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

Cerebral gene expression in response to single or combined gestational exposure to methylmercury and selenium through the maternal diet

Controversy remains regarding the safety of consuming certain types of seafood, particularly during pregnancy. While seafood is rich in vital nutrients, it may also be an important source of environmental contaminants such as methylmercury (MeHg). Selenium (Se) is one essential element present in seafood, hypothesised to ameliorate MeHg toxicity. The aim of the present study was to ascertain the impact of Se on MeHg-induced cerebral gene expression in a mammalian model. Microarray analysis was performed on brain tissue from 15-day-old mice that had been exposed to MeHg throughout development via the maternal diet. The results from the microarray analysis were validated using qPCR. The exposure groups included: MeHg alone (2.6 mg kg−1), Se alone (1.3 mg kg−1), and MeHg + Se. MeHg was presented in a cysteinate form, and Se as Se–methionine, one of the elemental species occurring naturally in seafood. Eight genes responded to Se exposure alone, five were specific to MeHg, and 63 were regulated under the concurrent exposure of MeHg and Se. Significantly enriched functional classes relating to the immune system and cell adhesion were identified, highlighting potential ameliorating mechanisms of Se on MeHg toxicity. Key developmental genes, such as Wnt3 and Sparcl1, were also identified as putative ameliorative targets. This study, utilising environmentally realistic forms of toxicants, delivered through the natural route of exposure, in association with the power of transcriptomics, highlights significant novel information regarding putative pathways of selenium and MeHg interaction in the mammalian brain

Coordination of Adsorbed Boron: A FTIR Spectroscopic Study

We studied B adsorption on amorphous aluminum and iron hydroxides, allophane, and kaolinite as a function of pH and initial B concentration. Boron adsorption lowered the point of zero charge of all four adsorbents, implying specific adsorption (inner-sphere complexation) of B. We provided novel information on the coordination of B adsorbed at mineral-water interfaces by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The ATR-FTIR spectra of interfacial B species were influenced by pH and mineral type. Strong trigonal B and weak tetrahedral B bands of the asymmetric stretching mode were observed on the difference spectra at pH ≈7 for amorphous iron hydroxide, whereas both strong trigonal and tetrahedral B bands were found at pH ≈10 . A strong IR band of asymmetric stretching of tetrahedral B shifted to higher frequencies in am-Fe(OH)3 paste at both pH’s relative to that of boric acid solution at pH 11. Trigonal B asymmetric stretching bands shifted to higher frequencies on the difference spectra for am-AI(OH)3 and allophane at both pH’s compared to that of boric acid solution at pH 7. Polymerization of B on mineral surfaces is shown to be possible. The results provide spectroscopic evidence that both B(OH)3 and B(OH)4- are adsorbed via a ligand exchange mechanism