Spent Adsorbent Research Articles

Effects of Soils on Environmental Stability of Spent Mg-Based and Ca-Based Adsorbents Containing Arsenite

Spent adsorbents used in As removal treatment may re-leach As. In this study, the effects of soil on spent Mg-based and Ca-based adsorbents were investigated. The spent adsorbents containing arsenite (As(III)) were prepared by adsorbing As(III) on MgO, Mg(OH)2, CaO, and Ca(OH)2 powder reagents. Kuroboku soil (Ku), yellow-brown forest soil (YF), Kanuma soil (Ka), river sand (RS), and mountain sand (MS) were used as soil samples. The As leaching ratio was examined in coexistence with soil via shaking tests, and the results were compared with those of a previous study on adsorbents containing arsenate (As(V)). The environmental stability of the spent adsorbents was found to vary greatly depending on the combination of the As valence, adsorbent type, and soil type. However, regardless of the adsorbent or soil type, the spent adsorbents containing As(III) were more likely to leach As than those containing As(V). Additionally, the As leaching ratio was generally lower in Ku and YF and higher in Ka, RS, and MS. For environmentally friendly and sustainable As removal treatment, disposal, and management, the selection of MgO as the adsorbent and treatment involving the oxidation treatment of As(III) to As(V) before adsorbing As onto adsorbents are recommended.

Repurposing Co-Fe LDH and Co-Fe LDH/Cellulose micro-adsorbents for sustainable energy generation in direct methanol fuel cells

Spent adsorbents need to be recycled as well as valorized to obtain long-term benefits from the adsorption of contaminants from wastewater. Co-Fe LDH and Co-Fe LDH/cellulose-layered double hydroxide (LDH) were prepared for crystal violet (CV) adsorption. FT-IR, XRD, SEM, TEM, and, zeta potential analyses confirmed the micro-composites. The parameters examined in this study were the initial pH, initial concentration, adsorbent dose, contact time, adsorption isotherm, and adsorption kinetics. The removal percent was 97.5 % and 88 % for Co-Fe LDH and Co-Fe LDH/cellulose, respectively. A maximum adsorption capacity was 69.4 and 50.0 mg g−1 for Co-Fe LDH and Co-Fe LDH/cellulose, respectively, at pH = 9. The Langmuir-Freundlich model can adequately explain the isotherm processes of LDH and LDH/cellulose; R2 was 0.96 and 0.95, respectively. The spent adsorbents (Co-Fe LDH/CV and Co-Fe LDH/Cellulose/CV) were applied once again as catalysts for electro-oxidation in direct-methanol fuel cells. Due to its high stability in the basic medium (NaOH), the waste material was exploited as an active catalyst to support methanol oxidation. It displayed a better efficiency of 74.75 % and a current density of 76 mA/cm2 at 50 mV/s in 1 M methanol for Co-Fe LDH/CV. The suggested technique opens up a completely new channel for reusing waste into high-value materials for application in electrocatalytic energy generation.

Neolamarckia cadamba (cadamba) waste pulp as a natural and techno-economic scavenger for methylene blue from aqueous solutions

In this work, Neolamarckia cadamba (cadamba), also known as bur flower tree has been exercised to demonstrate as an excellent methylene blue scavenger from simulated as well as industrial wastewater. The particle morphology and structural insights were gained from FESEM, BET surface area, FTIR, and pHZPC. The adsorption behavior was mapped by different physico-chemical parameters such as contact time, pH, input concentration, and temperature. Experimental data reveal rapid adsorption, and >90% uptake was successful within the first 15 min and reaches equilibrium by 45 min (removal efficiency = 94.15%) at neutral pH. The maximum adsorption capacity was found to be 115.60 mg/g. The uptake process follows pseudo-second-order kinetics (R2 = 0.99), confirming a chemisorption process while the Langmuir model (R2 = 0.99) satisfactorily addresses the adsorption path. Thermodynamic parameters suggest a spontaneous, feasible, and exothermic process with increased entropy. Spent adsorbent could easily be regenerated in up to 74% using 1:1 MeOH/H2O with a potential of three-cycle use. Real-time efficacy has been established with an MB containing industrial effluent and up to 44.70% adsorption, which confirms the material’s practical applicability. Statistical reliability was confirmed by the relative standard deviation. Altogether, the present material offers clean and green removal of methylene blue dye from versatile wastewater.

