A novel nanocomposite as adsorbent for formaldehyde removal from aqueous solution

In order to develop a new adsorbent for removal of formaldehyde from aqueous solution, surface modification of TiO2 nanoparticles was performed with 2,4-Dinitrophenylhydrazine (DNPH) that have a strong affinity to the formaldehyde. Sodium dodecyl sulfate (SDS) surfactant was used to improve the DNPH grafting to TiO2 surface. Modified adsorbents were characterized by SEM, TEM, XRD, EDX and FTIR. Since the COD level in wastewaters including formaldehyde is considerable, it is necessary to determine the COD content of the synthetic wastewater. In order to determine the optimal removal conditions, the effect of contact time (60-210 min), pH (4-10) and adsorbent dosage (0.5-1.5 g/L) on adsorption and COD removal efficiencies were studied, using response surface method. EDX and FTIR analysis confirmed the presence of nitrogen-containing functional groups on the modified TiO2 surface. The maximum formaldehyde adsorption and COD removal efficiencies by modified TiO2 were about 15.65 and 7.35% higher than the unmodified nanoparticles respectively. Therefore, the grafting of nano-TiO2 with DNPH would greatly improve its formaldehyde adsorption efficiency. The optimum conditions determined for a maximum formaldehyde removal of 99.904% and a COD reduction of 94.815% by TiO2/SDS/DNPH nanocomposites were: adsorbent dosage 1.100 g/L, pH 7.424 and the contact time 183.290 min.