Development of a novel bionanocomposite of UiO-66/xanthan gum/alginate crosslinked by calcium chloride for azo dye removal: Insight into adsorption kinetics, isotherms, and thermodynamics.

In the present work, UiO-66/xanthan gum/alginate bionanocomposite adsorbent was fabricated using the in-situ crosslinking-gelation method, characterized by different techniques, and finally used for the removal of methylene blue dye from aqueous solution. Adsorption studies were performed using batch experiments and the influencing operational parameters such as contact time, initial pH solution, temperature, initial dye concentration, adsorbent dose, pHPZC, swelling, regeneration, and reuse of the adsorbent were investigated. The various kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion) and isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) were used to analysis of the experiment results. The results were best fitted to the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of dye on the adsorbent was obtained at 9.96 mg/g at pH = 11. The value of pHPZC for the adsorbent was obtained at about 8. According to thermodynamic parameters, the dye adsorption was found as spontaneous and endothermic due to the negative value of the ΔG° and ΔH°. After 4 times of reusability cycles, the adsorption efficiency remained above 86 %, which represented a certain regeneration ability. As a result, this research indicates that UiO-66/xanthan gum/alginate bionanocomposite can be utilized as a promising bio-adsorbent for azo dye removal from contaminated wastewater.

A polyurethane foam membrane filled with double cross-linked chitosan/carboxymethyl cellulose gel and decorated with ZSM-5 nano zeolite: Simultaneous dye removal.

A novel bio-based polyurethane foam was fabricated using double cross-linked chitosan/carboxymethyl cellulose gel, filled with ZSM-5 nano zeolite, and hot-pressed into the membrane. The prepared foam membrane was characterized using FESEM, FTIR, BET, TGA, and pHZPC analyses and then used for continuous dye removal. The results modification of polyurethane foam with chitosan/carboxymethyl cellulose gel and ZSM-5 nano zeolite would increase the retention ability of positive cationic methylene blue. Also, the foam could simultaneously remove methyl orange, eriochrome black T, and methylene blue from the binary and trinary solutions but could effectively be used to selectively removal methylene blue. In addition, the dye removal ability at the breakthrough was enhanced with decreasing flow rate, and increasing bed height, pH, initial dye concentration, and nano zeolite content in the foam. To describe the breakthrough curves different models were utilized which best fits were obtained with Modified Dose-Response as compared to Thomas, Adams & Bohart, Yoon-Nelson, and Wolborska models.

Fabrication of Zn-based magnetic zeolitic imidazolate framework bionanocomposite using basil seed mucilage for removal of azo cationic and anionic dyes from aqueous solution.

The Basil seeds mucilaginous polysaccharide exhibits remarkable physical and chemical properties like high water-absorbing capacity, emulsifying, and stabilizing properties. The metal-organic frameworks are one of the most promising precursors made of metal clusters and organic connectors for the fabrication of advanced adsorbents due to their unique properties. In this study, the bionanocomposite of magnetic zeolitic imidazolate framework-8 was successfully synthesized and applied to adsorb azo cationic and anionic dyes. The synthesized magnetite nanoparticles were pretreated with mucilage extracted from basil seeds to acquire negatively charged magnetite surface, followed by nucleation through attracting zinc cation, and then the growth of metal-organic frameworks which yields high-quality ZIF-8 crystals. The samples were characterized by Field Scanning Electron Microscopy, X-ray Diffraction, Fourier Transform Infrared Spectrometry, vibrating sample magnetometer, and Brunauer-Emmett-Teller surface area analysis. In the process of adsorption, influencing factors and recycling regeneration were discussed, and the adsorption mechanisms such as kinetics, isotherm, and thermodynamics were explored. The results of the adsorption process showed that maximum adsorption capacities were 9.09 and 13.21 mg/g for Methylene blue and Eriochrome Black T, respectively. The excellent reusability combined with its magnetic separation property makes the nanocomposite a promising adsorbent for the removal of cationic and anionic dyes.

Lignin extraction from barley straw using ultrasound-assisted treatment method for a lignin-based biocomposite preparation with remarkable adsorption capacity for heavy metal.