The influence of cross-linking density on the efficiency of post-synthetic sulfonation of hyper-cross-linked polymers and their adsorption capacity for antibiotic pollutants

Hyper-cross-linked polymers (HCPs) attract increasing attention as promising adsorbents for removal of organic pollutants from water. The present work reveals for the first time that the efficiency of the post-synthetic sulfonation of HCPs-based adsorbents and their reactivity in removal of selected polar antibiotic pollutants can be simply controlled by adjusting the cross-linking density of the polymer network. The study included both the evaluation of the mechanism and kinetics of the adsorption process over sulfonated HCPs, as well as the determination of their stability, recyclability, and affinity toward various antibiotics. The latter was established based on adsorption tests using mono- and multicomponent mixtures of different structure antibiotics (ciprofloxacin, tetracycline, sulfamethoxazole and amoxicillin). The adsorption capacity of all sulfonated polymers was found to be directly proportional to the concentration of -SO3H functions and inversely proportional to the cross-linking density of the parent HCPs. The most promising sulfonated polymer had approximately 4 times higher adsorption capacity toward ciprofloxacin than commercial carbon-based adsorbent Norit (427.5 vs. 110.5 mg/g, respectively). The main adsorption mechanism over sulfonated HCPs was chemisorption of the antibiotics via ionic interactions with surface -SO3H groups. Spent adsorbent could be successfully recycled ten times without any loss in its efficiency.

The reuse potential of spent ZIF-8@GO-COOH nano adsorption materials: Study on their impact on the hydration mechanism and mechanical properties of cement-based composites

Spent adsorbents often contain harmful substances, which may have an impact on the ecological environment if these substances enter the environment. This study mainly introduces a safe treatment method for solid waste formed after heavy metal ions are adsorbed by an efficient adsorbent, ZIF-8@GO-COOH. This work mainly discusses the impact of solidifying the spent adsorbent in the cement system on the cement mechanical properties and hydration process. The experimental results showed that when the dosage of the spent adsorbent was 0.01%, 0.02%, 0.03%, and 0.04%, respectively, the compressive strength of 28 d was increased by 4.24%, 6.16%, 7.19%, and 8.87%, respectively, compared with the cement without spent adsorbent. Introducing spent ZIF-8@GO-COOH in the cement production process does not have a negative impact on the cement mechanical properties, and can refine the cement pore structure and dense microstructure, thereby improving the compressive strength. The Toxicity Characteristic Leaching Procedure (TCLP) results showed that solidifying the spent adsorbent with cement can effectively reduce the leaching of heavy metal ions in the spent adsorbent. This study solidifies the spent ZIF-8@GO-COOH nanoadsorbent material into the cement system as a sustainable alternative to landfilling. This treatment method has certain economic benefits and safety, and has some reference significance for promoting the development and improvement of spent adsorbents and improving their safe treatment and reuse.

Stem powder and its active carbon of Arachis hypogaea plant for lead (II) removal: application to treat battery-based industrial effluents

Stem powder and its active carbon of Arachis hypogaea plant are identified to have strong adsorptivity for lead ions. The bio-sorbents are characterized by conventional methods including XRD and FTIR analysis. These biomaterials are investigated for their maximum adsorption for lead ions by optimizing the extraction conditions. The maximum removal is observed in the pH range of 6–7 for both sorbents. With stem powders, the removal is 76.0% from a simulated lead solution of concentration: 20.0 mg/L with 1.5 g/L of the sorbent and at an equilibration time of 2.0 h. With the active carbon, the maximum extraction of: 86.0% is observed at pH: 6.5 with 1.0 g/L of the sorbent after an equilibration time of 1.5 h. The sorption capacities are 32.0 mg/g for stem powders, and 40.5 mg/g for active carbon. Many co-ions have marginal interference. Spent adsorbents can be recycled after regeneration. Thermodynamic investigations reveal the spontaneity and endothermic nature of adsorption. High ΔH values viz., 26.45 kJ/mole for AHSP and 46.40 kJ/mole for AHSAC, confirm the bonding of Pb2+ ions with the sorbents is either “ion-exchange” and/or a sort of “complex formation.” The disorder at the solid and liquid boundary is indicated by high positive ΔS values and it is a favorable condition for good Pb2+ adsorption. On analysis of different kinetic and isotherm models, the sorption of Pb2+ ions follows Pseudo-2nd order and Langmuir models. This confirms the mono-layer adsorption of Pb2+ ions on the humongous surface of the sorbent. The adsorbents are successfully applied to treat industrial effluent samples.

