Co-hydrothermal carbonization of rape straw and industrial sewage sludge – applications of hydrochar for N and P adsorptions and for agricultural/horticultural purposes

Reuse of agricultural and industrial wastes simultaneously to prepare hydrochars (HCs) for removal of NH4+ and PO43- in practical sewage without additional wastes produced is still a challenge. Herein, HCs were fabricated by combination of rape straw and industrial sewage sludge to remove NH4+ and PO43- from hoggery effluent. Synthesis conditions were firstly optimized and optimized HC (OPT-HC) was further applied to adsorb NH4+ and PO43-. Monolayer and Pseudo-first-order as well as Pseudo-second-orders were confirmed via adsorption kinetic and isothermal adsorption studies. Morphologies and surface areas of the OPT-HC did not show any transformations before and after adsorption of NH4+ and PO43-. The OPT-HC after adsorption of NH4+ and PO43- (OPT-HC-N/P) was further applied as fertilizer for planting Ping-pong Chrysanthemum. Results indicate that the OPT-HC-N/P can improve comprehensive qualities of the Ping-pong Chrysanthemum such as plant height, fresh, Vitamin C, Chlorophyll, soluble protein and sugar because the OPT-HC-N/P can provide extra N and P elements and also promote to release available K in soil. OPT-HC-N/P treated Ping-pong Chrysanthemum open flowers in advance. Thus, two kinds of wastes were re-utilized to remove N and P in real-life effluent.