Adsorbent Materials for Hydrocarbons Removal by Geopolymerization of Halloysite Clay Nanotubes Filled Within Chitosan Matrix

We propose a protocol for the fabrication of hybrid materials with high adsorption capacity toward aliphatic and aromatic hydrocarbons by alkaline activation of halloysite clay nanotubes filled within a chitosan matrix. First, chitosan/halloysite nanocomposite films with variable composition have been prepared by aqueous casting method. Interestingly, the films have exhibited compactness and robustness although the large halloysite contents (≥30 wt.%) as demonstrated by the elastic modulus and the tensile strength values, which range between 1635–4475 MPa and 5.46–26.5 MPa, respectively. The mesoscopic properties (thermal stability, wettability, and tensile resistance) of the chitosan/halloysite films have been correlated with their morphologies. Then, the chitosan/halloysite films have been immersed in NaOH solution to achieve the alkaline activation of the clay nanotubes. Their successful conversion to geopolymeric materials has been proved by thermogravimetric analysis and FTIR/Raman spectroscopies. Finally, we have investigated the adsorption capacities of chitosan/halloysite (50:50) composite (before and after geopolymerization) toward dodecane vapors and phenol dispersed in water. The geopolymerization process has enhanced hydrocarbon removal by ca. 220% and ca. 50% for dodecane and phenol, respectively. This work highlights that chitosan/halloysite composite films can be easily converted to porous geopolymers suitable for decontamination purposes in vapor and aqueous phases.