Fabrication of robust and compressive chitin and graphene oxide sponges for removal of microplastics with different functional groups

Microplastics (MPs), an emerging threat to terrestrial ecosystems, have aroused global concerns due to the potential harm to wildlife and human. So far, no effectively method has been found to remove MPs from wastewater. In the present study, a robust and compressive sponge prepared from chitin and graphene oxide (ChGO) was achieved with the compressive stress of 50 and 40 MPa at dry and wet status. Such sponge efficiently adsorbed different types of MPs from water at pH 6-8 and can be reusable with the high adsorption capacity of 89.8%, 72.4%, and 88.9% for neat polystyrene, carboxylate-modified polystyrene, and aminemodified polystyrene, respectively, even after three adsorption-desorption cycles. The adsorption kinetic study suggested that the electrostatic interactions, hydrogen bond interactions, and pi - pi interactions were the main driving force for MPs absorption and the intra-particle diffusion played a major role in the whole adsorption process. The isotherm results followed the Langmuir isotherm model with the maximum adsorption capacity of PS calculated to be 5.898. 7.528, and 8.461 mg g(-1) at 25, 35, and 45 degrees C, respectively. In addition, the sponge did not inhibit the microalga growth using the Chromochloris zofingiensis model, and could be biodegraded by microorganisms in soil. The present study has provided a new approach for efficient MPs removal from water by using robust and compressive sponges from renewable biomaterials. Due to their excellent reusability, biocompatibility and biodegradability, such sponge has potential application in treating MPs pollution from water.