Very fast catalytic reduction of 4-nitrophenol, methylene blue and eosin Y in natural waters using green chemistry: p(tannic acid)–Cu ionic liquid composites

Abstract

Using tannic acid (TA) as a biopolymer, poly(tannic Acid) (p(TA)) microgels were obtained by cross-linking TA with trimethylolpropane triglycidyl ether (TMPGDE) as cross-linker in a water-in-oil micro emulsion system. Ionic liquid forms of p(TA) micro particles were prepared as Ionic Liquid Colloids (ILC) by post chemical modification of p(TA) particles using quaternization agents such as 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPACl) and ammonia (NH₃) in aqueous solution to generate positively-charged ammonium salts on the network. Then the modified p(TA) micro particles were used as template for Co, Ni, and Cu metal nanoparticle preparation in situ after loading of metal salts such as CoCl₂, NiCl₂, and CuCl₂ from ethyl alcohol solution into the p(TA) network, and consequent reduction with sodium borohydride (NaBH₄). The prepared metal nanoparticle-containing ILCs of p(TA) microgel composites were used as catalysts in the reduction of toxic organic compounds such as 4-nitrophenol (4-NP), eosin Y (EY), and methylene blue (MB). Various parameters affecting the 4-NP and MB reduction were investigated. The activation energy, enthalpy, and entropy for the reduction of 4-NP to 4-AP catalyzed by ILC p(TA)-co composite catalyst system were calculated as 26.19 kJ mol⁻¹, 23.12 kJ mol⁻¹, and −182.35 J mol⁻¹ K⁻¹, respectively.