Publication

Abstract : Cr(VI) is a highly toxic inorganic water pollutant and shows adverse effects on human health. Photocatalytic treatment is a green and efficient method to reduce the toxic Cr(VI) to non-toxic Cr(III). In general, photocatalysts are used in slurry form, which turns the post purification such as separation and re-use of the catalyst tedious. To overcome this limitation, in this article we describe the immobilization of visible light/sunlight active photocatalyst i.e. fibrous red phosphorus (FRP) on quartz sand (QS). FRP is a crystalline allotrope of red phosphorus with interesting structural features and optimum bandgap i.e. ~ 1.9 eV with sunlight/visible light activity. FRP immobilized QS was used as a photocatalyst for the reduction of Cr(VI) at different initial concentrations of Cr(VI) and with different loads of photocatalyst. High rate of Cr(VI) photoreduction was observed with 100 mg of FRP immobilized QS with a rate constant of 0.052 min−1. Immobilized photocatalyst was loaded in a tea bag and used as a “dip-photocatalyst” for the reduction of Cr(VI). In this process 80% of Cr(VI) reduction occurred in 60 min with a rate constant of 0.034 min−1. After the photocatalytic process, dip catalyst was dried under ambient conditions and re-used for the 2nd and 3rd cycles. Such immobilization of catalyst and using it in a tea bag as a dip catalyst facilitates the hassle free separation, re-use of the photocatalyst and eliminates the necessity of post purification processes and makes the photocatalytic environmental remediation processes more cost effective.