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

S?ntese de um derivado bifuncionalizado in?dito de quitosana para a remo??o dos ?ons met?licos Cu2+ e CrO4 2- em solu??o aquosa.

Programa de P?s-Gradua??o em Engenharia de Materiais. Departamento de Engenharia Metal?rgica, Escola de Minas, Universidade Federal de Ouro Preto.A contamina??o da ?gua tem atra?do preocupa??o internacional nos ?ltimos anos. Essa contamina??o acontece por diferentes poluentes e nesse grupo de poluentes se encontram os metais pesados presentes em concentra??es t?xicas nos sistemas aquosos. Por isso ? importante procurar formas de tratar esses corpos d??gua contaminados, e dentre as op??es, se encontra o uso de biossorventes como a quitosana, biopol?mero de f?cil acesso e que pode ser modificada para aumentar sua capacidade de adsor??o. Nesse projeto a quitosana foi usada na prepara??o de um novo material bifuncionalizado. Essas modifica??es foram realizadas com o intuito de produzir um material capaz de remover c?tions e oxi?nions de metais pesados. Para essa modifica??o reagiu-se a quitosana com 2-piridinacarboxialde?do de modo a obter uma fun??o capaz de quelar c?tions met?licos em valores de pH b?sicos e em valores de pH ?cidos atrair oxi?nions por atra??o eletrost?tica. Introduziu-se tamb?m fun??es carboxilato atrav?s de rea??o com dianidrido de EDTA possibilitando adsorver c?tions met?licos quando o material se encontra desprotonado, gerando o adsorvente Q4. Para a rea??o com dianidrido de EDTA foi realizado um planejamento estat?stico 2?, com repeti??o do ponto central a fim de encontrar a melhor condi??o reacional dentre os par?metros avaliados. As vari?veis analisadas foram tempo reacional, equivalente em massa de dianidrido de EDTA e temperatura e a resposta de interesse foi massa final obtida. O material adsorvente in?dito bifuncionalizado Q4 foi caracterizado por FTIR, TGA, 13C RMN, an?lise elementar e MEV e foi tamb?m avaliado quanto ? sua capacidade de adsor??o em fun??o do pH, do tempo de contato (cin?tica) e da concentra??o inicial dos metais (isoterma). As capacidades m?ximas de adsor??o (Qmax) de Q4 para Cu2+ e Cr6+ foram de 2,33mmol/g e 3,66mmol/g, respectivamente. A capacidade de readsor??o do adsorvente Q4 regenerado tamb?m foi avaliada (2,20 mmol/g para Cu2+ e 1,54 mmol/g para Cr6+).The water contamination has attracted international concern in recent years. This contamination occurs by different pollutants and in this group of pollutants are found the heavy metals present in toxic concentrations in the aqueous system. Therefore it is important to look for ways to treat these contaminated water bodies and among the options, we find the use of biosorbents such as chitosan, biopolymer easily accessible that can be modified to increase its adsorption capacity. In this work chitosan was used in the preparation of a new bifunctional material. These modifications were carried out in order to produce a material capable of removing cations and oxyanions from heavy metals. For this modification the biopolymer was reacted with 2-pyridinecarboxyaldehyde to obtain a function capable of chelating metal cations at basic pH values and acidic pH values to attract oxyanions by electrostatic attraction. Carboxylate functions were also introduced by reaction with EDTA dianhydride enabling adsorption of metal cations when the material is deprotonated, obtaining Q4 adsorbent. For the reaction with dianhydride of EDTA, statistical analysis 2? was performed, with repetition of the central point in order to find the best reaction condition among the evaluated parameters. The analyzed variables were reaction time, EDTA dianhydride equivalent mass and temperature and the response of interest was the final mass obtained. The adsorbent material Q4 was characterized by FTIR, TGA, 13C NMR, elemental analysis and SEM and was evaluated for adsorption capacity as a function of pH, contact time (kinetics) and initial metal concentration (isotherm). The maximum adsorption capacities (Qmax) of Q4 for Cu2+ and Cr6+ were 2,33 mmol/g and 3,66 mmol/g, respectively. The readsorption capacity of the regenerated Q4 adsorbent was also evaluated (2,20mmol/g for Cu2+ and 1,54mmol/g for Cr6+)

Bifunctionalized chitosan : a versatile adsorbent for removal of Cu(II) and Cr(VI) from aqueous solution.

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