Removal of Pb(II) ions and malachite green dye from wastewater by activated carbon produced from lemon peel

In the present study, a high-surface area activated carbon was prepared by chemical activation of lemon peel with H3PO4 as the active agent. Then, the adsorption behavior of Malachite green dye and Pb(II) ions on the produced activated carbon was studied. Batch process was employed for sorption kinetics and equilibrium studies. Experimental data were fitted to various isotherm models. According to the Langmuir model, the maximum adsorption capacities of Malachite green dye and Pb(II) ions were found to be 66.67 and 90.91 mg g-1, respectively, at room temperature. Kinetic studies showed the adsorption process followed a pseudo second-order rate model. The sorption kinetics were controlled by intra-particle diffusion. The results indicated that the produced activated carbon can be economically and effectively used as an adsorbent for the removal of Malachite green dye and Pb(II) ions from wastewaters.

METHANE DRY REFORMING OVER Ni SUPPORTED ON PINE SAWDUST ACTIVATED CARBON: EFFECTS OF SUPPORT SURFACE PROPERTIES AND METAL LOADING

The influence of metal loading and support surface functional groups (SFG) on methane dry reforming (MDR) over Ni catalysts supported on pine-sawdust derived activated carbon were studied. Using pine sawdust as the catalyst support precursor, the smallest variety and lowest concentration of SFG led to best Ni dispersion and highest catalytic activity, which increased with Ni loading up to 3 Ni atoms nm-2. At higher Ni loading, the formation of large metal aggregates was observed, consistent with a lower "apparen" surface area and a decrease in catalytic activity. The H2/CO ratio rose with increasing reaction temperature, indicating that increasingly important side reactions were taking place in addition to MDR.

Immersion enthalpy variation of surface-modified mineral activated carbon in lead (II) aqueous solution adsorption: the relation between immersion enthalpy and adsorption capacity

An activated carbon was obtained by chemical activation with phosphoric acid, CM, from a mineral carbon. Afterwards, the carbon was modified with 2 and 5 molL-1, CMox2 and CMox5 nitric acid solutions to increase the surface acid group contents. Immersion enthalpy at pH 4 values and Pb2+ adsorption isotherms were determined by immersing activated carbons in aqueous solution. The surface area values of the adsorbents and total pore volume were approximately 560 m².g-1 and 0.36 cm³g-1, respectively. As regards chemical characteristics, activated carbons had higher acid sites content, 0.92-2.42 meq g-1, than basic sites, 0.63-0.12 meq g-1. pH values were between 7.4 and 4.5 at the point of zero charge, pH PZC. The adsorbed quantity of Pb2+ and the immersion enthalpy in solution of different pH values for CM activated carbon showed that the values are the highest for pH 4, 15.7 mgg-1 and 27.6 Jg-1 respectively. Pb2+ adsorption isotherms and immersion enthalpy were determined for modified activated carbons and the highest values were obtained for the activated carbon that showed the highest content of total acid sites on the surface.

Design of an adsorbent employing activated carbon fiber to remove lead

Zorflex® activated carbon fibers (ACF), reference FM100 198B, are used before and after an oxidizing procedure with H3PO4 to study the adsorption of Pb2+. The point of zero charge was determined for the modified and unmodified fiber giving values of 2.3 and 4.3, respectively. After oxidizing the ACF, the fiber showed to have a greater Pb2+ adsorption capacity in comparison with the unmodified fiber, which is related with the acid sites increase, where lead was mainly adsorbed. Determination of the BET area was carried out by nitrogen physisorption at 77K. ACFs presented superficial areas between 1000 and 1500 m²/g showing mostly, a microporous structure. The preliminary design of an adsorbent using the modified fiber is presented where the fiber superior physicochemical properties over the unmodified one are observed.

Synthesis and characterization of activated carbon fibers from Kevlar

Kevlar [poly (p-phenilylene terephtalamide)], was used as a precursor in the preparation of activated carbon fibers. For this intention, physical and chemical activations were carried out. Activated fibers were physically prepared from the carbonization of the Kevlar and its later activation with CO2 and steam of water, by the other hand; the chemically activated fibers were obtained by means of the impregnation of the material with phosphoric acid and their later carbonization. Different conditions were used and preliminary analyses of the precursor were taken into account (TGA-DTA / IR). The resulting fibers were characterized by N2 (77K) adsorption, infrared spectroscopy, SEM, and immersion calorimetry. Yields and Burn off were also evaluated. The results shows that if you want to synthesize activated carbon fibers from Kevlar strong conditions respect to the commonly used such as water steam, high phosphoric acid concentrations and methods of impregnation are the ones who allows the development of optimal surface areas and pore volumes.

