This study describes the synthesis of a new bioadsorbent from chitosan using ethylenediaminetetraacetic dianhydride (EDTAD) as a modifying agent and its successful application for removal of a cationic ion (copper (II) (Cu 2+ )) and oxyanions of chromium (VI) (Cr 6+ ) from single-component aqueous systems. The new multifunctionalised chitosan derivative (C1) was produced through chemical modification of the primary hydroxyl function of chitosan with EDTAD to introduce carboxylic and tertiary amine functional groups, maintaining the secondary amines on the chitosan surface. Such a transformation was important not only to increase the adsorptive potential of chitosan but also to allow C1 to be used in acidic media, thus solving the problem of solubility of most chitosan derivatives. C1 was characterised by spectroscopic methods. The effects of solution pH, contact time and initial solute concentration on the removal of copper (II) and chromium (VI) by C1 were investigated in aqueous solutions. C1 showed an experimental maximum adsorption capacity of 106 mg/g for copper (II) and 194 mg/g for chromium (VI).

This study describes the synthesis of a new bioadsorbent from chitosan using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent and its successful aplication for removal of cationic ion (Cu(II)) and oxyanion (Cr(VI)) from single component aqueous systems. The new multifunctionalized chitosan derivative (C1) was produced through chemical modification of primary hydroxyl function of chitosan with EDTAD to introduce carboxylic and tertiary amine functional groups, maintaining the secondary amines on the chitosan surface. Such a transformation was important to increase the adsorptive potential of chitosan but also to allow C1 to be used in acidic media, thus solving the problem of solubility of most chitosan derivatives. C1 was characterized by spectroscopic methods. The effects of solution pH, contact time, and initial solute concentration on removal of Cu(II) and Cr(VI) by C1 were investigated in aqueous solutions. C1 showed experimental maximum adsorption capacity of 106 mg g(-1) for Cu(II) and 194 mg g(-1) for Cr(VI).

This study describes the synthesis of a new bioadsorbent with zwitterionic characteristics and its successful application for removal of a cationic dye (crystal violet, CV) and an anionic dye (orange II, OII) from single component aqueous systems. The new bi-functionalized cellulose derivative (MC3) was produced by chemical modification of cellulose with succinic anhydride and choline chloride to introduce carboxylic and quaternary ammonium functional groups on the cellulose surface. MC3 was characterized by several wet chemical and spectroscopic methods. The effects of solution pH, contact time, and initial solute concentration on removal of CV and OII by MC3 were investigated. Studies of the desorption and re-adsorption of the dyes were also carried out. The isotherms for adsorption of CV and OII on MC3 were satisfactorily fitted using the Konda and Langmuir models. MC3 showed experimental maximum adsorption capacities of 2403 mg g-1 for CV and 201 mg g-1 for OII. The desorption and re-adsorption results showed that MC3 could be reused in successive adsorption cycles, which is essential for minimizing process costs and waste generation. The findings showed that MC3 is a versatile biosorbent capable of efficiently removing both cationic and anionic dyes.

In this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X-ray diffraction, elemental analysis X-ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo-second-order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.

This work describes the application of raw and chemically modified cellulose and sugarcane bagasse for ipso-hydroxylation of aryl boronic acids in environmentally friendly reaction conditions. The catalytic efficiency of five support-[Cu] materials was compared in forming phenols from aryl boronic acids. Our investigation highlights that the CEDA-[Cu] material (6-deoxy-6-aminoethyleneamino cellulose loaded with Cu) leads to the best results under very mild reaction conditions. The optimized catalytic sequence, allowing a facile transformation of boronic acids to phenols, required the mandatory and joint presence of the support, Cu2O, and KOH at room temperature. CEDA-[Cu] was characterized using 13C solid-state NMR, ICP, and FTIR. The use of CEDA-[Cu] accounts for the efficacious synthesis of variously substituted phenol derivatives and presents very good recyclability after five catalytic cycles.

The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g(-1) for Cu(II) and 3.86 and 0.98 mmol g(-1) for Cr(VI), respectively. The reuse of C4 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower readsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.

