Silica bonded calix[4]arene as an efficient, selective and reusable sorbent for rubber chemical additives

This study presents the adsorption behavior of chemically bonded chlorosulfonyl-calix[4]arene to silica gel (CSC[4]A–SiO 2 ) for couples of rubber chemicals additives, diphenylguanidine (DPG), N -cyclohexyl-2-benzothiazolesulfenamide (CBS) and 2-mercaptobenzothiazole (MBT). Results of study showed that CSC[4]A–SiO 2 is a selective sorbent for DPG and CBS (as ordinary accelerators in the manufacture of rubber compounds) by means of electrostatic interaction and hydrogen bonding between hydroxyl groups of calix[4]arene moiety and the NH group of DPG and CBS molecules. The batch adsorption study was carried out to evaluate the rubber chemical additives removal efficiency and selectivity of CSC[4]A–SiO 2 . It was observed that the percentage of DPG and CBS removal reached 49 and 55% in the presence of CSC[4]A–SiO 2 respectively. In order to give evidence to the stronger interaction of DPG and CBS with CSC[4]A–SiO 2 , 1 H-NMR studies were performed. We have also discovered that the CSC[4]A–SiO2 can be act as a new auxiliary NMR shift reagent, via a host–guest molecular recognition process.