Adsorção de metais e corantes em celulose modificada com anidrido trimelítico.

Programa de Pós-Graduação em Engenharia Ambiental. Núcleo de Pesquisas e Pós-Graduação em Recursos Hídricos, Pró-Reitoria de Pesquisa e Pós Graduação, Universidade Federal de Ouro Preto.A contaminação de corpos d’água por efluentes industriais é um problema ambiental crescente que necessita de atenção, não só frente à crise hídrica vivida pelo país, mas também, pela preservação deste bem para as próximas gerações. Dois poluentes importantes presentes nestes efluentes são os metais pesados e os corantes têxteis. Estes poluentes são tóxicos para várias formas de vida e não biodegradáveis, tendem a acumular-se em organismos causando várias doenças e desordens. Dessa forma a remoção destes poluentes dos efluentes industriais se mostra uma preocupação importante. A bioadsorção é um processo de tratamento de águas residuais que tem atraído considerável interesse recentemente na remoção deste tipo de contaminante. Neste trabalho foi preparado um adsorvente a partir da celulose para ser utilizado na remoção de metais tóxicos e corantes de soluções idealmente contaminadas em batelada. A celulose foi modificada quimicamente utilizando o anidrido trimelítico (AT), produzindo um material contendo funções ácido carboxílico em sua estrutura (CAT). A esterificação da celulose (C) foi investigada e otimizada considerando o efeito da quantidade de AT e o tempo de reação além da análise da porcentagem de ganho de massa (pgm) e do número de funções ácidas (nCOOH) introduzidas. As modificações na celulose foram avaliadas pelas técnicas de FTIR, TGA, RMN 13C, PCZ, MEV e análise elementar de C, H e N. Estudos de adsorção em batelada foram realizados empregando os metais cobalto (II), cobre(II) e níquel(II) e os corantes safranina-T e auramina-O. A CAT apresentou capacidade de adsorção máxima (Qmáx) de 0,960, 1,487 e 1,014 mmol.g-1 para Co+2, Cu+2 e Ni+2 e 3,743 e 5,175 mmol.g-1 para safranina-T e auramina-O, respectivamente. Foram avaliados a influência da dosagem de adsorvente, do pH, do tempo de contato e da concentração inicial de adsorvato. Para tentar descrever os sistemas de adsorção foram utilizados os modelos de isoterma de Langmuir, Freundlich, Sips, Redlich- Peterson, Hill-de Boer, Fowler-Guggenheim, um modelo para multicamadas e os modelos cinéticos de pseudo primeira e pseudo segunda ordem. Estudos de dessorção e re-adsorção mostraram a potencialidade de reutilização do adsorvente CAT. Os parâmetros termodinâmicos de adsorção ΔadsH° e ΔadsS° foram determinados com o auxílio da calorimetria de titulação isotérmica (ITC) que juntamente com a energia livre padrão ΔadsG° foram utilizados para discutir o mecanismo de adsorção de metais em CAT.Contamination of water bodies by industrial wastewaters is a growing environmental problem that needs attention, not only for the water crisis faced by the country but also for the preservation of this asset for future generations. Two major pollutants present in these effluents are heavy metals and textile dyes. These pollutants are toxic to many living organisms and not biodegradable, tend to accumulate in organisms causing various diseases and disorders. Thus, the removal of these pollutants from industrial effluents is a major concern. The biosorption is a wastewater treatment method that has attracted substantial interest recently for the removal of such contaminants. An adsorbent was prepared from the cellulose to be used for the removal of toxic metals and dyes from spiked aqueous solutions in batch mode. The cellulose was chemically modified with trimellitic anhydride (TA), yielding a material containing carboxylic acid functions (CAT). The esterification of cellulose (C) was investigated and optimized as a function of AT concentration and reaction time by analyzing the percentage weight gain (pwg) and the amount of acid groups (nCOOH) introduced. Modified cellulose was characterized by FTIR, TGA, 13C NMR, PCZ, SEM and elemental analysis of C, H and N. Batch adsorption studies were performed using salts of copper (II), cobalt (II) and nickel (II) and dyes safranin- T and auramine-O. CAT showed maximum adsorption capacity (Qmax) of 0.960, 1.487 and 1.014 mmol.g-1 for Co+2, Cu+2 and Ni+2 and 3,743 and 5,175 mmol.g-1 for safranin-T and auramine-O, respectively. The influence of the adsorbent dosage, pH, contact time and initial adsorbate concentration on adsorption was evaluated. To describe the adsorption systems isotherms models of Langmuir, Freundlich, Sips, Redlich-Peterson, Hill-de Boer, Fowler- Guggenheim, multilayer model and kinetic models of pseudo-first and pseudo-second order were used. Desorption and readsorption studies showed that the potential reuse of the adsorbent CAT is feasible. Changes in enthalpy (ΔadsH°) and entropy (ΔadsS°) were determined using isothermal titration calorimetry (ITC) technique. These parameters together with changes in free energy (ΔadsG°) were used to discuss the mechanism of metal ions adsorption on CAT

