Removal of acid dyes from aqueous media by adsorption onto amino-functionalized nanoporous silica SBA-3

Adsorption of acid dyes on SBA-3 ordered mesoporous silica, ethylenediamine functionalized SBA-3 (SBA-3/EDA), aminopropyl functionalized SBA-3 (SBA-3/APTES) and pentaethylene hexamine functionalized SBA-3 (SBA-3/PEHA) materials has been studied. The structural order and textural properties of the synthesized materials have been studied by XRD, FT-IR and nitrogen adsorption–desorption analysis. The adsorption capacity of the adsorbents varies in the following order: SBA-3/PEHA > SBA-3/APTES > SBA-3/EDA > SBA-3. The SBA-3/PEHA is found to have the highest adsorption capacity for all acid dyes. The adsorption mechanism which is based on electrostatic attraction and hydrogen bonding is described. Batch studies were performed to study the effect of various experimental parameters such as chemical modification, contact time, initial concentration, adsorbent dose, agitation speed, solution pH and reaction temperature on the adsorption process. The Langmuir and Freundlich isotherm models have been applied and the Freundlich model was found to be fit with the equilibrium isotherm data. Kinetics of adsorption follows the second-order rate equation.

Synthesis of mesoporous silica SBA-3 and PEHA (pentaethylene hexamine) was used as agent to modify SBA-3 and main interactions between acid green 28 and SBA-3/PEHA.Figure optionsDownload as PowerPoint slideHighlights
► Various amine functional groups have been studied for functionalization of the SBA-3.
► The pentaethylene hexamine functionalized SBA-3 possessed a higher adsorption capacity.
► The electrostatic attraction and hydrogen bonding were the main mechanisms.