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This work describes the preparation of new chelating material from mercerized cellulose. The first part treats the chemical modification of non-mercerized cellulose (cell 1) and mercerized cellulose (cell 2) with succinic anhydride. Mass percent gains (mpg) and degree of succinylation (DS) of cell 3 (from cell 1) and cell 4 (from cell 2) were calculated. Cell 4 in relation to cell 3 exhibited an increase in mpg and in the concentration of carboxylic functions of 68.9% and 2.8 mmol/g, respectively. Cells 5 and 6 were obtained by treatment of cells 3 and 4 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part compares the adsorption capacity of cells 5 and 6 for Cu2+, Cd2+, and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. Cell 6 in relation to cell 5 exhibited an increase in Qmax for Cu2+ (30.4 mg/g), Cd2+ (86.0 mg/g) and Pb2+ (205.9 mg/g).

The contamination of surface and groundwater with arsenic is an urgent problem in many countries where the population does not have any other water sources. A new renewable/recoverable sugarcane bagasse anion adsorbent (SBAA) for arsenic removal was prepared using a greener, cleaner, and sustainable synthesis method in a mini-pilot reactor. SBAA was prototyped for the treatment of arsenic-contaminated groundwater. Tests carried out with the prototype connected to household clay ceramic water filters showed that SBAA achieved 95 ± 3% arsenic removal, reaching arsenic levels below the WHO's limit of 10 µg L−1. SBAA obtained the NSF/ANSI 61–2016 safety certification, which allows its safe and commercial use. Comparing the performance of the SBAA with commercial materials demonstrates its potential to compete with other technologies in the market. The SBAA is efficient, even in the presence of interfering contaminants. The technology validation classified it at technology readiness level 4. The financial analysis of the proposed business model considered a total sale of 180,000 units in 5 y (semi-industrial process), 4% of the Latin American market, and a sales price of USD $6.95 per unit. A Net present value of USD $52,690.51, internal return rate of 28%, payback of 3.0 y, discounted payback of 3.4 y, and breakeven point of 1.6 y were obtained. The upscaling potential of the SBAA technology was demonstrated, considering technical and market aspects for the development of competitive renewable-based technologies not yet available in the market for the treatment of water contaminated with arsenic. [Display omitted] • Biosorbent (SBAA) prepared under circular economy and cleaner production concepts. • SBAA can solve arsenic-contaminated drinking water in developing countries. • Upscaling and business model show SBAA is technically and economically viable. • SBAA underwent several tests for its safety certification and commercialization. • A prototype was developed for using SBAA in household water filtration systems. [ABSTRACT FROM AUTHOR]

In this study, four different adsorbent materials: commercial powdered activated carbon (PAC) from pine tree (PAC-I) and coconut shell (PAC-III) agricultural crop wastes, coal (PAC-II), and carbon nanotubes (CNT) were tested and compared for the removal of sulfamethoxazole (SMX) from spiked aqueous solutions. The kinetic, extrathermodynamic, and thermodynamic parameters for the adsorption of SMX on PACs and CNT were also determined. The results indicate that PAC-I was the best adsorbent for SMX adsorption. SMX adsorption was only favorable with PAC-I and CNT, leading to Gibbs free energies in the range of −39 to −44 kJ mol −1 and showing that the adsorption process was spontaneous in all temperature ranges (15–45 °C) tested. Langmuir model best described SMX adsorption on PAC-I and led to maximum adsorption capacity of ∼131 mg g −1 (at 25 °C), which was ∼4.6 times higher than that observed for CNT. The mechanism of SMX adsorption on PAC-I and CNT was suggested with basis on thermodynamic and extrathermodynamic parameters. The kinetic studies showed the pseudo-second-order model best described SMX adsorption, yielding k 2 values of 0.0035 and 0.0016 g mg −1 min −1 for PAC-I and CNT, respectively. [ABSTRACT FROM AUTHOR]

