Synthesis of nanosized ZSM-5 zeolite from rice straw using lignin as a template: Surface-modified zeolite with quaternary ammonium cation for removal of chromium from aqueous solution

Abstract

Extracted silica and lignin from local rice straw were respectively used as a source of silica and a templating agent for the synthesis of nanosized ZSM-5 zeolite at different aging temperatures with the autoclave process. A comparative analysis between synthesized ZSM-5 with lignin (ZL) and its respective synthesized with most common tetrapropyl-ammonium bromide (TPABr) (ZT) using XRD, FT-IR, TEM, TGA/DTGA and pore structure analysis by N2 adsorption at −196°C was conducted. A higher degree of crystallinity and a larger specific surface area (SBET) were presented for ZL at aging temperature of 160 than at 140°C. Concurrently, a decrease in intensity of the diffraction line at d=3.342Ǻ due to α-quartz silica was seen, giving rise to an increase of the dissolution rate of silica component in the gel phase at 160 over 140°C. Complementary TEM and XRD techniques informed that the particle sizes measured 50 and 75nm for the former and latter, respectively. The ZL surface was modified with TPA+ (50–200mmol) and applied for chromate anions (5–30ppm) adsorption experiments in the aqueous solution at room temperature and pH 5. The capacity of chromate adsorption over ZL-modified TPA+ was greater by threefold than over ZL by the combination of electrostatic effects. The kinetics obeyed Freundlich model where the adsorption onto ZL-modified TPA+ affords 3.7mmol/g.