Physicochemical and sensory changes in aged sugarcane spirit submitted to filtering with activated carbon filter

Sugarcane spirit is a drink considered as a national symbol of Brazil. It is produced by large producers and by about 30 thousand small and medium home-distilling producers dispersed throughout the country. The copper originating from the home-distillers can become a serious problem since at high concentrations in beverages it may cause serious human health problems. Therefore, the objective of this study was to investigate the influence of the activated carbon used in commercial filters on the physicochemical and sensory characteristics of aged sugarcane spirit. Analyses of copper, dry extract, alcoholic degree, higher alcohols, volatile acids, aldehydes, esters, furfural, and methanol were performed. The sensory evaluation was performed by seven selected trained judges, who analyzed the yellow color, woody aroma and flavor, and intensity of alcoholic aroma and flavor of the cane spirit before and after the filtration process. The sensory tests were carried out using a 9 cm non-structured intensity scale. A reduction was observed in all compounds analyzed physicochemically, except for the esters, which increased after filtration. This increase is probably due to the esterification of the alcohols and acids present. According to the sensory results obtained, a reduction was observed in the intensity of the yellow color, aroma, and wood flavor characteristics, the major characteristics of the aging process.

Caracterización del proceso de adsorción de 3-cloro fenol desde solución acuosa sobre carbon activado por calorimetria de inmersión

The immersion enthalpy of activated carbon in 3-chlorophenol solutions, of 100 mg L-1, is determined at different pH values between 3 and 11 with results between 37.6 and 21.2 J g-1. The 3-chlorophenol adsorbed quantities on the activated carbon during the calorimetric experience, are between 1.13 and 2.19 mg g-1, for different pH values of the solution. The 3-chlorophenol adsorbed quantity and the immersion enthalpy decrease by increasing of the pH solution, while increasing the adsorbed quantity increases the immersion enthalpy value.

Relación entre la entalpía de inmersión de monolitos de carbon activado y parametros texturales

In this study, Disc and honeycomb-shaped activated carbon monoliths were obtained using as a precursor coconut shell, without the use of any binder. Textural characterization was performed by adsorption of N2 at 77 K and immersion calorimetry into benzene. The experimental results showed that the activation with zinc chloride produces a wide development of micropores, yielding micropore volumes between 0,38 and 0,79 cm³ g-1, apparent BET surface area between 725 and 1523 m² g-1 and immersion enthalpy between 73,5 and 164,2 J g-1.Were made comparisons between textural parameters and energy characteristics.

Estimation of surface area and pore volume of activated carbons by methylene blue and iodine numbers

Data of methylene blue number and iodine number of activated carbons samples were calibrated against the respective surface area, micropore volume and total pore volume using multiple regression. The models obtained from the calibrations were used in predicting these physical properties of a test group of activated carbon samples produced from several raw materials. In all cases, the predicted values were in good agreement with the expected values. The method allows extracting more information from the methylene blue and iodine adsorption studies than normally obtained with this type of material.

Avaliação de filtros domésticos comerciais para purificação de águas e retenção de contaminantes inorgânicos

Twenty domestic commercial filters, in order to determine the percentual retention of color, turbidity, dry residue, bicarbonates, carbonates, total hardness, nitrogens, iron, chlorides, fluorides, and residual chlorine (parameters of food legislation) and sulphides in thirteen water samples proceeding from springs, wells, rivers, lakes, drinking patterns and standards, before and after purification were evaluated. The results showed that purifiers presented adequate retention for nitrates (74.8 ± 16.2 %) and residual chlorine (74.0 ± 11.2) and medium retention for sulphides (61.7 ± 11.3); while porcelain plus activated carbon filters presented adequate retention for color (90.0 ± 19.7), turbidity (76.4 ± 18.4) and iron (83.5 ± 15.1). Therefore the retention of carbonates, bicarbonates, total hardness, chlorides, dry residue, fluorides, ammonium nitrogens and nitrites was less than 10%, and the values of pH didn't show significant variation, for all the filters studied.