In this study, lignin was extracted using ultrasonic and then, by the gelation-solidification method, the extracted lignin was used as reinforcement for the synthesis of a novel biocomposite as biosorbent for removal of lead heavy metal from aqueous solutions. The structural and chemical characteristics of biocomposite were determined by FESEM, EDX, FTIR, and BET analyses, respectively. Biocomposite beads were used as an efficient adsorbent in the lead removal process from aqueous solutions in different conditions. Also, point zero charge studies and the effective parameters on adsorption such as contact time, pH, temperature and initial concentration, kinetics, isotherms, and thermodynamics of the adsorption, and adsorbent regeneration and reuse were investigated. The maximum adsorption capacity of the adsorbent was obtained 344.83 mg/g at C0 = 210 mg/L, T = 328 K, and pH = 5. The experimental kinetic and equilibrium data were well adjusted with pseudo-second-order kinetic models and Langmuir and Temkin isotherm models, respectively, according to linear regression (R2), chi-square statistic (χ2), and the sum of the squares of the errors (SSE). The thermodynamics parameters were analyzed and the results showed an endothermic and spontaneous adsorption process. Regeneration and reuse results of the synthesized biocomposite represented highly adsorption efficiency after five adsorption cycle stages.

Novel hollow beads of carboxymethyl cellulose/ZSM-5/ZIF-8 for dye removal from aqueous solution in batch and continuous fixed bed systems.

Zeolitic imidazolate frameworks are a class of metal-organic frameworks that are topologically isomorphic with zeolites. In this study, bionanocomposites of carboxymethyl cellulose-based ZSM-5/zeolitic imidazolate framework (CMC/ZSM-5/ZIF-8) hollow beads with different compositions were synthesized and employed as an adsorbent for methylene blue removal from aqueous solution in batch and continuous fixed bed systems. FESEM, FTIR, XRD, and BET measurements have been employed for characterizing the synthetic bionanocomposites. The effect of time and concentration on adsorption processes, regeneration, and reuse investigations were performed. The equilibrium batch adsorption capacities for CMC, CMC/ZIF-8, CMC/ZSM-5, and CMC/ZSM-5/ZIF-8 adsorbents were 12.01, 13.06, 11.53, and 10.49 mg/g, respectively. The batch adsorption was investigated using pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich kinetic models and the results showed that all four adsorbents are consistent with all models but the pseudo-first-order model showed more consistency. The equilibrium continuous adsorption capacities for CMC, CMC/ZIF-8, CMC/ZSM-5, and CMC/ZSM-5/ZIF-8 adsorbents were 10.56, 11.87, 9.29, and 8.15 mg/g, respectively. The continuous adsorption was investigated by Thomas, Adam-Bohart, Yoon-Nelson, Wolborska, and Modified Dose Response kinetic models and the results showed that the adsorbents showed more consistency with models of Thomas, Yoon-Nelson, and Modified Dose Response. Besides, the generation process was successfully assessed in five steps.

Synthesis of a chitosan/polyvinyl alcohol/activate carbon biocomposite for removal of hexavalent chromium from aqueous solution.

In this study, a biocomposite of chitosan/poly vinyl alcohol/activated carbon was synthesized and used for hexavalent chrome removal from aqueous solution. The synthesized adsorbent was characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) analysis. The effect of important variables such as pH, concentration, contact time, temperature, and adsorbent dosage was investigated. The value of pHPZC for the adsorbent was evaluated at 4.9. Results showed that adsorption of chrome onto the adsorbent follows the Langmuir isotherm model and has a pseudo-second-order kinetic model. The maximum capacity of chrome adsorption was determined 109.89 (mg/g) according to the Langmuir isotherm model. According to adsorption results, the removal percentage of chrome increases with increasing the activated carbon content in the biocomposite, the adsorbent dosage, and decreasing the initial chrome concentration, pH, and temperature. The results showed that the synthesized adsorbent can be used as an effective adsorbent for chrome removal from aqueous solutions.

Preparation and performance of alginate/basil seed mucilage biocomposite for removal of eriochrome black T dye from aqueous solution.

