Insights into the mechanism of co-adsorption between tetracycline and nano-TiO2 on coconut shell porous biochar in binary system

The coexistence of nanoparticles (NPs) and environmental pollutants has become a new type of pollution, and the co-adsorption behaviors of coexisting NPs and pollutants on the coconut shell porous biochar is important to explore the environmental fate of both pollutants and NPs in complex environments. In this study, the interaction between nano-titanium dioxide (n-TiO2) and tetracycline (TC) during the adsorption process on the coconut shell biochar (CBC) was explored by adsorption experiment, the co-adsorption mechanisms of TC and n-TiO2 onto CBC were discussed by morphology and characteristics of Scanning electron microscopy, Brunauer-Emmett-Teller specific surface area, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The results showed that the n-TiO2 in the TC + TiO2 binary system leads to the TC adsorption decrease by 54.60% averagely. The TC in the TC + TiO2 binary system increased the n-TiO2 adsorption by 31.97% averagely but weakened the adsorption affinity of n-TiO2. Characterization analysis confirmed that, the hydrogen bonding, π-π/n-π interaction and pore filling between TC and CBC were suppressed in the TC + TiO2 binary system. The TC in the binary system enhances the n-TiO2 adsorption on the outer surface and the inner surface of CBC by surface bridging and reducing the agglomeration of n-TiO2.