Abstract
ABSTRACT 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.
Highlights
In recent decades, contamination of ground and surface water by heavy metals and organic pollutants is a crucial factor of environmental problems
Further increasing of the pH results in a system sufficiently alkaline that makes the adsorbent surface negatively charged (TOR & CENGELOGLU, 2006; MITTAL et al, 2009; COTORUELO et al, 2010), which causes a strong repulsion between modified silica surface and anionic dye, inhibiting again the adsorption process
It was observed that the influence of the buffering in the adsorption of congo red onto Aminomodified silica (AMS) and CGS is insignificant, since deviations in the percentage removal were lower than 5%
Summary
Contamination of ground and surface water by heavy metals and organic pollutants is a crucial factor of environmental problems Among these contaminants are the dyes, which are discharged into water resources from many industries such as textile, pulp and paper, leather, cosmetics, plastics, paints, food and petrochemicals. Adsorption has been recognized as the most popular technique for the removal of non-biodegradable pollutants, including dyes, from wastewater, mainly due to its effectiveness, versatility and reliability compared to other conventional methods (AKSU, 2005; TOR & CENGELOGLU, 2006; LORENC-GRABOWSKA & GRYGLEWICZ, 2007; DONIA et al, 2009; MITTAL et al, 2009; AHMAD & KUMAR, 2010; SHARMA et al, 2011).
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