In this study sugarcane bagasse was modified with succinic anhydride and EDTA dianhydride to obtain SCB 2 and EB adsorbents, respectively. These adsorbents were used to remove etherdiamine, which is used for iron ore flotation from single aqueous solutions. The removal and recovery of etherdiamine is important for environmental and economic reasons due to its toxicity and high cost. The results demonstrated that adsorption of etherdiamine by SCB 2 and EB was better fitted by a pseudo-second-order kinetic model than pseudo-first-order and Elovich models. Adsorption isotherms were better fitted by the Langmuir model rather than the Freundlich, Sips, and Temkin models. The maximum adsorption capacities (Q max) of SCB 2 and EB for etherdiamine adsorption were found to be 869.6 and 1203.5 mg/g, respectively. The calculated ΔG° values for adsorption of etherdiamine on SCB 2 (−22.70 kJ/mol) and EB (−19.10 kJ/mol) suggested that chemisorption is the main mechanism by which etherdiamine is removed from the aqueous solution for both adsorbents. The high Q max values showed that SCB 2 and EB are potential adsorbents for recovering the etherdiamine and treating effluents produced from iron ore flotation. [Copyright &y& Elsevier]

Abstract: In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be −22.50 and −24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process. [Copyright &y& Elsevier]

Abstract: This work describes the preparation of a new chelating material derived from wood sawdust, Manilkara sp., and not only the use of a new support, but also a chemically modified sugarcane bagasse synthesized in our previous work to remove Zn2+ from aqueous solutions and electroplating wastewater. The first part describes the chemical modification of wood sawdust and sugarcane bagasse using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent in order to introduce carboxylic acid and amine functional groups into these materials. The obtained materials such as the modified sugarcane bagasse, EB, and modified wood sawdust, ES were then characterized by infrared spectroscopy (IR) and CHN. The second part evaluates the adsorption capacity of Zn2+ by EB and ES from aqueous single metal solutions and real electroplating wastewater, which concentration was determined through direct titration with EDTA and inductively coupled plasma (ICP-OES). Adsorption isotherms were developed using Langmuir model. Zn2+ adsorption capacities were found to be 80mg/g for ES and 105mg/g for EB whereas for the industrial wastewater these values were found to be 47mg/g for ES and 45mg/g for EB. Zn2+ adsorption in the wastewater was found to be lower than in Zn2+ spiked solution due to the competition between other cations and/or interference of other ions, mainly Ca2+ and Cl− that were present in the wastewater. [Copyright &y& Elsevier]

Abstract: In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca2+ and Mg2+ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca2+ and Mg2+ ions ranging from 15.6 to 54.1mg/g and 13.5 to 42.6mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals. [Copyright &y& Elsevier]

Abstract: This study describes the preparation of two new chelating materials, MMSCB 3 and 5, derived from succinylated twice-mercerized sugarcane bagasse (MMSCB 1). MMSCB 3 and 5 were synthesized from MMSCB 1 using two different methods as described by . In the first method MMSCB 1 was activated with 1,3-diisopropylcarbodiimide and in the second with acetic anhydride (to form an internal anhydride) and later both were reacted with triethylenetetramine in order to obtain MMSCB 3 and 5. New obtained materials were characterized by mass percent gain, concentration of amine groups, FTIR, and elemental analysis. MMSCB 3 and 5 showed mass percent gain of 19.9 and 57.1%, concentration of amine groups of 2.0 and 2.1mmol/g, and nitrogen content of 5.8 and 4.4%. The capacity of MMSCB 3 and 5 to adsorb Cu2+, Cd2+, and Pb2+ from aqueous single metal ion solutions was evaluated at different contact times, pHs, and initial metal ion concentrations. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacities of MMSCB 3 and 5 for Cu2+, Cd2+, and Pb2+ were found to be 59.5 and 69.4, 86.2 and 106.4, 158.7 and 222.2mg/g, respectively. [Copyright &y& Elsevier]

Abstract: This work describes the preparation of new chelating materials derived from cellulose and sugarcane bagasse for adsorption of Cu2+, Cd2+, and Pb2+ ions from aqueous solutions. The first part involved the mercerization treatment of cellulose and sugarcane bagasse with NaOH 5mol/L. Non- and mercerized cellulose and sugarcane bagasse were then reacted with ethylenediaminetetraacetic dianhydride (EDTAD) in order to prepare different chelating materials. These materials were characterized by mass percent gain, X-ray diffraction, FTIR, and elemental analysis. The second part consisted of evaluating the adsorption capacity of these modified materials for Cu2+, Cd2+, and Pb2+ ions from aqueous single metal solutions, whose concentration was determined by atomic absorption spectroscopy. These materials showed maximum adsorption capacities for Cu2+, Cd2+, and Pb2+ ions ranging from 38.8 to 92.6mg/g, 87.7 to 149.0mg/g, and 192.0 to 333.0mg/g, respectively. The modified mercerized materials showed larger maximum adsorption capacities than modified non-mercerized materials. [Copyright &y& Elsevier]

