Cetyl Trimethyl Ammonium Bromide (CTAB) functionalized sodium silicate for Naphtol Green B and Congo Red adsorption.

Abstract Removal of dyes using optimized and renewable adsorbent with high adsorption capacity remain a challenge. Rice husk was used as a raw material for the manufacture of a new CTAB-functionalized sodium silicate adsorbent. The adsorption capacity of raw rice husk, calcined rice husk (400, 600, 800, and 1000°C), and functionalized sodium silicate with CTAB (Cetyl Trimethyl Ammonium Bromide) was investigated. SEM, FTIR, TGA-DSC and zeta potential characterized the modified rice husks. Adsorption tests were carried out using Naphthol Green B (NGB) and Congo Red (CR) as dyes. Results showed that the calcination temperature influenced the sodium silicate adsorption capacity and enhanced the effect of functionalization by CTAB at 600°C as the optimum calcination temperature. The maximum adsorption capacities of CR and NGB were 73.04 and 86.59 mg g-1, respectively, which were higher than those generally observed in the literature. The optimal adsorption condition was pH of 6, 0.1 g of Na2SiO3-CTAB, 30 min of contact time, and 303K. The desorption using a 50% acetone solution of 0.1g Na2SiO3-CTAB showed a desorption capacity of 96.21 % and 92.32 %, respectively, for CR and NGB. Desorption results show that a combination of hydrogen bonds and Van Der Walls interactions occurred. Four cycles of adsorption/desorption were done, and the desorption rate decreased to 42.23% and 13.93% for CR and NGB, respectively. Thus, it can be concluded that sodium silicate modified with CTAB after calcination at 600°C is a potential low-cost adsorbent and renewable sorbent for the removal of dyes from industrial wastewater.