent low-cost sorbent.
The present study explored the adsorptive characteristics of Brilliant Green dye from aqueous solution onto NaOH treated saw dust of Indian Eucalyptus wood, a timber industry waste. Batch studies were performed to evaluate the influence of various experimental parameters like initial pH, contact time, adsorbent dose, initial concentration and temperature on the removal of Brilliant Green. Optimum conditions were found to be initial pH = 2.9, contact time = 3 h and adsorbent dose = 4 g/l. The pseudo-second-order kinetic model represented the adsorption kinetics of Brilliant Green onto NaOH treated saw dust. Equilibrium isotherms were analyzed by Freundlich, Langmuir, Redlich–Peterson and Temkin isotherm models using non-linear regression technique. NaOH treated saw dust which was used showed surface area = 0.3742 m2/g, pore volume = 0.00836 cm3/g and average pore diameter = 893.6 A0. Adsorption of Brilliant Green onto NaOH treated saw dust is favorably influenced by decrease in the temperature of the operation. Thermodynamics showed that the Brilliant Green adsorption was most favorable onto NaOH treated saw dust.Research Highlights►Adsorption kinetics was found to follow a second-order rate expression. ►Isotherm data for Brilliant Green on saw dust fitted the R–P and Temkin isotherms. ►The adsorption was found to be exothermic in nature. ►The negative value of Gibbs free energy change indicates spontaneous adsorption. ►Saw dust could be employed as low-cost adsorbent for removal of Brilliant Green.
This paper aims to review the problem of colour in textile effluents, the different classes of dyes available and their contribution to the problem. Through new regulations, pressure is being placed on water companies all over the world to reduce the amount of colour in sewage effluent. Dyes exhibit low toxicity to mammals and aquatic organisms and therefore colour consents are normally applied for aesthetic and industrial reasons rather than for prevention of toxicity. The absorbance, ADMI values and concentrations of dyes in effluent are examined here with particular reference to reactive azo dyes used in cotton processing. Colour consents, the problem of colour in textile wastewaters and the importance for research in this area are also discussed. Dye concentrations of 0.01 g dm−3 up to 0.25 g dm−3 have been cited as being present in dyehouse effluent, depending on the dyes and processes used. ADMI values ranged from 50 to 3890 units for the dyeing of cotton. It was concluded that 1500 ADMI units was a reasonable value to aim for when simulating coloured effluents. Simulated textile effluents may be used for research purposes. These should resemble real wastes as closely as possible, but it is often difficult to replicate the ADMI values, absorbance and spectra of real effluents. The concentrations of dye used in simulated effluents examined in literature varied from 0.01 g dm−3 to 7 g dm−3. As absorbance and ADMI values change with the types of dye used, it is difficult to relate these values to dye concentrations. A concentration of 0.18 g dm−3 of a Red or Yellow dye or 0.43 g dm−3 of a blue dye would provide an ADMI of approximately 1500 units and fits within the range of dye concentrations presented in literature. A dye mixture simulating colour in a real textile effluent is suggested and some limitations of simulating actual wastewaters discussed.© 1999 Society of Chemical Industry