Mucilage extracted from Basil seeds were captured in calcium alginate biobeads. The beads were tested as eco-friendly adsorbents to eriochrome black T dye from aqueous solution. The synthesized biocomposite was characterized by FESEM, EDX, TGA, and FTIR techniques. Batch and continuous experiments were performed for dye adsorption studies using the synthesized biocomposite. The effect of contact time, pH, initial concentration of dye, and amount of adsorbent on dye adsorption capacity, and also kinetics, isotherm, thermodynamics, regeneration, and swelling investigations were performed. The results showed that the adsorption of eriochrome black T follows the pseudo-second-order batch kinetic model, Yoon-Nelson and Thomas dynamic models, and Freundlich isotherm model. The thermodynamic results showed that the dye adsorption process with the synthetic adsorbent is an exothermic spontaneous process.

Fabrication of TiO2/Zn2TiO4/Ag nanocomposite for synergic effects of UV radiation protection and antibacterial activity in sunscreen.

A systematic and detailed study has been designed and conducted, taking into account some of the proposed benefits such as increased efficiency, transparency, unique texture, protection of active ingredient and higher consumer compliance of cosmetics containing nano-sized metal oxides. The objective of the present study was to develop novel sunscreen cream containing a TiO2/Zn2TiO4/Ag nanocomposite for enhanced UV radiation protection and antibacterial activity. In this study, TiO2/Zn2TiO4/Ag nanocomposite was prepared using sol-gel method and characterized by FESEM, EDX, XRD, TGA, UV-vis spectrophotometry, and FTIR techniques. Different sunscreen creams were formulated by incorporating the nanocomposite and TiO2 nanoparticles and the Sun Protection Factor (SPF) against ultraviolet radiation and antibacterial activity were examined. The antibacterial activity of synthesized TiO2/Zn2TiO4/Ag nanocomposite was investigated against gram positive (S. aureus) and gram negative (Escherichia coli). TiO2/Zn2TiO4/Ag nanocomposite has a higher protective factor compared to TiO2 nanoparticles. The results show that the average particle sizes of the synthesized nanoparticles are on a scale below 100 nm. The energy gap of the TiO2/Zn2TiO4/Ag nanocomposite was 3.01 eV which is close to the energy gap of the pure TiO2 nanoparticles. The nanocomposite presents higher UV absorption than the pure TiO2 nanoparticles. According to MIC test, minimum inhibitory concentration for this nanocomposite was 10 mg/ml. According to the MTT test, up to 0.3 µg/ml of this nanocomposite was found not to be susceptible to toxicity and almost 79.5 % of the cells exposed to nanoparticles had vital activities. In fact, TiO2/Zn2TiO4/Ag nanocomposite addition to cream was considered, not only to achieve the best protection over the whole UV range but also to take advantage of any synergistic effects of them in sunscreens.

Alginate beads impregnated with magnetic Chitosan@Zeolite nanocomposite for cationic methylene blue dye removal from aqueous solution.

In this study, magnetic bionanocomposite of sodium alginate (an anionic polysaccharide), chitosan (a cationic polysaccharide), impregnated with natural zeolite, and cross-linked with glutaraldehyde and CaCl2 in order to improve the stability, are prepared and used to methylene blue removal from aqueous solution. The synthesized magnetic Zeolite/Chitosan/Alginate (MZ/CS/AL) bionanocomposite was analyzed and characterized by FeSEM, EDX, XRD, BET surface area analysis, VSM, TGA, and FTIR techniques. The efficiency of the MZ/CS/AL biosorbent was studied by measuring the uptake using the batch and continuous technique experiments. The effect of contact time, pH, initial concentration of dye, and amount of adsorbent on dye adsorption capacity, kinetics, isotherm, thermodynamics, regeneration, and swelling were investigated. The results showed that the adsorption of methylene blue follows the pseudo-second-order kinetic model and Freundlich isotherm model. The thermodynamic results showed that dye adsorption process with synthetic adsorbent is an exothermic spontaneous process.

Dye removal from aqueous solution by a novel dual cross-linked biocomposite obtained from mucilage of Plantago Psyllium and eggshell membrane.

