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

S?ntese de materiais lignocelul?sicos oxidados e bifuncionalizado para a remo??o de corantes cati?nicos e ani?nico 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.Este trabalho descreve a prepara??o de adsorventes lignocelul?sicos para a adsor??o de corantes cati?nicos e ani?nico em solu??o aquosa. A primeira parte relata a otimiza??o da oxida??o da celulose (Cel) e do baga?o de cana de a??car (BCA) pelo sistema NaNO2/H3PO4 e a aplica??o dos produtos oxidados na adsor??o dos corantes cati?nicos violeta cristal (VC) e auramina-O (AO). As condi??es de oxida??o foram otimizadas por m?todos estat?sticos de planejamento experimental e superf?cie de resposta. A oxida??o otimizada introduziu 4,8 mmol/g e 4,5 mmol/g de fun??es ?cido carbox?lico na Cel e no BCA respectivamente. Os adsorventes celulose oxidada (Cox) e Baga?o de cana de a??car oxidado (Box) foram avaliados quanto a capacidade de adsor??o em fun??o do pH, do tempo de contato (cin?tica) e da concentra??o inicial dos corantes (isoterma). O modelo cin?tico que melhor se ajustou para a adsor??o de VC por Cox foi o de Elovich (EE) e para a adsor??o de AO por Cox foi o de pseudo primeira ordem (PPO). Para a adsor??o de VC e AO por Box o modelo cin?tico que melhor se ajustou foi o de pseudo segunda ordem(PSO). A avalia??o do modelo cin?tico difus?o intrapart?cula (DIP) indicou que a difus?o de VC e AO nos poros da Cox e do Box n?o pode ser considerada a ?nica etapa relevante para a cin?tica de adsor??o nestes sistemas. Os estudos das isotermas de adsor??o apontaram Langmuir como o melhor modelo para a descri??o da adsor??o de VC por ambos os adsorventes e Konda como o melhor modelo para descrever a adsor??o de AO pelos dois adsorventes. As capacidades de adsor??o estimadas pelo modelo de Langmuir foram de 1117,8 mg/g e 1018,2 mg/g de VC em Cox e Box respectivamente. As capacidades de adsor??o estimadas pelo modelo de Konda foram de 1223,3 mg/g e 628,8 mg/g de AO em Cox e Box respectivamente. Os estudos de dessor??o e readsor??o mostraram ser poss?vel o reuso da Cox e do Box. A segunda parte deste trabalho descreve a produ??o, a partir da celulose, do adsorvente bifuncionalizado com caracter?sticas zwitteri?nicas, CM3, para a adsor??o em sistema monocomponente do corante cati?nico violeta cristal e do corante ani?nico alaranjado II (AII). A modifica??o qu?mica da celulose ocorreu por meio de succinila??o com anidrido succ?nico e posterior modifica??o com cloreto de colina. O modelo cin?tico que melhor se ajustou ? adsor??o de ambos os corantes por CM3 foi o de pseudo segunda ordem. A avalia??o do modelo DIP indicou que a difus?o de VC ou AII nos poros da CM3 n?o pode ser considerada como a ?nica etapa relevante para a cin?tica de adsor??o nestes sistemas. Os estudos das isotermas de adsor??o apontaram Konda e Langmuir como os melhores modelos para descrever a adsor??o de VC e AII por CM3, respectivamente. A capacidade de adsor??o do corante cati?nico VC por CM3 foi de 2367,5 mg/g e do corante ani?nico AII foi de 217,5 mg/g.This work describes the preparation of lignocellulosic adsorbents derived from cellulose (Cel) and sugarcane bagasse (SB) for adsorption of cationic and anionic dyes in aqueous solution. The first part describes the optimization of cellulose and sugarcane bagasse oxidation using NaNO2/H3PO4 system, and the use of oxidized products in the adsorption of cationic dyes crystal violet (VC) and auramine-O (AO). 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. 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. The intraparticle diffusion kinetic model (IPD) indicated that the diffusion of VC and AO in the Cox and Box pores cannot be the only relevant step for adsorption kinetics in these systems. 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. The second part describes the chemical modification of Cellulose using Succinic anhydride and choline chloride as modifying agent to introduce carboxylic and ammonium functional groups on the cellulose. The produced adsorbent (CM3) is a zwitterionic material, and was used for adsorption of the cationic CV and anionic orange II (AII) dyes in a single component aqueous system. The adsorption of CV and AII on CM3 was described by the pseudo-second-order kinetic model. The IPD model indicated that diffusion of VC or AII in the CM3 pores cannot be the only relevant step for adsorption kinetics in these systems. Adsorption isotherms were well fitted by the Konda and Langmuir model for CV and AII respectively, with maximum adsorption capacities (Qmax) of 2367.5 mg/g of CV and 217.5 mg/g of AII on CM3

Imobilização do mediador redox riboflavina em fibra de celulose para degradação anaeróbica do azo corante amarelo ouro remazol RNL.