Pré-concentração de nitrosaminas a partir de amostras aquosas por extração em fase sólida e cromatografia capilar eletrocinética micelar

This paper describes the development of a methodology for solid phase extraction (SPE) and pre-concentration of nitrosamines from aqueous samples using granular activated charcoal as stationary phase. micelar electrokinetic capillary Chromatography (MEKC) was used for the separation and identification of the nitrosamines in the extracts. Using a sample with 50 µg l-1 of each nitrosamines standards (dimethylnitrosamine, DMN; diethylnitrosamine, DEN; N-nitrosopyrrolidine, NPYR; N-nitrosopiperidine, NPIP; N-nitrosomorpholine, NMOR), the methodology showed a range of recuperation from 29 to 107% with a linear zone between 10 and 500 µg l-1. The developed methodology can be applicable to the determination of these analytes in different aqueous samples.

Emprego do carvão ativado para remoção de cobre em cachaça

Copper content is of great concern among sugarcane-spirit producers. It is released from copper-made distillers, during the distillation process. Activated carbon has been used to remove copper. However, depending on the amount of carbon and the duration of reaction, it can also remove higher alcohols and esters, which are important in the final product. A sugarcane spirit with 9 mg L-1 of copper was shaken with 2 to 26 g L-1 of activated carbon, during 10 to 1440 minutes. Then, copper and organic compounds were measured. At least 12 g L-1 of carbon and 60 min shaking time were necessary to decrease copper bellow 5 mg L-1. However, other components of the product were also affected.

O emprego de quitosana quimicamente modificada com anidrido succínico na adsorção de azul de metileno

The adsorption capacity of alpha-chitosan and its modified form with succinic anhydride was compared with the traditional adsorbent active carbon by using the dye methylene blue, employed in the textile industry. The isotherms for both biopolymers were classified as SSA systems in the Giles model, more specifically in L class and subgroup 3. The dye concentration in the supernatant in the adsorption assay was determined through electronic spectroscopy. By calorimetric titration thermodynamic data of the interaction between methyene blue and the chemically modified chitosan at the solid/liquid interface were obtained. The enthalpy of the dye/chitosan interaction gave 2.47 ± 0.02 kJ mol-1 with an equilibrium constant of 7350 ± 10 and for the carbon/dye interaction this constant gave 5951 ± 8. The spontaneity of these adsorptions are reflected by the free Gibbs energies of -22.1 ± 0.4 and -21.5 ± 0.2 kJ mol-1, respectively, found for these systems. This new adsorbent derived from a natural polysaccharide is as efficient as activated carbon. However 97% of the bonded dye can be eluted by sodium chloride solution, while this same operation elutes only 42% from carbon. Chitosan is efficient in dye removal with the additional advantage of being cheap, non-toxic, biocompatible and biodegradable.

Pré-tratamentos de melaço de cana-de-açúcar e água de maceração de milho para a bioprodução de carotenóides

This work studied the pretreatment of sugarcane molasses (CM) and corn steep liquor (CS) for the production of carotenoids by Sporidiobolus salmonicolor (CBS 2636). The acid pretreatment removed less micronutrients than that with activated carbon and led to high removals of Cu and Mn. Reduction in optical density of the prepared medium and removal of glucose from it were 22% and 7% for CM and 95% and 38% for CS, respectively. Total carotenoids obtained with substrates pretreated with acids (541 mg/L) were higher than the results obtained when the medium was treated with activated carbon (208 mg/L).

Remoção de chumbo(II) em sistemas descontínuos por carvões ativados com ácido fosfórico e com vapor

Adsorption of heavy metal cations by activated carbon is dependent on the capacity of the material in promoting adsorption and the time needed to reach equilibrium. Carbon samples were previously activated either by phosphoric acid treatment at 400 ºC or by steam at 800 ºC. The results of Pb(II) adsorption by these activated carbons have shown that equilibrium was typically reached within the first 5 min of contact between carbon and metal solution, with a maximum adsorption capacity higher than 69 mg g-1 for the vapor-activated sample. Temperature influences the sorption capacity, which corresponds to an endothermic process. Lead(II) retention is more pronounced at high temperature and low pH.