Selective Capture of Pd(Ii) from Aqueous Media by Ion-Imprinted Dendritic Mesoporous Silica Nanoparticles and Re-Utilization of the Spent Adsorbent for Suzuki Reaction in Water

Selective Capture of Pd(Ii) from Aqueous Media by Ion-Imprinted Dendritic Mesoporous Silica Nanoparticles and Re-Utilization of the Spent Adsorbent for Suzuki Reaction in Water

Recycling spent water treatment adsorbents for efficient electrocatalytic water oxidation reaction

Heavy metal contaminated spent adsorbents are of great environmental concern due to their hazardous effects and large-scale accumulation in the natural environment. Converting massive spent adsorbents into efficient electrocatalysts with a facile strategy can address the challenge of growing energy demand and achieving carbon neutral goal. Herein, we demonstrated a "spent adsorbents to heterostructured electrocatalysts" conversion strategy based on the "waste-to-wealth" principle. Via a facile boriding process, the metal ions laden biochar-based spent adsorbents (SA) have been totally transformed into magnetic metal borides/biochar heterostructures, which exhibit excellent activities towards oxygen evolution reaction. The optimized NiCuFeB/SA catalyst takes a low overpotential of 251 mV to drive a current density of 10 mA cm−2, outperforming many Ni/Fe-based catalysts synthesized from commercial material resources. Comprehensive analyses suggest the high catalytic efficiency mainly attributes to the porous biochar confined well-dispersed nano-sized metallic borides, the in-situ evolved active metal (oxy)hydroxides, favourable charge-transfer kinetics, as well as the heterostructure and amorphous feature. This work offers a general strategy to efficiently reutilize the spent metal-bearing biochar-based adsorbents, which can be extended to advanced energy applications-oriented reutilization of other metal-contaminated solid wastes in an economically and environmental-benign manner.

Iron-alginate beads doped with green synthesised ‘nano-CeO2-ZrO2’ as an effective adsorbent for removal of highly toxic Arsenic-ions from polluted water

ABSTRACT Nano-mixed oxides of ‘CeO2-ZrO2ʹare synthesised through green methods. Sapindus plant seeds skins extract functions as an effective stabilising agent in controlling the size of the nano particles of ‘CeO2-ZrO2ʹ. These mixed oxide nano-particles are embedded in ‘Iron alginate (nCeO2-ZrO2-Fe-alig). The beads are investigated as adsorbent for As (III/V) removal. Extraction conditions are investigated and optimised. Adsorption capacities of the beads are as high as:153.25/140.5 mg/g for As (III)/As (V). Sorption nature is analysed adopting FESEM, EDX, XRD and FTIR investigations. Adsorption mechanism is investigated by various isotherm models. Endothermic nature and spontaneity of sorption process are revealed by thermodynamic studies.Pseudo-second-order model defines adsorption kinetics. Spent adsorbent can be reused. Method developed is applied to treat arsenic-polluted ground water in West Bengal, India.

Synthesis of nanoZrO2 via simple new green routes and its effective application as adsorbent in phosphate remediation of water with or without immobilization in Al-alginate beads.

Nano particles of ZrO2 of average size 10.91 nm are successfully synthesized via green routes from a solvent blend of water and ethylene glycol (4:1 v/v). Bio-extract of seeds of Sapindus plant is employed as stabilizing and/or capping agent and homogeneous method of precipitation is adopted to generate the precipitating agent. The nZrO2 particles are immobilized in aluminum alginate beads (nZrO2-Al- alig). Nano-ZrO2 and beads are investigated as adsorbents for the extraction of phosphate from water. The controlling physicochemical parameters are studied for the maximum phosphate removal using simulate water. The optimum conditions are: pH: 7; sorbent dosage: 0.1 g/100 mL for nZrO2 and 0.08 g/100 mL for beads; equilibration time: 30 min.for nZrO2 and 35 min for beads; initial phosphate concentration: 50 mg/L; temperature: 30 ± 1 °C; 300 rpm. The adsorption capacities are: 126.2 mg/g for nZrO2 and 173.0 mg/g for 'nZrO2-Al- alig' and they are higher than many reported in literature. The beads, besides facilitating the easy filtration, are exhibiting enhanced cumulative phosphate-adsorption nature of nanoZrO2 and Al-alginate. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) investigations are employed in characterizing the adsorbents. Of the various isotherm models analyzed to assess the nature of adsorption, Freundlich model provides the best correlation (R2 = 0.99 for nZrO2 and R2 = 0.99 for 'nZrO2-Al-alig'), indicating the heterogeneous and multi-layered adsorption process. Thermodynamic studies reveal the endothermic and spontaneous nature of sorption. Pseudo-second-order model of kinetics describes the adsorption well. Spent adsorbents can be regenerated with marginal loss of adsorption capacity until five cycles. The sorbents are successfully applied to remove phosphate from polluted lake water samples.