Batch and continuous adsorption of Co2+ and Cu2+ from aqueous solutions by oxidized sugarcane bagasse (SBox) and oxidized cellulose (Cox) were investigated. The oxidation reaction of sugarcane bagasse and cellulose was made with a mixture of H3PO4‒NaNO2 to obtain SBox and Cox, with the introduction of high number of carboxylic acid functions, 4.5 and 4.8 mmol/g, respectively. The adsorption kinetics of Co2+ and Cu2+ on SBox and Cox were modeled using two models (pseudo-first-order and pseudo-second-order) and the rate-limiting step controlling the adsorption was evaluated by Boyd and intraparticle diffusion models. The Sips and Langmuir models better fitted the isotherms with values of maximum adsorption capacity Qmax of 0.68 and 0.37 mmol/g for Co2+ and 1.20 and 0.57 mmol/g for Cu2+ adsorption on Cox and SBox, respectively. The reuse of both spent adsorbents was evaluated. Adsorption of Cu2+ and Co2+ on SBox in continuous was evaluated using a 22 factorial design with spatial time and initial metal concentration as independent variables and Qmax and effective use of the bed as responses. The breakthrough curves were very well described by the Bohart–Adams original model and the Qmax values for Co2+ and Cu2+ were 0.22 and 0.55 mmol/g. SBox confirmed to be a promising biomaterial for application on a large scale.

In the second part of this series of studies, the monocomponent adsorption of Cu2+, Co2+ and Ni2+ onto STA adsorbent in a fixed-bed column was investigated and optimized using a 2(2) central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed (Q(max)), efficiency of the adsorption process (EAP), and effective use of the bed (H). The higher Q(max) for Cu2+, Co2+ and Ni2+ were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart-Adams models. The changes in enthalpy (Delta H-ads degrees) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of Delta H-ads degrees were in the range of 3.0-6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption (E-des) and re-adsorption (Ere-ads) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of E-des and Ere-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale. (C) 2018 Elsevier Inc. All rights reserved.

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 (Qmax) 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.

Sugarcane bagasse cellulose succinate trimellitate (SBST) was prepared by a one-pot synthesis method. The synthesis of this novel mixed ester was investigated by a 2(3)-factorial design. The parameters investigated were time, temperature, and succinic anhydride mole fraction (chi(SA)). The responses evaluated were the adsorption capacity (q(co2+) and q(Ni2+)), weight gain (wg), and number of carboxylic acid groups (n(T center dot COOH)). C-1(3) Multiple Cross-Polarization solid-state NMR spectroscopy, H-1 NMR relaxometry, and Fourier-transform infrared spectroscopy were used to elucidate the SBST structure. The best SBST reaction conditions were 100 degrees C, 660 min, and chi(SA) of 0.2, which yielded SBST with a wg of 57.1%, n(T center dot COOH) of 4.48 mmol g (-1), and q(co2+) and q(Ni2+), of 0.900 and 0.963 mmol g(-1), respectively. The maximum adsorption capacities (Q(max)) (pH 5.75, 25 degrees C) estimated by the Redlich-Peterson model for Co2+ and Ni2+ were 1.16 and 1.29 mmol g(-1). The Delta H-ads degrees values for Co2+ and Ni2+ adsorption obtained by isothermal titration calorimetry were 8.03 and 6.94 kJ mol(-1). Regeneration and reuse of SBST were investigated and the best conditions applied for fixedbed column adsorption in five consecutive cycles. SBST was fully desorbed and Q(max) values for Co2+ (0.95 mmol g(-1)) and Ni2+ (1.02 mmol g(-1)) were estimated using the Bohart-Adams model. (C) 2019 Elsevier Inc. All rights reserved.

