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This work involves the application of carbon xerogels in the removal of two emerging contaminants, caffeine and diclofenac, from aqueous solutions. Textural characterization of the carbon xerogels prepared by polycondensation of resorcinol with formaldehyde (with a molar ratio of 1:2) has been investigated using N 2 adsorption-desorption at-196 o C. Chemical surface groups were analyzed by FTIR spectroscopy, elemental microanalysis and determination of isoelectric point. The equilibrium tests were carried out using different weights of adsorbent and the experimental data were best correlated by Sips isotherm equation. The kinetic experimental data were described using pseudo-first and pseudo-second order kinetic models, being well described by a pseudo-second order model. The maximum adsorption capacity was observed for adsorption of caffeine onto a xerogel treated with urea solution (182.5 mg.g-1), due to the presence of Lewis bases on its surface, which increase the adsorption affinity for organic compounds. On the other hand, the higher extent of diclofenac adsorption was obtained with a carbon xerogel treated with sulphuric acid (80.0 mg.g-1), mainly due to electronic interactions. Comparing these results with other data reported in the literature, the carbon xerogels employed in our study were found to exhibit comparable adsorption capacities and higher kinetic properties.

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In this work, a novel process for lactic acid purification based on ion exchange is proposed. It consists of two stages: first, a strong cation resin was used to reduce the broth pH below the pK a of lactic acid (3.86) and remove the cations present in the solution; then lactic acid was separated from the other anions in the broth using a weak anion exchanger. The ion exchangers selected were Lewatit S2568H and Lewatit S3428 (Bayer, Germany). The Lewatit S2568H resin retained the cations in the broth with an apparent capacity of 1.7 equiv/ L, reducing the broth pH below 3.86. It was able to decrease the pH of the broth to as low as 1.5, generating 4 bed volumes (BV) of acidified and partial demineralized broth. In the second step, the acidified broth was purified by the Lewatit S3428 resin, which retained the other anions present in the broth, producing an aqueous solution of lactic acid. This resin was able to produce 25 BV of purified lactic acid with selectivity higher than 99.9%. The final purity of lactic acid was higher than 99%.