This study investigates the potential use of amino-functionalized silica gel as an adsorbent for the recovering of congo red dye from aqueous solution. The effects of pH, contact time, and temperature were determined and evaluated. Equilibrium isotherms were also studied. The adsorption kinetics was modeled by pseudo-first order and pseudo-second order. Furthermore, desorption of congo red was preliminarily studied. The pH range from 4.5 to 7.0 was favorable for the adsorption of congo red onto amine modified silica at 25ºC. Higher adsorption capacity was obtained at 50ºC. Langmuir and Freundlich models were fitted to the adsorption equilibrium data. The best fittings were obtained with the pseudo-second order and Langmuir model for kinetics and equilibrium, respectively. Desorption studies suggest that ion exchange might be the major mode of adsorption. KOH solution was the best desorbing agent for recovering the adsorbed dye.

ResumoNo presente trabalho, processos de oxidação avançada, Fe 2+ /H 2 O 2 e UV/H 2 O 2 , e de fotólise (UV) foram empregados na descoloração de dois efluentes sintéticos, contendo corantes tipo índigo e azo, e de um efluente de lavanderia industrial. Experimentalmente, soluções em concentração de 20 mg/L dos corantes índigo carmim e vermelho congo, respectivamente 43 µmol/L e 29 µmol/L, e o efluente têxtil (pH = 3) foram submetidos a diferentes condições oxidantes sob temperatura ambiente (27 ºC). As remoções de cor e de DQO foram avaliadas em cada sistema oxidativo estudado. Em geral, os resultados obtidos mostraram que os processos utilizados são muito promissores na descoloração dos efluentes. A descoloração completa das soluções foi alcançada nos processos Fenton e com UV/H 2 O 2 . Estudos cinéticos revelam que a taxa de descoloração em meio aquoso segue uma cinética de pseudo-primeira ordem em relação à concentração do corante.Palavras-chave: corantes sintéticos; efluente têxtil; processos de oxidação avançada; descoloração; cinética. AbstractIn the present work, advanced oxidation processes, Fe 2+ /H 2 O 2 and UV/H 2 O 2 , and direct photolysis (UV light) have been applied in the decolorization of two synthetic wastewater containing indigo and azo dyes and laundry effluent. Individual aqueous solutions containing 20 mg/L indigo carmine and congo red dyes (43 µmol/L and 29 µmol/L, respectively) and textile laundry wastewater at pH 3 were subjected to different experimental conditions in the oxidation reactions at room temperature (27 o C). Color and COD removals were evaluated for each oxidation systems. The results showed that the utilized processes are able to successfully decolorize the wastewaters. Complete bleaching was achieved by Fenton and UV/H 2 O 2 . Also, kinetics investigations revealed that the decolorization follows pseudo-first order kinetic with respect to the dye concentration.

Saxitoxin (STX) is the most toxic non-protein substance known. STX-producing cyanobacteria have been identified in most continents and are being detected more widely because of global warming, threatening human drinking water supplies worldwide. Removal of these components can be accomplished by adsorption on granular-activated carbon (GAC) but little is yet known about the kinetics of the process. This research investigated adsorption kinetics and diffusion behaviour of a decarbomoyl saxitoxin (dc-STX) and a carbamate toxin (STX) on four coconut shell-based GAC samples with different pore size distribution. It was observed that equilibrium concentration was reached within 24 h and that a pseudo-second-order model best represented experimental data. Of the four GAC samples tested, the example with the largest volume of mesopores adsorbed more STX and with a faster upload rate, while dc-STX was adsorbed equally in all four GAC samples.

Liquid phase adsorptive separations are found in several industrial applications such as the recovery of p-xylene from its isomers. In this study, the headspace experimental technique was used to measure pure and multicomponent adsorption equilibria of liquid xylenes in Y zeolite. Data for pure-component equilibrium were determined at temperatures between 80 and 1208C and correlated using the Extended Langmuir model. The parameters for pure components estimated from the correlated data showed good agreement with data reported in previous studies and relatively low deviations when compared to the experimental data dispersion. Using the pure-component data, two models were tested for multicomponent (binary and quaternary) equilibrium correlation: Ideal Adsorbed Solution (IAS) model and Extended Langmuir Multicomponent model. The results from the IAS model did not conform well to the experimental results, indicating the existence of significant nonidealities in the system. The Extended Langmuir model predicted values generally in

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