Abstract: This study describes the preparation of two new chelating materials derived from succinylated mercerized cellulose (cell 1). Cell 1 was activated through two different methods by using diisopropylcarbodiimide and acetic anhydride (to form an internal anhydride) and reacted with triethylenetetramine in order to obtain cell 2 and 4. New modified celluloses were characterized by mass percent gain, concentration of amine functions, elemental analysis, and infrared spectroscopy. Cell 2 and 4 showed degrees of amination of 2.8 and 2.3mmol/g and nitrogen content of 6.07% and 4.61%, respectively. The capacity of cell 2 and 4 to adsorb Cu2+, Cd2+, and Pb2+ ions from single aqueous solutions were examined. The effect of contact time, pH, and initial concentration of metal ions on the metal ions uptake was also investigated. Adsorption isotherms were well fitted by the Langmuir model. The maximum adsorption capacity of cell 2 and 4 were found to be 56.8 and 69.4mg/g for Cu2+; 68.0 and 87.0mg/g for Cd2+; and 147.1 and 192.3mg/g for Pb2+, respectively. [Copyright &y& Elsevier]

Abstract: This work describes the preparation of new chelating material from mercerized sugarcane bagasse. The first part treats the chemical modification of non-mercerized sugarcane bagasse (SCB) and twice-mercerized sugarcane bagasse (MMSCB) with succinic anhydride. Mass percent gains (mpg) and degrees of succinylation (DS) of succinylated non- and twice-mercerized sugarcane bagasse 1 (SCB 1 and MMSCB 1) were calculated. MMSCB 1 exhibited an increase in mpg and DS of 49.2% and 0.9mmol/g in relation to SCB 1. SCB 2 and MMSCB 2 were obtained by treatment of MMSCB 1 and SCB 1 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part evaluates and compares the adsorption capacity of SCB 2 and MMSCB 2 for Cu2+, Cd2+ and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. MMSCB 2 exhibited an increase in Q max for Cd2+ (43.6mg/g) and Pb2+ (83.3mg/g) in relation to SCB 2. [Copyright &y& Elsevier]

