Abstract:
The objective of this research is to study adsorption efficiency and phenomenon of ionic dyes (reactive black 5 (RB5) and basic yellow 1 (BY1)) by using digested sludge from wastewater treatment system comparing with commercial-grade powder activated carbon (PAC). Effects of acid or base surface treatment, pH, temperature on ionic dyes adsorption capacities were investigated by batch experiments. Moreover, the selective adsorption between nonionic surfactant (TX-100) and ionic dyes was also studied. The results have showed that the sludge-type and PAC-type adsorbents can adsorb both types of dyes and reach the equilibrium state within 60 and 360 minutes, respectively. While the adsorption of TX-100 corresponds with 60 minutes for reaching the equilibrium state. All adsorbents kinetic data can be described by using pseudo-second order equation. Moreover, RB5 had the highest adsorption capacity at pH 9 and pH 7 for base-treated PAC and sludge, respectively. Whereas, BY1 had highest adsorption capacities by acid-treated PAC and sludge at pH 9. This conforms with the pHPZC values. Adsorption isotherms can be explained by Langmuir isotherm for all PAC group and both Langmuir and Freundlich isotherms for all sludge group. The endothermic system is likely occurred in this study. Due to the selective adsorption experiments in bi-solution, lower adsorption capacities for both ionic dyes and TX-100 by all PAC group can be observed, except in the cases of BY1 adsorption by untreated PAC that there is insignificant variation on TX-100 adsorption. On the other hand, by using sludge group, the adsorption capacity of TX-100 reduced, while ionic dyes are roughly constant. Note that, in case of acid-treated sludge and base-treated sludge, the different phenomena compared previous experimental results with RB5 dye obtained with dried sludge was investigated. For non-treated sludge, the treatment cost for removal BY1 was lower than that for using PAC.