Potential of agro-industrial residues from the Amazon region to produce activated carbon.

Thousands of tons of residual lignocellulosic biomass are produced and discarded by agroindustries in the Amazon. These biomasses could be harnessed and used in the preparation of activated carbon, in view of the growing demand for this product with high added value, however, little is known about their characteristics, in addition to their potential as precursors of activated carbon. Therefore, the aim of this work was to evaluate the potential of four different biomasses in the preparation and quality of activated carbon. Residues from the processing of the fruits of acai, babassu, Brazil nut, and oil palm were collected, characterized, carbonized, physically activated with CO2, and characterized. The contents of the total extractives, insoluble lignin, minerals, holocellulose, and elemental (CHNS-O) were analyzed. The surface area and surface morphology were determined from the AC produced, and adsorption tests for methylene blue and phenol were performed. The four biomasses showed potential for use in the preparation of CA; the residues presented high contents of lignin (21.83-55.76%) and carbon (46.49-53.79%). AC were predominantly microporous, although small mesopores could be observed. The AC had a surface area of 569.65-1101.26 m2 g-1, a high methylene blue (93-390 mg g-1), and phenol (159-595 mg g-1) adsorption capacities. Babassu-AC stood out compared to the AC of the other analyzed biomasses, reaching the best results.

Biochars produced from various agro-industrial by-products applied in Cr(VI) adsorption-reduction processes.

This study aimed to reuse different agro-industrial by-products (poultry litter, pig manure, sewage sludge and coffee husk) for biochar production and to evaluate their Cr(VI) removal capacities in aqueous medium. The biochars showed different morphologies with porous structures. The percentages of Cr(VI) removal from solution were higher in acid medium (pH = 2), reaching values up to 87%. For all biochars, Cr(VI) removal occurs via both adsorption and reduction, being a rapid (30 min) process, which fits best to the pseudo-second order kinetic model. The biochars, especially from coffee husk, were able to reduce up to 20% of Cr(VI) to Cr(III). The maximum Cr(VI) removal capacities ranged from 10.86 mg g-1 (sewage sludge biochar) to 18.52 mg g-1 (coffee husk biochar). Therefore, the production of biochars from the agro-industrial by-products using the same experimental conditions in one single study is important to compare the Cr(VI) removal capacities from different biomasses. Thus, this study explored the corresponding raw material without the need of further treatment. Biochars showed potential for environmental applications considering Cr(VI)-polluted environments. It is hoped to provide basis to future studies using real wastewater samples.

Pretreatment Affects Activated Carbon from Piassava.

The specificity of activated carbon (AC) can be targeted by pretreatment of the precursors and/or activation conditions. Piassava (Leopoldinia piassaba and Attalea funifera Martius) are fibrous palms used to make brushes, and other products. Consolidated harvest and production residues provide economic feasibility for producing AC, a value-added product from forest and industrial residues. Corona electrical discharge and extraction pretreatments prior to AC activation were investigated to determine benefits from residue pretreatment. The resulting AC samples were characterized using elemental analyses and FTIR and tested for efficacy using methylene blue and phenol. All resulting AC had good adsorbent properties. Extraction as a pretreatment improved functionality in AC properties over Corona electrical discharge pretreatment. Due to higher lignin content, AC from L. piassaba had better properties than that from A. funifera.

Massaranduba Sawdust: A Potential Source of Charcoal and Activated Carbon.

This paper provides proof of concept that activated carbon (AC) may be readily produced using limited conversion methods and resources from sawdust of massaranduba (Manilkara huberi) wood, thereby obtaining value-added products. Sawdust was sieved and heat-treated in an oxygen-free muffle furnace at 500 °C to produce charcoal. The charcoal was activated in a tubular electric furnace at 850 °C while being purged with CO2 gas. Microstructural, thermal and physical properties of the three components: sawdust, charcoal and AC were compared by means of field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), density and water adsorption/desorption measurements. The resulting AC had a large surface area as measured by Brunauer-Emmett-Teller (BET) comparable to other such values found in the literature. The large surface area was due to pore development at the microstructural level as shown by FESEM. XRD illustrated that sawdust had a semi-crystalline structure whereas charcoal and AC evidenced mostly amorphous structures. TGA and DSC showed that AC had high reactivity to moisture compared to sawdust and charcoal.

Surface modification of activated carbon by corona treatment.

Surface modification may lead activated carbon (AC) to take on different properties. This study aimed to promote surface modification of activated carbons using corona treatment (electrical discharge). In this study, powdered commercial activated carbon was used. Activated carbons were subjected to corona treatment at different exposure times (2, 5, 8 and 10 min) at 4.5 cm height from the source. To observe differences promoted by treatment, activated carbons were analyzed by acidity, surface functional groups, Fourier Transform Infrared Spectroscopy (FTIR), elemental analysis (CHN), proximate analysis and thermogravimetry. Corona treatment impacted surface chemistry of activated carbons. There was a trend of increasing surface acidity according to exposure time. There were changes in functional groups, increasing carboxyl acid and decreasing lactone and phenol groups. FTIR analysis showed peaks in the bands at 3500, 1650 and 1300 cm-1. Increase of oxygen content and decrease of carbon content were also found. Immediate analysis followed similar tendency for volatile and fixed carbon content. There were also differences in thermogravimetry analysis. Treated activated carbons were different compared to virgin activated carbon. This difference was performed by surface oxidation. Thus, this study showed that corona treatment caused surface modifications and might impact adsorption process.

Bio-based thin films of cellulose nanofibrils and magnetite for potential application in green electronics.