Technical lignin (TL) is a solid waste generated in industrial activities including pulp and paper mills and second-generation (2G) biorefineries. After isolation processes, TL is available in large quantities and has favorable compositional characteristics to produce high-performance activated carbons (ACs), such as low amount of residual carbohydrates, high reactivity due to the presence of different functional groups, and high aromatic carbon content. The value of the AC market is projected to reach US$ 7 billion by 2028, led by the water treatment sector. This work provides a brief overview of the status quo in the production of new adsorbents from TL, focusing on biorefineries, together with a bibliometric and patentometric survey. This evidenced a scarcity of publications on this topic, with the primary focus being on chemical modification of TL. A notable increase was observed in the production of ACs for electrochemical applications. Only a few patents were found on the subject, with China predominating technological development in this area. The findings revealed a technical-scientific-economic potential that has been largely unexplored, as no TL-derived AC from 2G biorefineries has yet been produced and applied in water treatment. Hence, there is excellent potential for the wider commercialization of AC produced from TL, representing an excellent opportunity to recycle TL and support the bio-based circular carbon economy, while also contributing to carbon emission neutrality. The marketing of high-performance ACs produced from TL could make biorefineries more profitable and less sensitive to market price fluctuations, while becoming carbon-neutral multiproduct platforms. [Display omitted] • Technical lignin (TL) has untapped technical-scientific-economic potential. • Production of activated carbon is a technological way to add value to TL. • Bibliometrics and patentometrics indicate a scarcity of value-added TL products. • Biorefineries as key contributors to carbon neutral emissions in the energy sector. • New opportunities and challenges identified for excess TL in 2G ethanol plant. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Sugarcane bagasse cellulose mixed ester succinate phthalate (SBSPh) was synthesized by a novel one-pot reaction method. The effects of temperature, time and mole fraction of succinic anhydride (χ SA) on the responses weight gain (wg), number of carboxylic acid groups (n T,COOH), and adsorption capacity (q) of Co2+ and Ni2+ were evaluated by a 23 experimental design. The chemical structure of the material was elucidated by Fourier transform infrared, 13C Multiple Cross-Polarization solid-state NMR spectroscopy and 1H NMR relaxometry. The best SBSPh synthesis condition (100 °C, 11 h, χ SA of 0.2) yielded a wg of 59.1%, n T,COOH of 3.41 mmol g−1, and values of q Co 2+ and q Ni 2+ of 0.348 and 0.346 mmol g−1, respectively. The Sips model fitted better the equilibrium data, and the maximum adsorption capacities (pH 5.75 and 25 °C) estimated by this model were 0.62 and 0.53 mmol g−1 for Co2+ and Ni2+, respectively. The Δ ads H ° values estimated by isothermal titration calorimetry were 8.43 and 7.79 kJ mol−1 for Co2+ and Ni2+, respectively. Desorption and re-adsorption efficiencies were evaluated by a 22 experimental design, which showed that SBSPh adsorbent can be recovered and reused without significant loss of adsorption capacity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Bifunctionalized chitosan(C4) was synthesized for removal of both Cu2+ and Cr6+. • C4 was insoluble in water in a pH range of 1–10. • The maximum adsorption capacity of C4 for Cu2+ adsorption at pH 5.5 was 2.60 mmol/g. • The maximum adsorption capacity of C4 for Cr6+ adsorption at pH 2.0 was 3.50 mmol/g. • The re-adsorption efficiency of C4 was 106% for Cu2+ and 44% for oxyanions of Cr6+. Abstract This study describes the chemical modification of chitosan to produce a novel bifunctionalized adsorbent material (C4) for the removal of Cu2+ and oxyanions of Cr6+ from a single aqueous solution. The chemical modifications allowed C4 to be insoluble under acidic conditions, improving the chemical properties of the modified chitosan in aqueous solution. C4 adsorbent was synthesized by reaction of the amino group of chitosan with 2-pyridinecarboxaldehyde, a reduction of imine group, followed by esterification with EDTA dianhydride (EDTAD). C4 was characterized by solid-state 13C nuclear magnetic resonance, infrared spectroscopy, and elemental analysis. The adsorption studies of Cu2+ and oxyanions of Cr6+ in a batch mode were evaluated as a function of the contact time (kinetics), solution pH, and initial metal ion concentration. The maximum adsorption capacities (Q max) of C4 for the adsorption of Cu2+ (pH 5.5) and Cr6+ (pH 2.0) were 2.60 and 3.50 mmol/g, respectively. The reusability of the recovered C4 adsorbent was also evaluated. [ABSTRACT FROM AUTHOR]

Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g −1 at pH 4.5, and 1.734 and 1.230 mmol g −1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol −1 , indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions. [ABSTRACT FROM AUTHOR]

In the third part of this series of studies, the adsorption of the basic textile dyes auramine-O (AO) and safranin-T (ST) on a carboxylated cellulose derivative (CTA) were evaluated in mono- and bi-component spiked aqueous solutions. Adsorption studies were developed as a function of solution pH, contact time, and initial dye concentration. Adsorption kinetic data were modeled by monocomponent kinetic models of pseudo-first- (PFO), pseudo-second-order (PSO), intraparticle diffusion, and Boyd, while the competitive kinetic model of Corsel was used to model bicomponent kinetic data. Monocomponent adsorption equilibrium data were modeled by the Langmuir, Sips, Fowler-Guggenhein, Hill de-Boer, and Konda models, while the IAST and RAST models were used to model bicomponent equilibrium data. Monocomponent maximum adsorption capacities for AO and ST at pH 4.5 were 2.841 and 3.691 mmol g −1 , and at pH 7.0 were 5.443 and 4.074 mmol g −1 , respectively. Bicomponent maximum adsorption capacities for AO and ST at pH 7.0 were 1.230 and 3.728 mmol g −1 . Adsorption enthalpy changes (Δ ads H ) were obtained using isothermal titration calorimetry. The values of Δ ads H ranged from −18.83 to −5.60 kJ mol −1 , suggesting that physisorption controlled the adsorption process. Desorption and re-adsorption of CTA was also evaluated. [ABSTRACT FROM AUTHOR]

