Bio-based Adsorbent Research Articles

Adsorption of rare earth elements using bio-based sorbents

Rare earth elements (REEs) have recently received significant attention due to their irreplaceable industrial application for the number of crucial advanced technologies in production of permanent magnets, batteries, luminescence lamps, lasers and other electronic and electrical goods. These technologies have been strongly affecting present consumption of REEs as well as looking for alternative sources, that would guarantee their sufficient supply for the future demand. This study investigates one of the possible and widely employed techniques for the efficient and at the same time, environmentally friendly recovery of REEs by adsorption using bio-based adsorbents. Overall, three bio-sorbents with different composition (residual biomass originated from agriculture and bio-refineries) were examined to study removal efficiency of the 7 most commonly used REEs in mixed aqueous solution. Batch adsorption experiments were carried out at the room temperature, varying the pH value (pH=1,54; 4,24) and different initial concentration of REEs to determine optimum condition for their recovery. Results revealed that removal efficiency for most of the REEs was much higher at pH=4,24 and reached 70-100% for the minimal concentrations and 30-40 % at maximal initial concentrations respectively. Adsorbent containing residual biomass and chitosan showed to be the most effective bio-sorbent for recovery of most of the REEs. In order to describe and fit the obtained data Langmuir and Freundlich isotherms models were employed.

Nanocellulose as a novel nanostructured adsorbent for environmental remediation: a review

Nanocellulose is a lightweight material with strong mechanical strength, inexpensive production costs and safe handling compared to synthetic nanoparticles. Thanks to the high specific surface area, broad possibility of surface modification and high mechanical strength, nanocellulose has emerged as a new class of biobased adsorbent with promising potential application in environmental remediation. Many classes of pollutants could be adsorbed by nanocellulose, including heavy metals, dissolved organic pollutants, dyes, oil and undesired effluents. The possibility for the regeneration of the nanocellulose adsorbent is another benefit driving attempts to fully exploit this new class of nanostructured biobased material. In this review, an update of the most relevant uses of nanocellulose as a new class of adsorbents for environmental remediation is outlined. An emphasis on the key advancement of surface modifications of nanocellulose to enhance the adsorption efficiency according to the pollutant class is highlighted.

Application of cellulose nanofibers to remove water-based flexographic inks from wastewaters.

Water-based or flexographic inks in paper and plastic industries are more environmentally favourable than organic solvent-based inks. However, their use also creates new challenges because they remain dissolved in water and alter the recycling process. Conventional deinking technologies such as flotation processes do not effectively remove them. Adsorption, coagulation/flocculation, biological and membrane processes are either expensive or have negative health impacts, making the development of alternative methods necessary. Cellulose nanofibers (CNF) are biodegradable, and their structural and mechanical properties are useful for wastewater treatment. TEMPO-oxidised CNF have been evaluated for the decolourisation of wastewaters that contained copper phthalocyanine blue, carbon black and diarlyide yellow pigments. CNF in combination with a cationic polyacrylamide (cPAM) has also been tested. Jar-test methodology was used to evaluate the efficiency of the different treatments and cationic/anionic demand, turbidity and ink concentration in waters were measured. Results show that dual-component system for ink removal has a high potential as an alternative bio-based adsorbent for the removal of water-based inks. In addition, experiments varying CNF and cPAM concentrations were performed to optimise the ink-removal process. Ink concentration reductions of 100%, 87.5% and 83.3% were achieved for copper phthalocyanine blue, carbon black and diarlyide yellow pigments, respectively. Flocculation studies carried out show the decolourisation mechanism during the dual-component treatment of wastewaters containing water-based inks.

