Effective adsorption and enhanced degradation of various pesticides from aqueous solution by Prussian blue nanorods

Organophosphorus pesticides are most popular and broadly used owing to high-efficiency and organochlorines have longer persistence and irregular use in developing countries. The potential of bioaccumulation and persistence coupled with their toxicity call for development of effective low-cost elimination methods Prussian blue (Iron hexacyanoferrate; FeHCF) and its analogues have been widely employed in several applications due to outstanding characteristics (high surface area and photo-induced properties). Hence, highly crystalline and sharp hexagonal nanorods (<60 nm) of FeHCF were synthesized using Sapindus-mukorossi and subsequently used for degradation of toxic pesticides; α-hexachloro cyclohexane (α-HCH), malathion and chlorpyrifos (CP). Under sunlight, a rapid initial exponential decrease in concentration of each pesticide (50 mg L−1) over time revealed high adsorption capacity of catalyst (surface area: 69.38 m2/g). Statistics supported first order degradation kinetics and Langmuir isotherms at optimum photocatalyst-dose (25 mg) and neutral pH. Within 12 h, high degradation (%) of malathion (95%; t1/2 = 2.3 h) on acidic surface of catalysts followed by CP (92%; 4 h) and α-HCH (90%; 5.8 h) may attributed to high electron density. The lowest photodegradation of α-HCH might be due to its high stability and resistance towards oxidation. The finding of GC–MS peaks for small byproducts (glycerol, butyric acid, butane-1,2,4-triol, 3,4,4-trihydroxybut-3-en-2-one, phosphonic acid, and butane-1,4-diol) clearly supported free radical (OH) based oxidation of pesticides. Besides, FeHCF catalyst (with low band gap) can be easily photo-activated. Overall, greater active sites, high surface activity, low band gap and semiconducting nature of FeHCF make it promising photocatalyst for waste-water-treatment.