Carbonaceous materials have been extensively studied as highly efficient adsorbents for the removal of dyes from wastewater. However, investigations of thermodynamic aspects of the interactions between these materials and dyes remain scarce. This paper describes the thermodynamics of the interactions between the Ponceau 4R (PR), Congo Red (CR), and Allura Red (AR) dyes and multi-walled carbon nanotubes (MWCNTs). The interactions between the dyes and activated carbon (AC) were also evaluated for comparison. The investigation used a combination of adsorption isotherms and isothermal titration nanocalorimetry (ITC) measurements, and a thermodynamic approach provided full characterization of the adsorption process. For both MWCNT and AC, the amount of adsorbed dye ( Γ D ) increased in the order Γ D (PR) < Γ D (AR) < Γ D (CR), and the adsorption capacity normalized by the adsorbent specific area was up to 5.6 times higher for MWCNT. The maximum amount adsorbed ( Γ D,max ) reached values of up to 2.00 μmol m −2 for CR adsorption on MWCNT. For both adsorbents, the process of dye adsorption was enthalpically driven and entropically unfavorable. All the thermodynamic parameters depended on the surface coverage and the structures of both dye and adsorbent. The adsorption enthalpy change (Δ ads H ) and entropy change (TΔ ads S ref ) values were higher than −137.0 kJ mol −1 and −114.2 kJ mol −1 , respectively. In addition to the structural differences between MWCNT and AC, the ITC data suggested that the adsorption sites are heterogeneous and that the dyes preferentially adsorb on the more hydrophilic sites on the adsorbent surfaces. [ABSTRACT FROM AUTHOR]

Cellulose (Cel) and sugarcane bagasse (SB) were oxidized with an H 3 PO 4 -NaNO 2 mixture to obtain adsorbent materials with high contents of carboxylic groups. The oxidation reactions of Cel and SB were optimized using design of experiments (DOE) and response surface methodology (RSM). The optimized synthesis conditions yielded Cox and SBox with 4.8 mmol/g and 4.5 mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state 13 C NMR. The adsorption of the model cationic dyes crystal violet (CV) and auramine-O (AO) on Cox and SBox in aqueous solution was investigated as a function of the solution pH, the contact time and the initial dye concentration. The adsorption of CV and AO on Cox was described by the Elovich equation and the pseudo-first-order kinetic model respectively, while the adsorption of CV and AO on SBox was described by the pseudo-second-order kinetic model. Adsorption isotherms were well fitted by the Langmuir and Konda models, with maximum adsorption capacities ( Q max ) of 1117.8 mg/g of CV and 1223.3 mg/g of AO on Cox and 1018.2 mg/g of CV and 682.8 mg/g of AO on SBox. Desorption efficiencies were in the range of 50–52% and re-adsorption capacities varied from 65 to 81%, showing the possibility of reuse of both adsorbent materials. [ABSTRACT FROM AUTHOR]

A new carboxylated cellulose derivative (CTA) was prepared from the esterification of cellulose with 1,2,4-Benzenetricarboxylic anhydride. CTA was characterized by percent weight gain ( pwg ), amount of carboxylic acid groups ( n COOH ), elemental analysis, FTIR, TGA, solid-state 13 C NMR, X-ray diffraction (DRX), specific surface area, pore size distribution, SEM and EDX. The best CTA synthesis condition yielded a pwg and n COOH of 94.5% and 6.81 mmol g −1 , respectively. CTA was used as an adsorbent material to remove Co 2+ , Cu 2+ and Ni 2+ from monocomponent spiked aqueous solution. Adsorption studies were developed as a function of the solution pH, contact time and initial adsorbate concentration. Langmuir model better fitted the experimental adsorption data and the maximum adsorption capacities estimated by this model were 0.749, 1.487 and 1.001 mmol g −1 for Co 2+ , Cu 2+ and Ni 2+ , respectively. The adsorption mechanism was investigated by using isothermal titration calorimetry. The values of Δ ads H ° were in the range from 5.36 to 8.09 kJ mol −1 , suggesting that the mechanism controlling the phenomenon is physisorption. Desorption and re-adsorption studies were also performed. Desorption and re-adsorption efficiencies were closer to 100%, allowing the recovery of both metal ions and CTA adsorbent. [ABSTRACT FROM AUTHOR]