Development of a green and sustainable clean up system from grape pomace for heavy metal remediation

Bio-based adsorbents from grape pomace used in waste water clean-up activities are demonstrated in the present study. An application of thermal treatment to the oven dried and grinded grape pomace resulted in the development of a porous carbonaceous biosorbent having selective surface sites favourable for binding of metal ion adsorbates. While the electrostatic nature of adsorbent-adsorbate interactions were indicative from pH and FTIR studies, “Weber and Moris” plots helped to estimate the nature of the adsorbate transfer process which is interplay of film and particle diffusion. The maximum adsorption capacity was determined from Langmuir plot and reveals the higher uptake of Pb2+ in comparison to Cd2+. The relationship of the divalent cationic properties of the selected adsorbates in aqueous media is reflected. Effect of various operating parameters along with equilibrium, kinetic and thermodynamic studies reveal the efficacy of the GPMAC with an adsorption capacity comparable to other reported adsorbents. The developed adsorbent was tested under a real metal fabricating industrial effluent where despite the presence of competing pollutants and a high COD, greater than 89% metal removals was achieved. Also high regeneration capacity of GPMAC for reuse has established the practicality of the developed system. The experimental results reveal that the winery wastes have the potential for cost effective and eco-friendly wastewater treatment. Also, developing an effective, low cost adsorbent from winery solid waste like grape pomace is a new promising strategy and sustainable solution towards its efficient waste valorisation.

Impregnation of Chitosan onto Activated Carbon for Adsorption Selectivity Towards CO2: Biohydrogen Purification

In this study, a novel bio-based adsorbent was developed for biohydrogen purification by an adsorption process. Palm shell activated carbons were immersed in the chitosan solutions at the concentrations between 0.1-2 g/L.The results showed that the impregnation of chitosan onto activated carbons at every concentration under the investigation changed the BET surface areas, pore size distribution, CO 2 adsorption capacity and the CO 2 /H 2 selectivity. The chitosan impregnated activated carbon that was the most suitable for carbon dioxide/hydrogen separation was the one impregnated in the 0.1 g/L chitosan solution yielding 0.12 g chitosan per 100 gram activated carbon. The modified activated carbon was found to have 11% higher CO 2 adsorption capacity than the native activated carbon even though its BET surface area was reduced by 3% due to the impregnation process. From a lab-scale pressure swing adsorption process using the modified activated carbon as the adsorbent (under an adsorption pressure of 4 bar and the feed flow rate of 2 L/min 50-30-20 mixture of CO 2 , H 2 and N 2 for a period of 2 min per cycle), the CO 2 concentration in the effluent was not detected for at least 5 cycles.

Magnetic polydopamine decorated with Mg–Al LDH nanoflakes as a novel bio-based adsorbent for simultaneous removal of potentially toxic metals and anionic dyes

A novel MPL bifunctional material fabricated by an easy and green approach was applied for the simultaneous removal of potentially toxic metals and anionic dyes.

Physicochemical study of a bio-based adsorbent made from grape marc

In the last few years bio-oxidized grape marc (formulated by encapsulation in calcium alginate beads) has been proposed as an eco-friendly adsorbent for wastewater treatment. However, the physicochemical properties of the bioadsorbent have not yet been reported. This study analyzed the stability of the bio-based adsorbent before and after adsorption of dye compounds from winery wastewater. Minor morphological changes in the adsorbent were observed after it was used to treat the wastewater. The physicochemical properties of the bioadsorbent at equilibrium were also evaluated. The process of adsorption onto the heterogeneous surface of the bio-based adsorbent was best described by the Freundlich isotherm, and the adsorption process was physically controlled (E=0.61kJ/mol).

Heterogenous Lignocellulosic Composites as Bio-Based Adsorbents for Wastewater Dye Removal: a Kinetic Comparison

Different lignocellulosic substrates consisting of modified barley husk, peanut shells and sawdust were entrapped in calcium alginate beads and used as adsorbents to remove dye compounds from vinasses. For comparative purposes, a biocomposite formulated with humus was also included in this work. Kinetic studies were carried out by applying pseudo-first-order, pseudo-second-order, Chien–Clayton and intraparticle diffusion models, observing a good agreement between theoretical and experimental results when the data were adjusted to pseudo-second-order kinetic model. The results of this study show that lignocellulosic-based biocomposites could be used as an effective and low-cost adsorbent for the removal of dyes from aqueous solutions. Among the heterogeneous biopolymers evaluated, the biocomposite based on barley husk gave the best capacity for dye removal. Moreover, in all cases, it was found that there exists a direct relationship between the capacity of the biocomposites to remove dyes and the percentage of carbon contained in the lignocellulosic residues.