Extraction of active pharmaceutical ingredients from simulated spent activated carbonaceous adsorbents

Activated carbon (AC) and activated biochar (ABC) are widely used as sorbents for micropollutant removal during water and wastewater treatment. Spent adsorbents can be treated in several ways, e.g., by incineration, disposal in landfills, or reactivation. Regeneration is an attractive and potentially more economically viable alternative to modern post-treatment practices. Current strategies for assessing the performance of regeneration techniques often involve only repeated adsorption and regeneration cycles, and rarely involve direct measurements of micropollutants remaining on the adsorbent after regeneration. However, the use of regenerated adsorbents containing such residual micropollutants could present an environmental risk. In this study, the extraction of eight active pharmaceutical ingredients (APIs) commonly found in treated effluents was evaluated using 10 solvents and sorption onto three different carbon materials. An optimized extraction method was developed involving ultrasonication in 1:1 methanol:dichloromethane with 5% formic acid. This method achieved recoveries of 60 to 99% per API for an API concentration of 2 μg/g char and 27 to 129% per API for an API concentration of 1 mg/g char. Experiments using a mixture of 82 common APIs revealed that the optimized protocol achieved extraction recoveries above 70% for 29 of these APIs. These results show that the new extraction method could be a useful tool for assessing the regenerative properties of different carbon sorbents.

Adsorptive Removal of Copper Ions from Polluted Water Using Sorbents Derived from Cordia dichotoma, Albizia thompsonii and Polyalthia cerasoides Plants

Three different activated carbons as effective adsorbents were prepared by digesting the stems of Cordia dichotoma, Albizia thompsonii and Polyalthia cerasoides plants in conc. H2SO4 for Cu2+ removal from wastewater. The sorption natures of these sorbents are optimized with respect to various physico-chemical characteristics for the maximum Cu2+ removal using simulated waters. Cordia dichotoma (CDAC), Albizia thompsonii (ATAC) and Polyalthia cerasoides (PCAC) activated carbons show good sorption capacities of values: 97.0, 76.8 and 66.7 mg/g, respectively in a wide pH ranges. Unlike that of other two activated carbons, Cordia dichotoma activated carbon is effective even in acid conditions, indicting its direct applicability to Cu-based industrial effluents which are generally acidic in nature. Interference of two fold excess of co-ions is minimal. The established extraction conditions for the removal of more than 95.0% from 10 ppm Cu2+ solution at room temperature (303 K) using CDAC as sorbent are: pH: 3-9; time of equilibration: 1 h; sorbent dosage: 0.100 g/100 mL; with ATAC: pH: 6-9; time of equilibration: 1.5 h and sorbent dosage: 0.125 g/100 mL; and with PCAC: pH: 6-9; time of equilibration: 2.0 h and sorbent dosage 0.50 g/100 mL. Spent adsorbents can be regenerated and reused until four cycles with minimal loss of adoption capacities. Thermodynamic studies revealed that the sorption is spontaneous and endothermic in nature. Further, the ΔH value for CDAC is 30.156 KJ/mol; it indicates the strong chemisorption and may be through reduction to Cu+/Cu and/or complex formation between Cu2+ and functional groups of the adsorbent. The ΔH values of other two activated carbons, ATAC and PCAC, indicated that the sorption is mainly physical with strong inclination towards chemical nature. Positive ΔS values of all the three sorbents, emphasizes the disorder or randomness at the solid-liquid interface and hence favourable conditions for more penetration of Cu2+ into the surface layers of the adsorbent and hence, more removal of Cu2+ ions. The negative ΔG values indicate that the sorption forces are good enough to cross the potential barrier at the solid-liquid interface and hence the process is spontaneous. The prepared three activated carbons were also successfully applied to industrial effluent and polluted lake samples.

