The Role of Lactic Acid Adsorption by Ion Exchange Chromatography

Background: The polyacrylic resin Amberlite IRA-67 is a promising adsorbent for lactic acid extraction from aqueous solution, but little systematic research has been devoted to the separation efficiency of lactic acid under different operating conditions. Methodology/Principal Findings: In this paper, we investigated the effects of temperature, resin dose and lactic acid loading concentration on the adsorption of lactic acid by Amberlite IRA-67 in batch kinetic experiments. The obtained kinetic data followed the pseudo-second order model well and both the equilibrium and ultimate adsorption slightly decreased with the increase of the temperature at 293–323K and 42.5 g/liter lactic acid loading concentration. The adsorption was a chemically heterogeneous process with a mean free energy value of 12.18 kJ/mol. According to the Boyd _ plot, the lactic acid uptake process was primarily found to be an intraparticle diffusion at a lower concentration (,50 g/liter) but a film diffusion at a higher concentration (.70 g/liter). The values of effective diffusion coefficient D i increased with temperature. By using our Equation (21), the negative values of DGu and DHu revealed that the adsorption process was spontaneous and exothermic. Moreover, the negative value of DSu reflected the decrease of solid-liquid interface randomness at the solid-liquid interface when adsorbing lactic acid on IRA-67. Conclusions/Significance: With the weakly basic resin IRA-67, in situ product removal of lactic acid can be accomplishe

Geochemistry and spatial distribution of heavy metals in Oxisols in a mineralized region of the Brazilian Central Plateau

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)The majority of the soils of the Central Plateau of Brazil are product of long time development over stable surfaces, usually associated with erosion and re-deposition cycles. In this context, to successfully study the geochemistry and spatial distribution of heavy metals, it is essential to understand the geology as well as the geomorphology of the landscape and the properties of the metals related to their mobility. The main objective of this work was to evaluate contents of naturally occurring heavy metals (Co, Cu, Mn, Ni, Pb and Zn) in some highly weathered tropical soils as related to their geochemistry, geology and geomorphology. Additionally, it was aimed to interpret the spatial distribution patterns of these metals and of major elements (Al, Fe, Ti and Mg), evaluating the association and taking the influence of the geology and geomorphology into consideration. In geo-referenced sites, ranging from 480 to 1040 m in altitude, samples were collected at two depths (0-20 and 60-80 cm), ground, sieved, and prepared for analysis. Heavy metals and major element contents were determined by extraction with aqua regia. Descriptive statistics, Pearson correlation coefficients, Principal Components Analysis (PCA) and spatial variability analyses were conducted and soil metal concentrations for the whole area were predicted by kriging (interpolation). A close association between Pb, Zn, and Mn was observed using PCA and Pearson's correlation. Highest concentrations of Pb, Zn, and Mn were determined in soils between 650 and 550 m altitude surrounding the dolomite massif hills and Ambrosia and Fagundes mineral deposits. Copper and Fe were found to be geochemically associated with highest concentrations observed in soils formed from carbonaceous phyllite with quartzite layers. Cobalt and Ni concentrations were associated with areas characterized geomorphologically as alluvial-colluvial deposits at the lowest altitudes within the region. Although there is a marked dispersive action of tropical weathering on metal distribution in the region, Cu, Pb, and Zn were found spatially associated with their geological source. This probably happens because of greater affinity of those metals to Fe and Mn oxides formed predominantly under tropical conditions and present in higher concentrations near to the sources of these heavy metals. On the other hand, both the low affinity of Ni and Co for these oxide minerals and the region's geomorphology allowed for their migration towards the drainage network to the regions of sediment accumulation at lower altitudes during the landscape's evolution. (C) 2010 Elsevier B.V. All rights reserved.1602131142Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)project EMBRAPA Cerrados/IRD [0203205]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CNPq [475623/2003-7]CAPES [514-05]project EMBRAPA Cerrados/IRD [0203205

Competitive sorption of intermixed heavy metals in water repellent soil in Southern Australia

In water repellent soil, Cr, Pb and Cu showed higher adsorption intensities than Zn, Cd and Ni did. Soil water repellency is much more widespread than formerly thought. In order to promote fertility and productivity, the irrigation of recycled water onto water repellent soil may be an applied technology to be used in some areas of Southern Australia. Therefore, heavy metals in recycled water potentially enter into the soil. The competitive sorption and retention capacity of heavy metals in soil are important to be determined, especially considering the special geochemical origin of water repellent soil that was caused by waxes on or between the soil particles. Batch equilibrium sorption experiments on Cd, Cr, Cu, Ni, Pb and Zn in their typical proportion in recycled water were conducted in water repellent soil. The sorption intensity, sorption isotherm in the experiments together showed that Cr, Pb and Cu have higher sorption intensity than those of Zn, Ni and Cd in the competitive system. The risk assessment for the application of recycled water onto water repellent soil is definitely necessary, especially for the metal cations with relatively weak sorption.<br /