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

Modelagem e otimiza??o da adsor??o de metais t?xicos em coluna de leito-fixo utilizando baga?o de cana-de-a??car modificado quimicamente como adsorvente.

Programa de P?s-Gradua??o em Engenharia Ambiental. N?cleo de Pesquisas e P?s-Gradua??o em Recursos H?dricos, Universidade Federal de Ouro Preto.No presente trabalho avaliou-se a adsor??o de Cu 2+, Co 2+ e Ni2+, em sistema mono- e multicomponente, em uma coluna de leito fixo utilizando o baga?o de cana de a??car modificado quimicamente com anidrido trimel?tico (BAT) como adsorvente. O estudo foi feito de forma otimizada por meio da utiliza??o do planejamento experimental do tipo composto central, analisando as condi??es ?timas para as respostas (vari?veis dependentes): capacidade m?xima de adsor??o (Qmax), uso efetivo do leito (H) e efici?ncia do processo (EPads) na adsor??o de cada metal (adsor??o monocomponente). Tamb?m foi avaliado o efeito da presen?a de outros metais na capacidade de adsor??o do ?on met?lico de interesse na adsor??o em coluna de leito fixo (adsor??o multicomponente - Cu 2+, Co 2+ e Ni2+) por meio do planejamento experimental de mistura. Al?m disso, foi realizada a modelagem matem?tica das curvas de ruptura obtidas nos experimentos mono- e multicomponente e o estudo do efeito da composi??o de uma solu??o de processo sint?tica na capacidade de remo??o dos metais de interesse (Cu 2+, Co 2+ e Ni2+) pelo BAT. A reutiliza??o do BAT em ciclos de adsor??o/dessor??o consecutivos, o mecanismo de intera??o estabelecida entre os s?tios de adsor??o e os ?ons met?licos, al?m dos par?metros termodin?micos relacionados ao processo de adsor??o tamb?m foram determinados. Os resultados dos experimentos monocomponente mostraram que os efeitos da concentra??o (mmol/L) e do tempo espacial (min) interferem de forma semelhante na adsor??o dos ?ons de Cu2+, Co2+ e Ni2+ pelo BAT, obtendo menor ponto de ruptura (tb) para as condi??es de maior concentra??o e menor tempo espacial, e maior tb para a condi??o oposta em todos os ensaios de adsor??o. Por?m o Ni2+ ? adsorvido mais rapidamente, seguido do Co2+ e Cu2+, cujos tempos de exaust?o m?ximos, dentre os ensaios realizados, foram 250, 440 e 850 min para Ni2+, Co2+ e Cu2+, respectivamente. O Cu2+ obteve a maior Qmax (1,060 mmol/g) e o Co2+ a menor Qmax (0,800 mmol/g). As maiores EPads foram obtidas na adsor??o de Cu2+ e Co2+, com 76% em ambos e a maior H, de 2,50 cm, foi obtida na adsor??o de Cu2+ e Ni2+. Ambos os modelos, de Thomas e de Bohart-Adams, apresentaram bons ajustes aos dados experimentais em todos os ensaios, por?m devido aos elevados valores das constantes de Langmuir de cada metal, podese dizer que o modelo de Bohart-Adams representa melhor os sistemas estudados. Os resultados dos experimentos de mistura mostraram que o Cu2+ possui maior afinidade pelo BAT, sendo o Ni2+ e Co2+ substitu?dos por ele, causando o fen?meno de overshooting em suas curvas de ruptura. A ordem de afinidade foi Cu2+ > Ni2+ > Co2+, que est? de acordo com a s?rie de IrvingWilliams. A maior Qmax total foi de 1,088 mmol/g no experimento bicomponente Cu-Co, e a menor Qmax total, de 0,787 mmol/g, foi obtida no experimento bicomponente Co-Ni. Pelos modelamentos das curvas de ruptura dos experimentos de mistura foi poss?vel verificar que os mecanismos de convec??o predominaram (Pe >> 10) na maioria dos casos, por?m os metais apresentaram diferentes taxas de transfer?ncia de massa e etapas limitantes na adsor??o em coluna de leito fixo em cada caso, onde Bi apresentou um valor m?nimo de 3 e m?ximo de 100 e ? um m?nimo de 0,09 e m?ximo de 1,50. Estes resultados sugerem que ? necess?rio avaliar a adsor??o em sistemas din?micos antes de promover a aplica??o em larga escala ao se utilizar res?duos agroind?strias como bioadsorventes. O estudo com a solu??o sint?tica multicomponente mostrou que os ?ons Cu2+, Co2+ e Ni2+ s?o adsorvidos preferencialmente pelo BAT. O mecanismo de intera??o determinado foi de troca i?nica e os estudos termodin?micos mostraram que os sistemas de adsor??o s?o entropicamente dirigidos na condi??o padr?o.In the present study, the adsorption of Cu 2+, Co 2+, and Ni2+ was evaluated in a fixed-bed column in mono- and multi-component systems using sugarcane bagasse chemically modified with trimellitic anhydride (STA) as adsorbent. The monocomponent adsorption was optimized by means of central composite experimental designs, analyzing the optimal conditions for the responses (dependent variables): maximum adsorption capacity (Qmax), effective use of the bed (H) and process efficiency (EPads). It was also evaluated the effect of the presence of other metals in the adsorption capacity of a specific metal ion in a fixed-bed column adsorption (multicomponent adsorption - Cu 2+, Co 2+, and Ni2+) by means of a mixture experimental design. In addition, the mathematical modeling of the breakthrough curves obtained in the mono- and multi-component experiments was performed. The effect of a synthetic solution composition on the adsorption capacity of the metal ions, such as Cu 2+, Co 2+, and Ni2+ by STA was also evaluated. The reuse of STA in consecutive adsorption/desorption cycles, the type of interaction between the STA adsorption sites and the metal ions and the thermodynamic parameters related to the adsorption process were also determined. The obtained results for the monocomponent experiments showed that the effects of initial metal ion concentration (mmol/L) and spatial time (min) similarly interfered in the adsorption of Cu2+, Co2+ and Ni2+ ions onto STA, yielding a lower breaking point (tb) in conditions of higher initial metal ion concentration and shorter spatial time, and higher tb in the opposite condition for all adsorption experiments. However, Ni2+ is adsorbed faster, followed by Co2+ and Cu2+, whose maximum exhaustion times were 250, 440 and 850 min for Ni2+, Co2+ and Cu2+, respectively. The Cu2+ ions had the highest Qmax (1.060 mmol/g) and Co2+ the lowest Qmax (0.800 mmol/g). The highest EPads were obtained in the adsorption of Cu2+ and Co2+, with 76% for both and the highest H (2.50 cm) was obtained in the adsorption of Cu2+ and Ni2+. Both Thomas and Bohart-Adams models presented a good fit to the experimental data for all breakthrough curves; however, due to the high values of the Langmuir constants for each metal, it can be concluded that the Bohart-Adams model represents better the adsorption systems studied. The results of the mixture experiments showed that Cu2+ had a higher affinity for STA, where Ni2+ and Co2+ being substituted for it, causing the phenomenon of overshooting in their breakthrough curves. The order of affinity was Cu2+ > Ni2+ > Co2+, which is in good agreement with the Irving-Williams series. The highest total Qmax was 1.088 mmol/g for the Co-Cu bicomponent experiment, and the lowest total Qmax, 0.787 mmol/g, was obtained for the Co-Ni bicomponent experiment. The modeling of the breakthrough curves in the mixture experiments allowed to conclude that the convection mechanisms predominated (Pe >> 10) in most cases; however, the metals exhibited different mass transfer rates and rate-limiting steps in fixed-bed column adsorption experiments, where Bi had a minimum value of 3 and maximum of 100 and ? a minimum of 0.09 and a maximum of 1.50. These results suggest that it is necessary to evaluate the adsorption in dynamic systems before promoting the application in large scale when agroindustrial residues are used as bioadsorbents. The study with the multicomponent synthetic solution showed that the Cu2+, Co2+ and Ni2+ ions are preferentially adsorbed by STA. The interaction mechanism determined was ion exchange and the thermodynamic studies showed that the system is entropically driven under standard condition

