Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by sugarcane bagasse and mercerized sugarcane bagasse chemically modified with succinic anhydride.

This work describes the preparation of new chelating material from mercerized sugarcane bagasse. The first part treats the chemical modification of non-mercerized sugarcane bagasse (SCB) and twice-mercerized sugarcane bagasse (MMSCB) with succinic anhydride. Mass percent gains (mpg) and degrees of succinylation (DS) of succinylated non- and twice-mercerized sugarcane bagasse 1 (SCB 1 and MMSCB 1) were calculated. MMSCB 1 exhibited an increase in mpg and DS of 49.2% and 0.9 mmol/g in relation to SCB 1. SCB 2 and MMSCB 2 were obtained by treatment of MMSCB 1 and SCB 1 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part evaluates and compares the adsorption capacity of SCB 2 and MMSCB 2 for Cu2+, Cd2+ and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. MMSCB 2 exhibited an increase in Qmax for Cd2+ (43.6 mg/g) and Pb2+ (83.3 mg/g) in relation to SCB 2

Fulereno[C60]: química e aplicações

Fullerene chemistry has become a very active research field in the two last decades, largely because of the exceptional properties of the C60 molecule and the variety of fullerene derivatives that appear to be possible. In this review, a general analysis of fullerene C60 reactivity is performed. The principal methods for the covalent modification of this fascinating carbon cage are presented. The prospects of using fullerene derivatives as medicinal drugs and photoactive materials in light converting devices are demonstrated

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse chemically modified with EDTA dianhydride (EDTAD).

This work describes the preparation of new chelating materials derived from cellulose and sugarcane bagasse for adsorption of Cu2+, Cd2+, and Pb2+ ions from aqueous solutions. The first part involved the mercerization treatment of cellulose and sugarcane bagasse with NaOH 5 mol/L. Non- and mercerized cellulose and sugarcane bagasse were then reacted with ethylenediaminetetraacetic dianhydride (EDTAD) in order to prepare different chelating materials. These materials were characterized by mass percent gain, X-ray diffraction, FTIR, and elemental analysis. The second part consisted of evaluating the adsorption capacity of these modified materials for Cu2+, Cd2+, and Pb2+ ions from aqueous single metal solutions, whose concentration was determined by atomic absorption spectroscopy. These materials showed maximum adsorption capacities for Cu2+, Cd2+, and Pb2+ ions ranging from 38.8 to 92.6 mg/g, 87.7 to 149.0 mg/g, and 192.0 to 333.0 mg/g, respectively. The modified mercerized materials showed larger maximum adsorption capacities than modified non-mercerized materials

An enantioselective synthesis of isoquinuclidines from 3-substituted chiral pyridinium salts.

A new enantioselective approach to chiral isoquinuclidines, such as 15, 18 and 21, is reported. The key step of these syntheses is a cycloaddition between chiral dihydropyridines 14 or 20, now readily available from tetrahydropyridinium salts 6 or 11, and achiral dienophiles. The reaction proceeds with a very good endo-selectivity and moderate d.e

An access to some functionalized azocine derivatives.

The syntheses, from readily accessible 3-alkyl-4-methoxy-1,3,4,5-tetrahydropyridine 1, of functionalized 1,6,7,8-tetrahydroazocine 7 and 1,2,7,8-tetrahydroazocine 9 are reported

A reação "click" na síntese de 1,2,3-triazóis: aspectos químicos e aplicações

The Copper-catalyzed azide-alkyne cycloaddition (CuAAC), often referred to as "click" reaction, has become a very popular reaction in the last years. It affords exclusively 1,4-disubstituted 1,2,3-triazoles and has been widely used to connect readily accessible building blocks containing various functional groups. The great success of this reaction is based on the fact that it is general, virtually quantitative and very robuste. The scope of this copper-catalyzed synthesis is extraordinary and the reaction has found numerous applications in many research fields, including biological chemistry and materials science. In this review, the main chemical aspects and applications of the "click" reaction in the synthesis of 1,2,3-triazoles are presented

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by cellulose and mercerized cellulose chemically modified with succinic anhydride.

This work describes the preparation of new chelating material from mercerized cellulose. The first part treats the chemical modification of non-mercerized cellulose (cell 1) and mercerized cellulose (cell 2) with succinic anhydride. Mass percent gains (mpg) and degree of succinylation (DS) of cell 3 (from cell 1) and cell 4 (from cell 2) were calculated. Cell 4 in relation to cell 3 exhibited an increase in mpg and in the concentration of carboxylic functions of 68.9% and 2.8 mmol/g, respectively. Cells 5 and 6 were obtained by treatment of cells 3 and 4 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part compares the adsorption capacity of cells 5 and 6 for Cu2+, Cd2+, and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. Cell 6 in relation to cell 5 exhibited an increase in Qmax for Cu2+ (30.4 mg/g), Cd2+ (86.0 mg/g) and Pb2+ (205.9 mg/g)

Obtaining a new carboxylated derivative of microcrystalline cellulose : an easy and solvent-free synthesis.

O presente trabalho descreve a prepara??o de um novo derivado carboxilado de celulose microcristalina, usando como agente de esterifica??o o ?cido de Meldrum (2,2-dimetil-1,3-dioxano-4,6-diona), sem utiliza??o de solvente. O m?todo produziu um novo material com alto grau de funcionaliza??o. Condi??es otimizadas de s?ntese produziram celulose microcristalina modificada com ?cido de Meldrum (MCCM) com um ganho de massa de 79,9 % e 4.21 mmol/g de fun??es carbox?licas introduzidas ap?s 4 horas de rea??o usando uma propor??o de celulose microcristalina (MCC) para ?cido de Meldrum (MA) de 1:6. MCCM foi caracterizada com sucesso usando FTIR, Difra??o de Raio-X (DRX), an?lise termogravim?trica (TG) e Microscopia Eletr?nica de Varredura (MEV).A solvent-free method for the one-step preparation of a new carboxylatedmicrocrystalline cellulose (MCCM) derivative is described in the present study. The method uses as esterification agent the 2,2-dimethyl-1,3-dioxane-4,6-dione ?Meldru??s a?id) and produced a novel material with high degree of functionalization. Optimized synthesis conditions yielded a MCCM with a weight gain of 79.9% and 4.21 mmol/g of carboxylic acid functions after 4 h of reaction using a microcrystalline cellulose (MCC) to Meldru??s a?id ?MA? ratio of ?:6. MCCM ?as ?hara?terized ?ith success by FTIR, X-ray diffraction (XRD), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM)

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