Removal and photodegradation of Alizarin by CdS quantum dot modified activated carbon

In the past decades, numerous investigations were done on the production and application of different types of activated carbons and other affordable adsorbents from natural wastes such as agricultural residues [1]. Besides the application of these low-cost materials, the application of oxidation processes using nanomaterials has gained great attention for wastewater treatments, in the recent years [2]. Quantum dots (QDs) are a group of these nanomaterials that have been used extensively for photocatalytic degradation of dyes and other organic pollutants. But, application of free QDs was associated with some difficulties, such as oxidation and agglomeration of QDs and difficulties in separation.In this article, the preparation and application of CdS quantum dot modified activated carbon for removal and photodegradation of Alizarin in wastewaters are studied. Firstly, activated carbon is prepared from fruit wastes. Then, CdS quantum dot loaded activated carbon nanocomposites are prepared and finally the efficiency of these prepared materials for removal and photocatalytic degradation of alizarin (as a pollutant dyestuff) is studied.To examine the photocatalytic activity of prepared catalysts, 250 mg of desired catalyst dispersed in 24 mL double distilled water and then 6 mL of alizarin aqueous solution (250 ppm) was added and stirred in dark place for 60 min to attain an adsorption/desorption equilibrium. Afterwards, the suspension was irradiated by sunlight under moderate stirring. The temperature of the solution was fixed by a water bath to prevent any heating effect on results. At specified time intervals, the concentration of dye in the supernatant was determined by UV–vis absorption spectroscopy at the λmax=435 nm [3]. In the next stage, the kinetic and isotherm of adsorption is studied; and a mechanism for photocatalytic dye degradation is proposed. Results are shown that the prepared nanocomposites have both of adsorption and photocatalytic degradation properties, and could be used for degradation and decolourization of dyes in the wastewater purification methods.