Hydrophilic polythiophene/SiO ₂ composite for adsorption engineering: Green synthesis in aqueous medium and its synergistic and specific adsorption for heavy metals from wastewater

The design and synthesis of a selective and stable adsorbent for heavy metal ion adsorption is still challenging, as most adsorbents could not exhibit selectivity towards specific ion in the mixture ion solution, and the mechanism on the selective adsorption is still unknown. A design of polythiophene/SiO ₂ (PTh/SiO ₂ ) composite is a novel way to achieve the selective adsorption for the engineering application due to the synergetic effect between PTh and SiO ₂ . Unlike the traditional way to obtain a PTh which should be conducted in the organic solvent, the novel turbulent mixing applied in this study makes it possible to synthesize PTh in the aqueous medium, which is effective and environmental friendly. The self-doping interaction of SiO ₂ to the PTh was illuminated and characterized through various technical, which was suggested to lead to the high selectivity adsorption of the PTh/SiO ₂ . Through the description and prediction of pseudo-second order kinetic and Langmuir isothermal model, PTh/SiO ₂ composite exhibited a record impressive selectivity towards Zn ²⁺ in the multiple ion solution (with P value > 0.8 compared to 0.3 of Pb ²⁺ ), fast kinetics and excellent reusability, promising the composite to be an effective adsorbent applied to selectively separate and recycle Zn ²⁺ . Through several designed experiments such as PTh loading experiment and competitive adsorption, and various characterization including FTIR and UV–vis spectra study, the mechanism on the novel synergetic effect between the PTh and SiO ₂ was illuminated. SiO ₂ was confirmed to play an important role in the selective adsorption, while the integral affinity of the composite was improved by PTh. The mechanism proposed in this paper may create new composite building blocks to develop highly selective adsorption.