In the second part of this series of studies, the bicomponent adsorption of safranin-T (ST) and auramine-O (AO) on trimellitated sugarcane bagasse (STA) was evaluated using equimolar dye aqueous solutions at two pH values. Bicomponent batch adsorption was investigated as a function of contact time, solution pH and initial concentration of dyes. Bicomponent kinetic data were fitted by the pseudo-first-order and pseudo-second-order models and the competitive model of Corsel. Bicomponent equilibrium data were fitted by the real adsorbed solution theory model. The antagonistic interactions between ST and AO in the adsorption systems studied contributed to obtain values of maximum adsorption capacity in mono- (Qmax,mono) and bicomponent (Qmax,multi) lower than unity (Qmax,multi/Qmax,mono at pH 4.5 for ST of 0.75 and AO of 0.37 and at pH 7 for ST of 0.94 and AO of 0.43). Mono- and bicomponent adsorption of dyes in a fixed-bed column was evaluated at pH 4.5. The breakthrough curves were fitted by the Thomas and Bohart-Adams original models. Desorption of ST in a fixed-bed column was studied. The results obtained from the bicomponent batch and continuous adsorption showed that the presence of ST most affected the AO adsorption than the presence of AO affected the ST adsorption.

The preparation, characterisation and application of two pyridine-modified chitosan derivatives (C1 and C2) containing Cu(OAc)2 adsorbed as catalysts for the conversion of benzaldehyde into 2-nitro-1-phenylethanol are described. Quantitative solid-state 13C multiple-contact cross-polarization, magic-angle-spinning, nuclear magnetic resonance (MC-CP MAS NMR) measurements confirmed the successful grafting of 2-pyridinecarboxaldehyde and 6-methylpyridine-2-carboxaldehyde to the chitosan backbone and indicated that 47(±2)% of the NH2 groups were grafted for both C1 and C2. The use of C1-Cu(OAc)2 as a catalyst in the nitroaldol reaction led to 96(±1)% conversion and 19(±4)% enantiomeric excess (ee), while the use of C2-Cu(OAc)2 as a catalyst also promoted the nitroaldol reaction, affording almost quantitatively the expected 2-nitro-1-phenylethanol (98(±1)%) with 14.5(±1.5)% ee.

This study describes the use of succinylated twice-mercerized sugarcane bagasse containing adsorbed Cu2+ or Ni2+ ions from spiked aqueous solutions (2MSBA-Cu and 2MSBA-Ni) as heterogeneous catalysts for the catalytic oxidation of n-hexane and n-heptane in gas phase. To the best of our knowledge, this is the first study in which a spent adsorbent material based on lignocellulose biomass is used in the catalytic oxidation of volatile organic compounds. The adsorbent and spent adsorbent materials were characterized by FTIR, TGA and XRD. The amount of Cu2+ and Ni2+ adsorbed on 2MSBA was 0.49 and 2.49mmolg−1, respectively. The catalysts were active for total oxidation of n-hexane and n-heptane, even at low temperatures. 2MSBA-Cu exhibited higher catalytic activity than 2MSBA-Ni and surprisingly their performances were comparable or superior to those of some catalysts reported in the literature, including noble metal-based catalysts.

A solvent-free method for the one-step preparation of a new carboxylated-microcrystalline cellulose (MCCM) derivative is described in the present study. The method uses as esterification agent the 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid) and produced a novel material with high degree of functionalization. Optimized synthesis conditions yielded a MCCM with a weight gain of 79.9% and 4.21 mmol/g of carboxylic acid functions after 4 h of reaction using a microcrystalline cellulose (MCC) to Meldrum's acid (MA) ratio of 1:6. MCCM was characterized with success by FTIR, X-ray diffraction (XRD), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM).

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 bicomponent 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 LAST 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 (Delta H-ads) were obtained using isothermal titration calorimetry. The values of Delta H-ads 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. (C) 2017 Elsevier Inc. All rights reserved.

Cellulose (Cel) and sugarcane bagasse (SB) were oxidized with an H3PO4-NaNO2 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 4.8mmol/g and 4.5mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state 13C 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 (Qmax) of 1117.8mg/g of CV and 1223.3mg/g of AO on Cox and 1018.2mg/g of CV and 682.8mg/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.