Abstract
Gemini surfactants, with double hydrophilic and hydrophobic groups, offer potentially orders of magnitude greater surface activity compared to similar single unit molecules. A cationic Gemini surfactant (Propyl didodecyldimethylammonium Bromide, PDDDAB) and a conventional cationic surfactant (Dodecyltrimethylammonium Bromide, DTAB) were used to pre-treat and generate activated carbon. The removal efficiency of the surfactant-modified activated carbon through adsorption of chromium(VI) was investigated under controlled laboratory conditions. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to investigate the surface changes of surfactant-modified activated carbon. The effect of important parameters such as adsorbent dosage, pH, ionic strength and contact time were also investigated. The chromium(VI) was adsorbed more significantly on the Gemini surfactant-modified activated carbon than on the conventional surfactant-modified activated carbon. The correlation coefficients show the data best fit the Freundlich model, which confirms the monolayer adsorption of chromium(VI) onto Gemini surfactant-modified activated carbon. From this assessment, the surfactant-modified (especially Gemini surfactant-modified) activated carbon in this study showed promise for practical applications to treat water pollution.
Highlights
IntroductionCommon occurrence in industrially affected environments, chromium pollution has gained a high profile [1]
Because of its ecotoxicity, and common occurrence in industrially affected environments, chromium pollution has gained a high profile [1]
The relationship between the adsorption time T and the chromium removal rate was plotted as removal rate falls from 92% to about 80%, DTAB-AC adsorption chromium removal rate falls from found to be slightly decreased, which may be attributed to physical desorption of Cr(VI) from activated
Summary
Common occurrence in industrially affected environments, chromium pollution has gained a high profile [1]. The hexavalent oxidation state of chromium is more toxic than other forms in water and can cause serious illness or even death [2,3]. Approaches using adsorption are considered to have potentially the best treatment effect [8]; modified activated carbon can enhance the adsorption performance of activated carbon, and potentially provides a high efficiency and low cost adsorbent for treating chromium(VI) pollution [9,10]. Activated carbon adsorption is non-selective, and the adsorption process is susceptible to interference, especially metal cations, and many studies show that surfactant-modified activated carbon can enhance the adsorption capacity of metal ions [11]. Peñas-Sanjuán [13] used polyalkylamine as the activated carbon surfactant, it has excellent removal performance for Pd (II)
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