This paper reports a study on the adsorption of the dye sunset yellow, present in an aqueous synthetic solution and a real effluent from a soft drink plant, onto granular-activated carbon derived from coconut husks, using a batch system. The kinetic equilibrium was investigated using two different dye concentrations (10(2) and 10(3) mg L(-1)) at 25 degrees C and 150 rpm. The adsorption isotherms and thermodynamics parameters were evaluated at 25 degrees C, 35 degrees C, 45 degrees C and 55 degrees C, using the synthetic and real effluents (5-10(3) mg L(-1)). Experimental data showed that the adsorbent was effective in the removal of sunset yellow dye and the contact time required to attain the adsorption equilibrium did not exceed 10 h. The adsorption capacity was not influenced within a wide range of pH values (1-12), although at high dye concentrations it increased with increasing temperature for both the synthetic and real effluents. The Redlich-Peterson isotherm best represented the equilibrium data of the system. The negative values obtained for DeltaG0 and DeltaH0 suggest that this adsorption process is spontaneous, favourable, and exothermic. The positive values for DeltaS0 indicate an increase in the entropy at the solid/liquid interface. Based on the results of this study, adsorption appears to be a promising method for the removal of sunset yellow azo dye from effluent generated at soft drink plants.
RESUME -Coomassie Brilliant Blue (CBB) is a commonly dye present in the waste of the textile industry. Its use produces waste which must be treated before being discharged into rivers or sewage. Combined processes have been used with efficiency for wastewater treatment. This study aims to evaluate the combined process of photo-Fenton and adsorption for the degradation and removal of the dye CBB in aqueous solution. Initially, the CBB was submitted to photo-Fenton oxidation. Photo-Fenton oxidation degraded 76,9% of the initial CBB concentration, which was not enough to satisfies the Brazilian legislation. The fixedbed adsorption was conducted for 13 hours, and during all this period the outlet concentration was always lower than the breakpoint, being this concentration in compliance with the legislation. The combined photo-Fenton/Fixed-bed adsorption was effective in the CBB removing (at least 95,9%).
The aim of this study was to evaluate thesynthetic azo dye (tartrazine) biosorption onto second line silkworm cocoons. Batch adsorption system was used to investigate the effect of pH and initial tartrazine concentration in theliquid phase. Also, the kinetic mechanismwas investigated at 20°C and pH 2.0.The highest adsorption was obtained at the lowest pH evaluated, while the assays with pH above 3.0 did not show significant adsorption at the first hour of theprocess, indicating that biosorption is more favorable at lower values ofpH.The adsorption kinetic was studied at pH 2.0andcompared withthe kinetic mechanism ofconvective mass transfer and diffusion models.The kinetic behavior of biosorption process showed a high amount of dye adsorbedat the beginning of the process, however, after saturation of the functional groups, the adsorption rate decreased over time until saturation. After 24 hours of batch operation, the uptake of tartrazine onto silkworm cocoons was 40.39 mg g-1,and the rate of adsorption reduces from 3.430 to 0.003 mg min-1g-1, suggesting that the process approaches the equilibrium. The Crank model provided the best fit. The results revealed that silkworm cocoons have the potential to be used as a biosorbent for wastewater treatment containing tartrazine
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