Hydrothermal conversion of lignocellulosic waste to value-added biomaterial for high-performance contaminant removal: Focusing on synthesis route and uptake mechanism

In this paper, a novel carbonaceous material was successfully synthesized from lignocellulosic waste by a green conversion technology. Pomegranate (Punica granatum L.) pulp waste (PPW) was transformed to hydrochar (PPWHC) through hydrothermal carbonization (HTC) and the key affecting factors including the holding temperature (HT; 180-220 C) and holding time (Ht; 6-24 h) were explored. The physico-chemical, structural, functional, morphological properties were discussed by C-13 NMR, BET, XRD, XPS, SEM/EDX, FT-IR, Raman, and CHNS elemental analysis. Based on the carbon content, higher heating value and energy densification values, a HT of 220 C and Ht of 12 h were determined as optimal operational conditions. Further, PPWHC was utilized for the removal of Rhodamine B (RhB) in batch mode. The maximum uptake was 121.95 mg/g at 323 K. Adsorption thermodynamics parameters were calculated. Additionally, reusability studies demonstrated that PPWHC exhibited a superior removal performance for RhB after five consecutive sorption/desorption cycles.