Activation of hydrochar derived from food waste via hydrothermal carbonization for Cu(II) adsorption

Currently, heavy metal pollution is a challenge that needs to be solved urgently, and there is a broad prospect for food waste(FW) utilization. In this paper, activated hydrochar (AHC) made from FW according to actual proportion was produced by hydrothermal carbonization (HTC) and activated with K₂CO₃. The effects of the AHC on Cu(II) adsorption were investigated using static adsorption experiments. The results indicated that the sample fabricated at 160°C (FW-160) for 6 h had the best adsorption performance with the maximum adsorption amount of Cu(II) (36.77 mg/g). The oxygenated functional group on the surface of FW-160 was observed. The pseudo-second-order kinetic model fitted the experimental results better, which proved that chemisorption was the main adsorption mechanism, and the surface complexations, including oxygenated functional groups, were the predominant factors in hydrochar(HC) sorption for Cu(II). The adsorption amount of the sample simulating rotten FW with Aspergillus niger (FW-160A) was 24.82 mg/g. Through the HTC process, the rotten FW can be made into heavy metal absorbents which can be stored for long term, and finally realize the reduction of volume and cost of storage.