No abstract

No abstract

No abstract

No abstract

Studies have been conducted on detoxification of hemicellulose hydrolysates, but an effective detoxification method remains to be developed. The use of layered double hydroxides (LDHs) as adsorbents may be a solution to this problem. In this study, LDHs composed of 30, 63, or 70% MgO were used in their uncalcined and calcined states to adsorb acetic acid, formic acid, hydroxymethylfurfural, and furfural from a synthetic hemicellulose hydrolysate. Kinetic studies revealed that calcined LDH composed of 70% MgO (MG70c) had the best performance: it was able to remove 73% of acetic acid and 90% of formic acid in 6 h of incubation at 50 °C. Hydroxymethylfurfural and furfural were not adsorbed (C/C 0 ≈ 1) by calcined or uncalcined LDHs under the studied conditions. The adsorption equilibrium was determined at different temperatures. Adsorption isotherms were best described by the Langmuir−Freundlich model. These results show the potential of MG70c to remove acetic and formic acids from hemicellulose hydrolysates, thereby increasing their suitability as fermentation substrates.

Water reuse in industrial processes has been an increasing need encouraged in recent years. However, as the streams are recycled, solutes accumulate, thus requiring purification techniques. Membrane processes (reverse osmosis and electrodialysis) have been implemented and in order to increase the reuse of water at its highest level, crystallization has been evaluated to remove salts from the concentrate produced and get a feasible disposal. Nevertheless, contaminants affect the crystallization performance, thus making the removal of residual organics important for both the efficiency of crystallization and the increase of water reuse. In this context, aiming at establishing a sustainable virtuous circle, bone char (0.5-1.4 mm particle size, mesoporous structure) was used to remove refractory organics from an electrodialysis concentrate effluent (C-EDR) from a Brazilian petroleum refinery, at a lab-scale, in a fixed-bed adsorption column. Bone char selectively and partially removed the refractory organics, a complex mixture of long-chain hydrocarbons, aromatic compounds, carboxylic acids, amines and amides. The maximum adsorption capacity increased with the increase in bed depth and reduction in flow rate. A maximum removal of 35.60 mg g was achieved for the highest bed depth evaluated (12.9 cm). The breakthrough curves indicated that bone char could adsorb part of the organic compounds from the C-EDR. The scaling up was possible for the C/C ratios of 0.55, 0.60 and 0.65, providing a service time at about 16 days for 45% removal efficiency for typical real operational conditions used in the refinery.

In this study, we evaluated the adsorption of gold ions onto sericin and alginate particles chemically crosslinked by proanthocyanidins (SAPAS) in a fixed-bed column aiming at establishing a new profitable application for sericin. The effects of the feed flow rate and the gold inlet concentration on the breakthrough curve behavior were investigated. A breakthrough time of more than four and a half days with a removal efficiency of 98.39% (maximum removal capacity of 57.91 mg/g) was obtained for the breakthrough curve performed at the lowest feed flow rate and the lowest gold inlet concentration (0.4 mL/min and 53.18 mg/L, respectively). All breakthrough curves were best described by the Yan et al. model. The two adsorption/desorption cycles performed using thiourea (0.5 M)/hydrochloric acid (0.5 M) as the eluent resulted in low values of gold recovery percentage (recoveries of 24.98 and 22.6% for the first and second cycle, respectively), which indicated the predominance of chemical interactions between SAPAS and gold. On the other hand, an efficient recovery of gold (89.00%) was achieved from the association between the adsorption and incineration processes. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicated that gold was reduced from Au­(III) to metallic gold during the adsorption process.

Partículas a base de sericina e alginato foram produzidas com diferentes concentrações (5, 15, 25 e 35 g/L) do agente reticulante proantocianidinas (PAs) e do polímero álcool polivinílico (PVA), visando à obtenção de partículas de baixa solubilidade em meio aquoso para aplicação na remoção de íons metálicos nobres presentes em efluentes por bioadsorção. Devido à baixa solubilidade em meio aquoso (3,56 ± 0,21 %) da partícula composta de 25 g/L sericina / 20 g/L alginato / 25 g/L PAs, esta foi caracterizada por análise de microscopia eletrônica de varredura (MEV), microcopia ótica (MO) e espectoscopia de infravermelho com transformada de Fourier (FTIR).