Comparative Studies of Titanium Silicate as Heavy Metal Removal Adsorbent Synthesized through Conventional and Hybrid Surfactant Template Techniques

Titanium silicate-1 (TS-1) has attracted much attention during the last decade because of its interesting catalytic and adsorption properties. Most of TS-1 synthesis methods require the use of a comparatively copious amount of a costly template such as tetra propyl ammonium hydroxide (TPAOH). Thus, an attempt to reduce the cost of TS-1 synthesis by an alternatively or at least lessen the concentration of TPAOH. Two reactants to precipitate TS in the template involving tetra-n-butyl titanate (TNBT) as titanium source and tetra ethyl ortho silicate (TEOS) as silica source were used as precursors. The results were compared with the TS sample prepared without sodium dodecyl sulphate (SDS) and with sample prepared with different Si/Ti ratios. Si/Ti ratio of 33:1 was chosen to prepare titanosilicate (TS) samples synthesized by the conventional method using TPAOH as surfactant and TS samples synthesized using SDS and TPAOH as hybrid surfactant. Characterization of TS samples has been achieved by using a Fourier transform infra-red (FTIR) spectroscope, x-ray diffraction (XRD) and scanning electron microscope (SEM) to show the degree of crystallinality, while UV-VISIBLE spectroscopy was used to confirm whether the Ti present in the TS is in the tetrahedral position or in the form of extra framework. It shows the presence of the characteristic band for TS at 960cm-1, confirming Si-O-Ti linkages present in all samples. Surface area and pore size distribution of TS samples were measured by nitrogen adsorption analysis. It was revealed that all TS produced by hybrid surfactant generated a higher surface area compared to conventional method. The nitrogen adsorption analysis shows that TS-hybrid synthesized using a mild condition ie. crystallized at room temperature and atmosphere pressure possesses a bimodal with fairly narrow pore size distribution. Batch experiment investigations utilizing Cu(II) and Pb(II) ions were conducted to examine the heavy metal removal capabilities of TS. The results showed that almost all of the TS produced by hybrid surfactant generated a higher metal ions uptake Qt, compared to conventional method. TS tempalated using hybrid surfactant offers a less costlier and less time-consuming route compared conventional methods.