ИССЛЕДОВАНИЕ ЭКОТОКСИЧНОСТИ ОТРАБОТАННЫХ АДСОРБЕНТОВ В ПРОЦЕССЕ ХРАНЕНИЯ

ИССЛЕДОВАНИЕ ЭКОТОКСИЧНОСТИ ОТРАБОТАННЫХ АДСОРБЕНТОВ В ПРОЦЕССЕ ХРАНЕНИЯ

Catalytic Conversion of Xylose and Xylan into Furfural Over Cr3+/P-SBA-15 Catalyst Derived from Spent Adsorbent

The mesoporous SBA-15 has long been used as an adsorbent for the removal of toxic metal ions. Achieving secondary utilize of spent adsorbent is undoubtedly an advisible option for environmental protection and recycling economy. In the present study, phosphoric acid-modified SBA-15 (P-SBA-15) was found to be an available adsorbent, and the composites (Cr3+/P-SBA-15) formed after adsorption of Cr3+ ions have the ability to efficiently catalyze the conversion of xylose and xylan into furfural. The physicochemical properties of the Cr3+/P-SBA-15 composites were characterized, and the effects of various reaction parameters on their catalytic performance were also investigated. Among the Cr3+/P-SBA-15 composites with different Cr3+ contents, the (0.25)Cr3+/P-SBA-15 composite not only achieved excellent 91% and 58% furfural yields from xylose and xylan, but also had almost constant catalytic performance after five cycles. The findings herein provided a reference for achieving high yields of furfural and reuse of spent adsorbents.

Reactivation of spent S-Zorb adsorbents for gasoline desulfurization

Spent adsorbents from the S-Zorb technology are hazardous wastes. Reactivating and recycling the spent S-Zorb adsorbents is of great significance to environmental protection. However, no report concerning this subject has been found yet. Herein, we have developed an acid-base coupling method to reactivate the spent S-Zorb adsorbents. To achieve this goal, the deactivation factors of the adsorbents were studied. The results show that the formation of Zn2SiO4 phase, which results in loss of active phase (ZnO) for sulfur storage, is the main deactivation factor. The acid-base coupling method can transform Zn2SiO4 into soluble Zn2+ via nitric acid, followed by precipitation as Zn(OH)2 with sodium hydroxide addition. After calcination, the loss of ZnO can be supplemented. The newly formed ZnO bears a willow-leaf shape that is remarkably different from the original one. Also, it has smaller particle size compared to that of fresh adsorbents. Of note is that mesopores and Lewis acid sites are created over the adsorbents via the acid-base coupling method, accelerating the mass transfer and conversion of sulfur compounds. Carbon deposited over the adsorbent surface is removed and metal sulfides (ZnS and NiS) are oxidized into metal oxides (ZnO and NiO) via calcination of the spent adsorbents. The desulfurization efficiency of the reactivated adsorbent is superior to that of the regenerated adsorbent and reaches a level comparable to that of the fresh adsorbent in gasoline desulfurization.

Synthesis and characterization of amidoxime modified chitosan/bentonite composite for the adsorptive removal and recovery of uranium from seawater

A novel amidoxime functionalized adsorbent, poly(amidoxime)-grafted-chitosan/bentonite composite [P(AO)-g-CTS/BT] was prepared by in situ intercalative polymerization of acrylonitrile (AN) and 3-hexenedinitrile (3-HDN) onto chitosan/bentonite composite using ethylene glycol dimethacrylate (EGDMA) as cross linking agent and potassium peroxy disulphate (K2S2O8) as free radical initiator. The adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), BET surface area analyser and X-ray photoelectron spectroscopy (XPS). Nitrile groups from two monomers converted to amidoxime groups and therefore, increases the adsorption efficiency of uranium(VI) [U(VI)] from seawater. The optimum pH for U(VI) adsorption was found to be 8.0. The adsorbent dosage of 2.0 g/L was sufficient for the complete removal of U(VI) from seawater. The kinetic data fitted well with pseudo-second-order kinetic model which assumes the presence of chemisorption. The equilibrium attained within 60 min and well agreement of equilibrium data with Langmuir adsorption model confirms monolayer coverage of U(VI) onto P(AO)-g-CTS/BT. The maximum adsorption capacity was found to be 49.09 mg/g. Spent adsorbent was effectively regenerated using 0.1 N HCl. Six cycles of adsorption-desorption experiments were conducted to study the practical applicability and repeated use of the adsorbent. The feasibility of the adsorbent was also tested using natural seawater. The results show that P(AO)-g-CTS/BT is a promising adsorbent for the removal of U(VI) from seawater.

