Optimization of cellulose and sugarcane bagasse oxidation : application for adsorptive removal of crystal violet and auramine-O from aqueous solution.

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 4.8 mmol/g and 4.5 mmol/g of carboxylic acid groups, respectively. Cox and SBox were characterized by FTIR, TGA, PZC and solid-state 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-secondorder kinetic model. Adsorption isotherms were well fitted by the Langmuir and Konda models, with maximum adsorption capacities (Qmax) 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

Oxidized renewable materials for the removal of cobalt(II) and copper(II) from aqueous solution using in batch and fixed-bed column adsorption.

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 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 and effective use of the bed as responses. The breakthrough curves were very well described by the Bohart?Adams original model and the 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

Modifica??o de materiais lignocelul?sicos atrav?s de rea??es de oxida??o para adsorver c?tions met?licos em solu??o aquosa.

Programa de P?s-Gradua??o em Qu?mica. Departamento de Qu?mica, Instituto de Ci?ncias Exatas e Biol?gicas, Universidade Federal de Ouro Preto.A contamina??o de corpos d??gua por efluentes industriais ? um crescente problema ambiental, principalmente quando causada por metais pesados, que s?o t?xicos, n?o biodegrad?veis e bioacumulativos por meio da cadeia alimentar, causando v?rias doen?as. Dessa forma, a remo??o destes poluentes dos efluentes industriais se mostra uma preocupa??o importante. A bioadsor??o ? um processo de tratamento de ?guas residuais que tem atra?do consider?vel interesse na remo??o deste tipo de contaminante. Neste contexto, o presente trabalho de disserta??o visou preparar novos materiais adsorventes para a remo??o de ?ons met?licos em solu??o aquosa. Foram preparados um adsorvente, a partir da celulose, e outro, a partir do baga?o de cana-de-a??car, para serem utilizados na remo??o, em regime de batelada, dos metais t?xicos cobre e cobalto em solu??es aquosas, idealmente contaminadas. Por meio de rea??o de oxida??o (NaNO2 / H3PO4), foram introduzidas fun??es ?cido carbox?lico nas estruturas da celulose (C) e do baga?o de-cana-de a??car (B1), originando os materiais celulose oxidada (COX) e baga?o de cana - de - a??car oxidado (BOX1), respectivamente. A oxida??o dos materiais foi investigada, considerando o efeito da quantidade de NaNO2 e H3PO4 e do tempo de rea??o atrav?s da an?lise da porcentagem de ganho de massa (pgm) e perda de massa (ppm) e do n?mero de fun??es ?cidas (nCOOH) introduzidas. As modifica??es na celulose e no baga?o de cana - de - a??car foram avaliadas pelas t?cnicas de FTIR, TGA e PCZ. O estudos de adsor??o em batelada foram realizados empregando os metais cobalto(II) e cobre(II). O pH considerado ?timo para os estudos de adsor??o foi de 5,5, tanto para o Cu2+ quanto para o Co2+. Para a adsor??o de Cu2+ nos dois materiais, o modelo cin?tico que melhor se ajustou aos dados experimentais foi o modelo de pseudo segunda ordem e para o ?on Co2+ foi o modelo de pseudo primeira ordem. Foram utilizados os modelos de isoterma de Langmuir, Freundlich e Sips. O COX apresentou capacidade de adsor??o m?xima (Qm?x) de 74,36 e 41,24 mg/g, para Cu2+ e Co2+, respectivamente, e o BOX1 apresentou Qm?x de 38,07 e 23,64 mg/g para Cu2+ e Co2+, respectivamente. Os estudos de dessor??o e readsor??o mostraram a potencialidade de reutiliza??o do adsorvente. O par?metro termodin?mico de adsor??o foi determinado a partir da energia livre padr?o ?adsG?, utilizado para discutir o mecanismo de adsor??o dos metais em COX e BOX1.Contamination of water bodies by industrial effluents is a growing environmental problem, when caused by heavy metals, since these metals are toxic, non-biodegradable, and bioaccumulative through the food chain, causing various diseases. So, the removal of these pollutants from industrial effluents is shown a major concern. Adsorption is a process of treating wastewater that has attracted considerable interest in the removal of such contaminant. In this context, this dissertation aimed to prepare new adsorbent materials for removal of metal ions in aqueous solution. An adsorbent were prepared from the cellulose, and other, from sugar-cane bagasse, for use in removing, in a batch system, the toxic metals copper and cobalt in aqueous solutions, ideally contaminated. Through oxidation reaction (NaNO2 / H3PO4), carboxylic acid functions were introduced into the cellulose structure (C) and the sugar-cane bagasse (B1), yielding COX and BOX1 materials, respectively. The oxidation of the materials was investigated, considering the effect of the amount of NaNO2 and H3PO4, and the reaction time by analyzing the percentage of weight gain (pwg) and loss of weight (plw) and the number of acid functions (nCOOH) introduced. Changes in cellulose and sugar-cane bagasse were evaluated by FTIR techniques, TGA and PCZ. The batch adsorption studies were conducted employing the cobalt metal (II) and copper (II). The pH considered optimal for the adsorption studies was 5.5 for both Cu2+ and Co2+. For the adsorption of Cu2+ in the two materials, the kinetic model that best fit the experimental data was the model of pseudo second order and the Co2+ ion is the pseudo first order model. The Langmuir isotherm model, Freundlich and Sips were used. COX showed maximum adsorption capacity (Qmax) of 74.36 and 41.24 mg / g, Cu2+ and Co2+, respectively, and BOX1 presented Qmax of 38.07 and 23.64 mg / g for Cu2+ and Co2+, respectively. The adsorption and desorption studies showed the potential reuse of the COX adsorbent. The thermodynamic parameters of adsorption was determined from the standard free energy ?adsG?, used to discuss the metal adsorption mechanism in COX and BOX1

Oxidized Renewable Materials for the Removal of Cobalt(II) and Copper(II) from Aqueous Solution Using in Batch and Fixed-Bed Column Adsorption

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