Synthesis of nano sized 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

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 (Z(L)) and its respective synthesized with most common tetrapropyl-ammonium bromide (TPABr) (Z(T)) using XRD, FT-IR, TEM, TGA/DTGA and pore structure analysis by N-2 adsorption at -196 degrees C was conducted. A higher degree of crystallinity and a larger specific surface area (S-BET) were presented for Z(L) at aging temperature of 160 than at 140 degrees C. Concurrently, a decrease in intensity of the diffraction line at d = 3.342 angstrom due to alpha-quartz silica was seen, giving rise to an increase of the dissolution rate of silica component in the gel phase at 160 over 140 degrees C. Complementary TEM and XRD techniques informed that the particle sizes measured 50 and 75 nm for the former and latter, respectively. The Z(L) surface was modified with TPA(+) (50-200 mmol) and applied for chromate anions (5-30 ppm) adsorption experiments in the aqueous solution at room temperature and pH 5. The capacity of chromate adsorption over Z(L)-modified TPA(+) was greater by threefold than over Z(L) by the combination of electrostatic effects. The kinetics obeyed Freundlich model where the adsorption onto Z(L)-modified TPA(+) affords 3.7 mmol/g. (C) 2012 Elsevier Inc. All rights reserved.