Adsorption behaviour of 2-mercaptobenzamide modified itaconic acid-grafted-magnetite nanocellulose composite for cadmium(II) from aqueous solutions

In the present study, a cellulose based adsorbent, P(MB-IA)-g-MNCC was synthesized by graft co-polymerization of itaconic acid onto MNCC using EGDMA as crosslinking agent and K2S2O8 as free radical initiator. P(MB-IA)-g-MNCC was characterized by FTIR, XRD, SEM, TG and VSM. Cd(II) adsorption occurs maximum at pH 6.0. Kinetic and isotherm data were described using pseudo-second-order kinetic model and Sips isotherm model, respectively. Adsorbent dosage of 2.0g/L was sufficient for the complete removal of Cd(II) ions from aqueous solutions. The maximum adsorption capacity of P(MB-IA)-g-MNCC was found to be 262.27mg/g. Spent adsorbent was effectively regenerated using 0.1M HCl.

Designing recyclable Cu/ZrSBA-15 for efficient thiophene removal

Adsorptive desulfurization (ADS) is an effective method for the selective capture of thiophenic sulfur compounds, and the ADS capacity of an adsorbent has been demonstrated to strongly depend on the dispersion degree of active species. Herein, series of zirconia-modified SBA-15 (ZrSBA-15) framework with uniformly dispersed Cu sites have been prepared via a urea-assisted homogeneous deposition strategy, aiming for efficient adsorption towards thiophene. The resultant materials were thoroughly characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectra (DRS) analysis techniques. It was revealed that the Cu species were highly dispersed inside the ordered ZrSBA-15 framework with platelet morphology, rather than aggregation outside the surface, leading to excellent adsorption capacity for thiophene (up to 9.35 mg/g at 50 °C). The adsorption kinetics and isotherm data can be well described by the pseudo-second-order kinetics model and the Langmuir isotherm, respectively. Spent adsorbent can be regenerated by simple heating treatment in N2 at 500 °C, without obvious losing of thiophene adsorption capacity even after eight cycles.

Effective removal of mercury(II) ions from chlor-alkali industrial wastewater using 2-mercaptobenzamide modified itaconic acid-grafted-magnetite nanocellulose composite

A novel adsorbent, 2-mercaptobenzamide modified itaconic acid-grafted-magnetite nanocellulose composite [P(MB-IA)-g-MNCC] was synthesized for adsorbing mercury(II) [Hg(II)] ions selectively from aqueous solutions. Fourier transforms infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric studies were performed to characterize the adsorbent. The optimum pH for Hg(II) adsorption was found to be 8.0, and the adsorption attained equilibrium within 60min. The kinetic data were found to follow pseudo-second-order which assumes the ion exchange followed by complexation mechanism. The temperature dependence indicates an exothermic process. The well agreement of equilibrium data with Freundlich adsorption model confirms the multilayer coverage of Hg(II) onto P(MB-IA)-g-MNCC. The maximum adsorption capacity was found to be 240.0mg/g. Complete removal of Hg(II) from aqueous solution was possible with an adsorbent dosage of 2.0g/L. Spent adsorbent was effectively degenerated with 0.1M HCl. The present investigation shows that P(MB-IA)g-MNCC is a promising adsorbent for the removal and recovery of Hg(II) ions from aqueous solutions.

Investigation of the Extraction of Hemoglobin by Adsorption onto Nanocellulose-Based Superabsorbent Composite Having Carboxylate Functional Groups from Aqueous Solutions: Kinetic, Equilibrium, and Thermodynamic Profiles

We have developed a superabsorbent composite based on cellulose, namely poly(acrylic acid)-modified poly(glycidylmethacrylate)-grafted nanocellulose (PAPGNC), via graft copolymerization technique, and it is well characterized. The adsorption of a globular protein, hemoglobin (Hb), onto PAPGNC was studied by batch-adsorption technique. The optimum pH for Hb adsorption was found to be 6.7, and the adsorption attained equilibrium within 3.0 h. The kinetic data were found to follow pseudo-second-order model, and the equilibrium data were found to agree with the Langmuir isotherm model. The maximum adsorption capacity of PAPGNC was found to be 119.92 mg/g at 30 °C. The adsorption capacity of PAPGNC toward Hb was found to increase with an increase in temperature. Spent adsorbent was effectively degenerated using 0.1 M KSCN solution without a loss in adsorption capacity, even after four cycles. The present investigation shows that PAPGNC can be developed as an efficient adsorbent for the extraction and recovery of Hb from aqueous solutions.