Hydrothermal carbonization of vegetable-tanned leather shavings (HTC-VTS) for environmental remediation: optimization of process conditions

Herein, the response surface methodology (RSM) has been used to study simultaneously the effects of carbonization temperature, residence time, and moisture content on the activated hydrochar preparation-based vegetable-tanned leather shavings (VTS) using hydrothermal carbonization method (HTC). Owing to the desirability chosen, three responses were analysed, namely: the hydrochar yield, iodine, and methylene blue numbers. The analysis of experimental results revealed that the hydrochar yield was decreased with an increase in carbonization temperature which led to micropores formation inside the hydrochar network. The optimal preparation conditions retained were: 83.10%, 390.44 mg/g, and 259.63 mg/g for the hydrochar yield, iodine, and methylene blue number respectively. The hydrochar micrograph showed the presence of external pores, whereas the FTIR analysis recorded the presence of acidic functional groups found on hydrochar surface. The findings revealed that the VTS is a good precursor for the hydrochar preparation useful in the removal of organic and inorganic pollutants in aqueous media. 

Methods
FTIR Analysis, SEM (Scanning Electron Microscopy), BET (Brunauer-Emmett-Teller)_VTS_HTC (Vegetal Tanned Shaved-Hydrothermal Carbonization), and TGA (Thermogravimetric analysis)