Experimental Study on The Adsorption of Malachite Green in Simulated and Real Effluent by Bio-Based Adsorbents

The purpose of this study is to investigate the potential use of biomass-based adsorbents, such as sugarcane bagasse, sawdust, and neem leaf, for the removal of malachite green from simulated and real effluent. The adsorbents prepared from bagasse are pretreated with formaldehyde, sulfuric acid, and phosphoric acid to improve the surface properties like porosity and surface area and its reflection on adsorption capacity. Neem leaf was used as an untreated adsorbent to compare the performance with that of treated adsorbents. The adsorption capacity of treated bagasse, sawdust, and untreated neem leaf adsorbent were compared with that of commercial powdered–activated carbon. The effect of initial dye concentration, adsorbent dosage and adsorbent surface modification on dye removal was examined for different contact time. It was observed that the adsorption efficiency of phosphoric acid–treated bagasse and neem leaf powder gives higher percentage of dye removal (97%) as compared to sulfuric acid- and formaldehyde-treated adsorbents (89% and 86%). Experiments performed on a real effluent using PSB as the adsorbent indicated a maximum color removal of 79% for an adsorbent dosage of 1 g/100 mL. Also equilibrium studies of the adsorption process were carried out and the adsorption data were fitted to Langmuir and Freundlich isotherm models.

Adsorptive Properties of Biobased Adsorbents

Water and methanol vapor adsorption isotherms for native and modified potato starch were investigated. For obtaining the best fit for the experimental data several models based on the BET approach was evaluated. The hypothesis that water is adsorbed on the starch granules at the primary and secondary adsorption sites as well as a concept considering the adsorbent fractality were also tested. It was found, that the equilibrium adsorption points in the examined range of relative humidity (0.03–0.90) were most accurately predicted by using a three-parameter model, proposed by Kats and Kutarov (1998). For methanol a good representation of experimental data was obtained using model proposed by Talu and Meunier (1996).

Separation of Ethanol–Water Mixtures Using Molecular Sieves and Biobased Adsorbents

The potential use of new biobased adsorbents and different types of molecular sieve was assessed in the separation of the ethanol–water azeotrope. Molecular sieves of type 3A, type 4A, and type 5A and biobased adsorbents such as natural corncobs, natural and activated palm stone and oak, were used in this study. Each of these adsorbents was packed in a column, which was surrounded by a heating jacket. The jacket temperature was maintained constant in an attempt to maintain the packed-column at constant temperature. The water concentration in the feed solution was varied from 5% to 12% (weight basis). Although the initial concentration of ethanol in the flask was constant at the beginning of the experiment, it varied with time due to boiling. The breakthrough curves of water sorption on these adsorbents at different water contents showed that among the molecular sieves examined, type 3A molecular sieves gave the best separation of the ethanol–water system and among biobased adsorbents examined, natural palm stone was the best. The Guggenheim, Anderson, and De Boer (GAB) model at different water contents represented the isotherms for water sorption on molecular sieves and biobased adsorbents. In addition, the surface area of adsorbents and maximum water uptake were calculated. Type 3A molecular sieves were determined to have the largest surface area and the highest value of water uptake compared with the other two types of molecular sieve. However, for the biobased adsorbents, activated palm stone was found to have the largest surface area and the highest value of water uptake compared to the other biobased adsorbents. It was found that upon activation, the adsorption capacity of biobased adsorbents was not enhanced. On the contrary, the activation gave negative results on some occasions.

Adsorptive Distillation Using Molecular Sieves and Low-Cost Biobased Adsorbents for the Break-up of the Isopropanol–Water Azeotrope

The separation of isopropanol from aqueous vapours near the azeotropic composition was investigated using fixed beds packed with type A molecular sieves and biobased adsorbents. Natural palm stones, oak and corncobs were used as new biobased adsorbents. It was possible to break the azeotrope up using any of the afore-mentioned adsorbents. However, in terms of the breakthrough time and the purity of isopropanol in the condensate, the 3 Å molecular sieve was the best followed by 4 Å, palm stones, natural corncobs, natural oak and 5 Å molecular sieves. Activated carbons prepared from the biobased adsorbents showed a lower performance than their natural precursors.

Biobased adsorbents for drying of gases

Fundamental, structural and compositional studies on the properties of corn grits and their ability to selectively adsorb water from organic vapors have resulted in new bio-based adsorbents. Structure/function relationships of these bio-based adsorbents are reviewed.