Trimellitated sugarcane bagasse : a versatile adsorbent for removal of cationic dyes from aqueous solution. Part II: batch and continuous adsorption in a bicomponent system.

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

Modeling adsorption of copper(II), cobalt(II) and nickel(II) metal ions from aqueous solution onto a new carboxylated sugarcane bagasse. Part II : Optimization of monocomponent fixed-bed column adsorption.

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 22 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 (Qmax), efficiency of the adsorption process (EAP), and effective use of the bed (H). The higher Qmax 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 (DadsH ) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of DadsH were in the range of 3.0?6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption (Edes) and readsorption (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 Edes and Ere-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale

Synthesis and application of sugarcane bagasse cellulose mixed esters. Part II : removal of Co2+ and Ni2+ from single spiked aqueous solutions in batch and continuous mode.

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 23-factorial design. The parameters investigated were time, temperature, and succinic anhydride mole fraction (?SA). The responses evaluated were the adsorption capacity (qCo2+ and qNi2+), weight gain (wg), and number of carboxylic acid groups (nT,COOH). 13C Multiple Cross-Polarization solid-state NMR spectroscopy, 1H NMR relaxometry, and Fourier-transform infrared spectroscopy were used to elucidate the SBST structure. The best SBST reaction conditions were 100??C, 660?min, and ?SA of 0.2, which yielded SBST with a wg of 57.1%, nT,COOH of 4.48?mmol?g?1, and qCo2+ and qNi2+ of 0.900 and 0.963?mmol?g?1, respectively. The maximum adsorption capacities (Qmax) (pH 5.75, 25??C) estimated by the Redlich-Peterson model for Co2+ and Ni2+ were 1.16 and 1.29?mmol?g?1. The ?adsH? 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 fixed-bed column adsorption in five consecutive cycles. SBST was fully desorbed and Qmax values for Co2+ (0.95?mmol?g?1) and Ni2+ (1.02?mmol?g?1) were estimated using the Bohart-Adams model