Programa de Pós-Graduação em Engenharia Ambiental. PROÁGUA, Pró-Reitoria de Pesquisa e Pós Graduação, Universidade Federal de Ouro Preto.A literatura tem demonstrado a eficiência de algumas substâncias na melhoria da cinética de remoção de cor em águas residuárias contendo corantes do tipo azo. Entre essas substâncias está a riboflavina (vitamina B2) que é conhecida por atuar como mediador redox nas transferências de elétrons de uma fonte doadora para o azo corante. A riboflavina em sua forma livre é solúvel em meio aquoso e pode ser perdida no efluente final em um sistema de tratamento. A imobilização desta vitamina em um suporte insolúvel pode proporcionar a retenção e recuperação da mesma nos reatores e consequentemente viabilizar o seu reuso diminuindo os custos do processo. Neste trabalho realizou-se a síntese de um novo material (CM3) contendo riboflavina imobilizada na celulose via ligação covalente e investigou-se a sua influência na degradação anaeróbia do azo corante amarelo ouro remazol RNL. Os ensaios foram feitos em escala de bancada e regime de batelada por períodos de 48 horas e temperatura controlada (25°C). A primeira etapa do trabalho consistiu na modificação química da celulose. Este polímero foi mercerizado, succinilado e passou por reação com anidrido acético para em seguida reagir com a riboflavina e dar origem à CM3. Os efeitos da modificação foram analisados por técnicas de infravermelho e análise elementar. A concentração de riboflavina introduzida na celulose foi estimada em 71,3mg/g. A estabilidade deste material foi testada em diferentes condições de pH e mostrou-se estável entre os pH 2 e 9. A segunda etapa do trabalho teve como objetivo avaliar os efeitos da riboflavina imobilizada na degradação anaeróbia do azo corante amarelo ouro remazol RNL. Os experimentos realizados com lodo anaeróbio e CM3 mostraram uma taxa de remoção 1,56 vezes maior do que os ensaios feitos sem nenhum tipo de mediador redox, comprovando assim a efetividade deste material na melhoria da cinética de degradação anaeróbia do azo corante modelo.Reports in the literature have demonstrated the effectiveness of some substances in improving the kinetics of color removal in wastewater containing azo dyes. Among these substances is riboflavin (vitamin B2), which is known to act as a redox mediator in the transfer of electrons from a donor source such as glucose to an azo dye. The use of riboflavin in its free form, which is soluble in aqueous medium, is not attractive from an economic point of view since it is lost in the effluent upon treatment. Immobilization of this vitamin onto an insoluble support may provide improvements such as retention and recovery in the same reactor and allowing its reuse thereby reducing the costs related to the process. The aim of this work was to synthesize a new material (CM3) containing riboflavin immobilized covalently onto cellulose and investigate its influence on the anaerobic degradation of a model azo dye (Remazol Gold Yellow RNL). The tests were performed in batch reactors and the temperature of the system was set at 25° C and maintained for 48 h. The first stage of the study was the chemical modification of cellulose. For this, the homopolymer was mercerized (NaOH 20%), modified with succinic anhydride, and then reacted with acetic anhydride in order to form internal carboxylic acid anhydride functions which were used to bind riboflavin to cellulose, yielding CM3. Chemical modification of cellulose was evaluated by techniques as IR with Fourier transform and elemental analysis. The concentration of riboflavin introduced into the cellulose was estimated an 71.3mg/gCM3 and chemical stability tests with CM3 showed it was stable between pH 2 and 9. The second stage of the study was to evaluate the effects of riboflavin immobilized on to cellulose (CM3) on the anaerobic degradation of azo dye, Remazol Gold Yellow (RNL). The experiments with anaerobic sludge and CM3 showed a removal rate 1.65 times greater than those tests carried out without any redox mediator, thereby evidencing the effectiveness of the immobilized catalyst

Application of cellulose-immobilized riboflavin as a redox mediator for anaerobic degradation of a model azo dye Remazol Golden Yellow RNL.

This study described the anaerobic degradation of the azo dye Remazol Golden Yellow RNL (RGY-RNL) using cellulose-immobilized riboflavin (MC 3) as the redox mediator. This new solid support containing immobilized riboflavin was synthesized from succinylated mercerized cellulose, and was characterized by elemental analysis, FTIR, and solid-state 13C NMR. MC 3 was resistant to pH 2–9, and anaerobic degradation of RGY-RNL using MC 3 in the presence of anaerobic sludge yielded a zero order degradation rate constant (k0,obs) equal to 0.189 mg/L h, which was 56% better than experiments carried out without a redox mediator. Color removal efficiency after 48 h of degradation averaged 89.4% in experiments with MC 3 and 72% without the addition of a redox mediator. These results showed that MC 3 can be used to immobilize redox mediators, allowing reduction of wastewater treatment cost

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