In this study, a novel dual cross-linked biocomposite of Plantago Psyllium mucilage, eggshell membrane, and alginate was prepared and used for removal of cationic methylene blue and anionic methyl orange dyes from aqueous solution. The fabricated biocomposite was characterized by FeSEM, EDX, XRD, TGA, BET, and FTIR analyses. Parameters such as kinetics, isotherm, thermodynamics, regeneration, swelling, and the influence of contact time, dye concentration, adsorbent amount, and pH on the dye adsorption capacity were determined. The maximum adsorption capacities of biocomposite were obtained for 0.05 g of the adsorbent with an initial concentration of 10 ppm in pH equal to 11 and 3, about 5.45 and 3.25 mg/g for methylene blue and anionic methyl orange, respectively. The thermodynamic results showed that the adsorption of the dye processes are a spontaneous exothermic process. The results showed that the adsorption of the dyes follows the pseudo-second-order kinetic model and the isotherm of both the dyes fit the Freundlich model. The experimental breakthrough curves were analyzed using different dynamic models of Bohart-Adams, Thomas, and Yoon-Nelson. The continuous adsorption process of dyes by the synthesized adsorbent was shown an appropriate consistency with the dynamic models, and best fitted to the Thomas and Yoon-Nelson models.

Synthesis of zeolite/nickel ferrite/sodium alginate bionanocomposite via a co-precipitation technique for efficient removal of water-soluble methylene blue dye.

In this study, we sought to synthesize magnetic nanocomposite of zeolite/nickel ferrite through co-precipitation method and modify its surface by sodium alginate to enhance its methylene blue adsorption capacity and to prevent its oxidation. Nanocomposite characteristics were investigated by SEM, VSM, XRD and FTIR analyses. The results indicate that nanocomposite synthesis and modification has been completely successful. Adsorption thermodynamics, kinetics, and isotherms were examined and parameters were optimized by Minitab software using experimental design method, response surface methodology and Box-Behnken design. The highest capacity of methylene blue adsorption from the aqueous solution obtained at optimal pH of 5, the initial dye concentration of 10 mg/L and an adsorbent amount of 0.03 g was about 54.05 mg/g. Analyzing kinetic data of adsorption experiments confirmed that adsorption process complies with the pseudo-second-order kinetic model. Assessing equilibrium isotherm data at different temperatures showed that these data are in good agreement with Langmuir isotherm model.

Methylene Blue removal from aqueous solution by a biocomposite synthesized from sodium alginate and wastes of oil extraction from almond peanut.

In this study, the removal of Methylene Blue dye was investigated by biocomposite beads synthesized from sodium alginate and wastes of oil extraction from almond peanut. Prepared biocomposite was characterized using X-ray diffraction, Infrared spectroscopy, scanning electron microscopy, Energy Dispersive X-Ray analysis. The adsorption capacities of Methylene Blue were investigated with respect to the effect of the adsorbent amount, pH value, and initial dye concentration. The kinetic adsorption data were analyzed by the pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion kinetic models. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The pseudo-second-order kinetic and Freundlich isotherm equations were found to describe the adsorption mechanism. The thermodynamic studies showed that the adsorption process is a spontaneous and exothermic process with increased entropy. The removal percentage and maximum adsorption capacity of Methylene Blue by biocomposite were equal to 90% and 22.8mg/g, respectively. The high registered capacities of Methylene Blue removal suggest the potential use of the biocomposite in the treatment of contaminated wastewaters.

Mechanisms of heavy metal removal using microorganisms as biosorbent.

Release and distribution of heavy metals through industrial wastewaters has adverse affects on the environment via contamination of surface- and ground-water resources. Biosorption of heavy metals from aqueous solutions has been proved to be very promising, offering significant advantages such as low cost, availability, profitability, ease of operation, and high efficiency, especially when dealing with low concentrations. Residual biomasses of industrial microorganisms including bacteria, algae, fungi, and yeast have been found to be capable of efficiently accumulating heavy metals as biosorbent. This paper presents and investigates major mechanisms of biosorption and most of the functional groups involved. The biosorption process includes the following mechanisms: transport across cell membrane, complexation, ion exchange, precipitation, and physical adsorption. In order to understand how metals bind to the biomass, it is essential to identify the functional groups responsible for metal binding. Most of these groups have been characterized on the cell walls. The biosorbent contains a variety of functional sites including carboxyl, imidazole, sulfydryl, amino, phosphate, sulfate, thioether, phenol, carbonyl, amide, and hydroxyl moieties that are responsible for metal adsorption. These could be helpful to improve biosorbents through modification of surface reactive sites via surface grafting and/or exchange of functional groups.