The objective of this work was to prepare bio-based thin films and evaluate the additions of magnetite and glycerol on the physico-chemical (flexibility, wettability and barrier properties) and dielectric properties of cellulose/chitosan-based films. The films were prepared by solution casting and presented a suitable dispersion of the constituents observed by SEM and FTIR. The films were thermally stable up to 150 °C and had a higher flexibility, wettability and lower barrier properties upon addition of glycerol. The calculated dielectric constant (εr) for the composite films was based on measurements of capacitance, at 100 and 1000 Hz, with the additions of magnetite and glycerol more than doubling the εr increasing the charge storage capacity. The bio-based thin films have potential to be used as insulators in capacitors on the production of green electronics thus, reducing toxic and nonrenewable e-waste generation.

Amending potential of organic and industrial by-products applied to heavy metal-rich mining soils.

Mining activities promote the development of economies and societies, yet they cause environmental impacts that must be minimized so that their benefits overcome the likely risks. This study evaluated eco-friendly technologies based on the use of low-carbon footprint wastes and industrial by-products as soil amendments for the revegetation of Zn-mining areas. Our goal was to select adequate soil amendments that can be used to recover these areas, with a focus on low-cost materials. The amendments - limestone, sewage sludge, biochar, and composted food remains - were first characterized concerning their chemical composition and structural morphologies. Soil samples (Entisol, Oxisol, Technosol) from three different areas located inside an open-pit mine were later incubated for 60 days with increasing doses of each soil amendment, followed by cultivation with Andropogon gayanus, a native species. The amendments were able to change not only soil pH, but also the phytoavailable levels of Cd, Zn, and Pb. Limestone and biochar were the amendments that caused the highest pH values, reducing the phytoavailability of the metals. All amendments improved seed germination; however, the composted food remains presented low levels of germination, which could make the amendments unfeasible for revegetation efforts. Our findings showed that biochar, which is a by-product of the mining company, is the most suitable amendment to enhance revegetation efforts in the Zn-mining areas, not only because of its efficiency and cost, but also due to its low carbon footprint, which is currently the trend for any "green remediation" proposal.

Renewable hybrid nanocatalyst from magnetite and cellulose for treatment of textile effluents.

A hybrid catalyst was prepared using cellulose nanofibrils and magnetite to degrade organic compounds. Cellulose nanofibrils were isolated by mechanical defibrillation producing a suspension used as a matrix for magnetite particles. The solution of nanofibrils and magnetite was dried and milled resulting in a catalyst with a 1:1 ratio of cellulose and magnetite that was chemically and physically characterized using light, scanning electron and transmission electron microscopies, specific surface area analysis, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, catalytic potential and degradation kinetics. Results showed good dispersion of the active phase, magnetite, in the mat of cellulosic nanofibrils. Leaching and re-use tests showed that catalytic activity was not lost over several cycles. The hybrid material produced was tested for degradation of methylene blue dye in Fenton-like reactions resulting in a potential catalyst for use in degradation of organic compounds.

The use of piassava fibers (Attalea funifera) in the preparation of activated carbon.

The piassava fiber, residue of the broom industry, was used as precursor for the preparation of activated carbons (AC). AC were prepared by chemical activation with zinc chloride (AC ZnCl(2)) or phosphoric acid (AC H(3)PO(4)) and by physical activation with carbon dioxide (AC CO(2)) or water vapor (AC H(2)O). These materials were characterized by adsorption/desorption of N(2) to determine the BET areas, elemental analysis (CHN), thermogravimetric analysis (TG, DTA) and scanning electron microscopy (SEM). The carbons were tested with respect to their adsorption capacity of methylene blue, reactive red, phenol and metallic ions (Cr(+6), Cu(+2) and Zn(+2)). AC ZnCl(2) presented the highest surface area (1190 m(2)g(-1)) and AC H(3)PO(4), the largest pore volume (0.543 cm(3)g(-1)). AC ZnCl(2) was more efficient in the adsorption of methylene blue, Cr(+6) and Cu(+2) ions. AC H(2)O was the better adsorbent for phenol, while AC CO(2) was better for Zn(+2) ions.

Produção de carvão a partir de resíduo de erva-mate para a remoção de contaminantes orgânicos de meio aquoso / Production of charcoal from maté waste to remove organic contaminants from aqueous solution

Neste trabalho, apresenta-se um novo material adsorvente, obtido a partir da pirólise de resíduos da erva-mate. O carvão resultante demonstrou elevada área superficial específica quando comparado com outros materiais pirolisados e elevada capacidade de remoção de contaminantes orgânicos de soluções aquosas. Os valores de área específica apresentados pelos materiais foram de 344, 191 e ~0,5 m² g-1, para o carvão Mate 1, Mate 2 e Mate 3, respectivamente. As isotermas de adsorção mostraram que os carvões apresentam potencial para utilização como adsorvente para compostos orgânicos, tais como: o corante têxtil vermelho reativo, o corante azul de metileno e para o herbicida atrazina, sendo que os máximos de adsorção utilizando o carvão Mate 1 foram de 16, 230 e 30 mg g-1, respectivamente.

In this work we present a new adsorbent material, obtained by maté waste pyrolisis. The resulting charcoal presented high specific area when compared with other pyrolized materials and also high capacity to remove organic contaminants from aqueous solution. The charcoal showed specific area of 344, 191 and ~0.3 m² g-1 for sample Mate 1, Mate 2 and Mate 3, respectively. According to the corresponding adsorption isotherm these materials present good adsorption capacity for reactive textile and methylene blue dyes and the herbicide atrazine. Adsorption maxima were respectively 16, 230 and 35 mg g-1 for such substances, when sample Mate 1 was used.