This study describes the synthesis of a new chitosan derivative (C2) with zwitterionic characteristics and its use for the removal of cationic species Cu 2+ , Co 2+ , and Ni 2+ and anionic species of Cr 6+ in a single aqueous solution. The new adsorbent was synthesized by quaternization of the amine group of chitosan and esterification of hydroxyl groups with EDTA dianhydride. These combined reactions gave both cationic and anionic characteristics to C2 with the release of quaternary ammonium groups and carboxylic groups. The capacity of C2 to adsorb Cu 2+ , Co 2+ , Ni 2+ , and oxyanions of Cr 6+ was evaluated in a batch process with different contact times, pH values, and initial concentrations. Adsorption isotherms were best fitted to the Langmuir and Sips models. The maximum adsorption capacities ( Q max ) of C2 for adsorption of Cu 2+ , Co 2+ , Ni 2+ , and Cr 6+ were 0.698, 1.125, 0.725, and 1.910 mmol/g, respectively. The Δ ads G ° values were in the range from −20 to −28 kJ/mol. These values suggest a mixed mechanism controlling adsorption. Desorption studies using an aqueous solution consisting of 0.1 mol/L HNO 3 were carried out. The reusability of the recovered C2 adsorbent after desorption was also evaluated. [ABSTRACT FROM AUTHOR]

This study describes, in detail, the chemical modification of sugarcane bagasse with phthalic anhydride to produce a carboxylate-functionalized sugarcane bagasse (SPA). The optimized modification conditions yielded SPA with a percent weight gain of 77.08% and an amount of carboxylic acid groups of 4.76 mmol/g. The SPA was characterized by PZC, FTIR, elemental analysis, TGA, and SEM-EDX. An SPA adsorbent was used to remove Co 2+ , Cu 2+ , and Ni 2+ from aqueous solution in mono- and multicomponent systems in batch mode. The adsorption kinetics followed a pseudo-second-order model. The adsorption rate constants assumed the following order: k 2,Co 2+ > k 2,Ni 2+ > k 2,Cu 2+ . Four mono- and multicomponent isotherm models were used to model the adsorption data. Monocomponent data were well described by the Langmuir model, whereas bicomponent data were well described by the modified extended Langmuir and P -Factor models. The maximum adsorption capacities ( Q max,mono ) for the Langmuir model were 0.561, 0.935, and 0.932 mmol/g for Co 2+ , Cu 2+ , and Ni 2+ , respectively. Adsorption in bicomponent systems revealed that Cu 2+ suppressed the adsorption of Co 2+ and Ni 2+ , whereas Ni 2+ suppressed the adsorption of Co 2+ . Desorption studies revealed that the SPA adsorbent could be fully desorbed with a 1 mol/L HNO 3 solution. [ABSTRACT FROM AUTHOR]

A new carboxylated-functionalized sugarcane bagasse (STA) was prepared through the esterification of sugarcane bagasse with trimellitic anhydride. The optimized synthesis conditions yield STA with a percent weight gain of 73.9% and the number of carboxylic acid groups accounted for 3.78 mmol/g. STA was characterized by FTIR, elemental analysis, TGA, PZC, and SEM. Adsorption kinetics followed a pseudo-second-order model. The adsorption rate constant showed the following order: k 2,Ni 2+ > k 2,Cu 2+ > k 2,Co 2+ . Four mono- and multi-component isotherm models were used to model the adsorption systems. Monocomponent experimental data were fitted to Langmuir and Sips models; whereas, multicomponent data were fitted to modified extended Langmuir and P -factor models. The maximum adsorption capacities ( Q max,mono ) obtained from the Langmuir model were 1.140, 1.197, and 1.563 mmol/g for Co 2+ , Cu 2+ , and Ni 2+ , respectively. The competitive studies demonstrated that the multicomponent adsorption capacity ( Q max,multi ) was smaller than Q max,mono , as a result of the interaction between the metal ions. Desorption studies showed that all metal ions could be fully desorbed from STA. [ABSTRACT FROM AUTHOR]

A new carboxylate-functionalized sugarcane bagasse (SMA) was prepared via a solvent-free procedure involving esterification of sugarcane bagasse with Meldrum's acid. The optimized conditions provided SMA with a percent weight gain of 86.0% and 4.69 ± 0.20 mmol/g of carboxylic acid groups. SMA was characterized by FTIR, TGA, elemental analysis and SEM. Kinetic experiments showed that the amount of crystal violet adsorbed increased with increasing temperature and equilibrium was reached at 12 h. Adsorption kinetics followed a pseudo-second-order model. The Arrhenius and Eyring models were used to obtain the activation energy and changes in free energy, enthalpy, and entropy of activation for the adsorption process. The calculated activation energy (14.14 kJ/mol) suggested physical adsorption of CV onto SMA. The equilibrium data were well fitted to the Langmuir and Sips isotherms. Maximum adsorption capacity was 692.1 mg/g at 45 °C. Thermodynamic parameters such as changes in free energy, enthalpy and entropy were also determined. [ABSTRACT FROM AUTHOR]