Removal of cobalt (II), copper (II), and nickel (II) ions from aqueoussolutions using phthalate - functionalized sugarcane bagasse : mono - and multicomponent adsorption in batch mode.

This study describes, in detail, the chemical modification of sugarcane bagasse with phthalic anhydrideto produce a carboxylate-functionalized sugarcane bagasse (SPA). The optimized modification condi-tions yielded SPA with a percent weight gain of 77.08% and an amount of carboxylic acid groups of 4.76mmol/g. The SPA was characterized by PZC, FTIR, elemental analysis, TGA, and SEM-EDX. An SPA adsor-bent was used to remove Co2+, Cu2+, and Ni2+from aqueous solution in mono- and multicomponentsystems in batch mode. The adsorption kinetics followed a pseudo-second-order model. The adsorptionrate constants assumed the following order: k2,Co2+> k2,Ni2+> k2,Cu2+. Four mono- and multicomponentisotherm models were used to model the adsorption data. Monocomponent data were well described bythe Langmuir model, whereas bicomponent data were well described by the modified extended Lang-muir and P-Factor models. The maximum adsorption capacities (Qmax,mono) for the Langmuir model were0.561, 0.935, and 0.932 mmol/g for Co2+, Cu2+, and Ni2+, respectively. Adsorption in bicomponent systemsrevealed that Cu2+suppressed the adsorption of Co2+and Ni2+, whereas Ni2+suppressed the adsorptionof Co2+. Desorption studies revealed that the SPA adsorbent could be fully desorbed with a 1 mol/L HNO3solution

Application of a new carboxylate-functionalized sugarcane bagasse for adsorptive removal of crystal violet from aqueous solution : kinetic, equilibrium and thermodynamic studies.

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

Application of Raw and Chemically Modified Biomasses for Heterogeneous Cu-Catalysed Conversion of Aryl boronic Acids to Phenols Derivatives

International audienceThis 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-6aminoethyleneamino 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 using13C 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

Trimellitated sugarcane bagasse: A versatile adsorbent for removal of cationic dyes from aqueous solution. Part I: Batch adsorption in a monocomponent system

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

Differential alterations in mitochondrial function induced by a choline-deficient diet: Understanding fatty liver disease progression

http://www.sciencedirect.com/science/article/B6W8G-4T72WXD-1/2/734055ec11eadc8100fee13e06c683d

Indirubin-3'-oxime impairs mitochondrial oxidative phosphorylation and prevents mitochondrial permeability transition induction

http://www.sciencedirect.com/science/article/B6WXH-4T7085D-2/2/535e45a8cc0ac06fe24206561a5ee79

Regular article synthesis and application of a new carboxylated cellulose derivative. Part I: Removal of Co 2+ , Cu 2+ and Ni 2+ from monocomponent spiked aqueous solution

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 (nCOOH), elemental analysis, FTIR, TGA, solid-state ^13C NMR, X-ray diffraction (DRX), specific surface area, pore size distribution, SEM and EDX. The best CTA synthesis condition yielded a pwg and nCOOH 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 ΔadsH° 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

Modeling mono- and multi-component adsorption of cobalt(II), copper(II), and nickel(II) metal ions from aqueous solution onto a new carboxylated sugarcane bagasse. Part I: Batch adsorption study.

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 pseudosecond- order model. The adsorption rate constant showed the following order: k2,Ni 2+ > k2,Cu 2+ > k2,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 (Qmax,mono) obtained from the Langmuir model were 1.140, 1.197, and 1.563 mmol/g for Co2+, Cu2+, and Ni2+, respectively. The competitive studies demonstrated that the multicomponent adsorption capacity (Qmax,multi) was smaller than Qmax,mono, as a result of the interaction between the metal ions. Desorption studies showed that all metal ions could be fully desorbed from STA

Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution

International audienceThe 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 C1 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 re-adsorption. 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