Hydrothermal carbonization of glucose in saline solution: sequestration of nutrients on carbonaceous materials

In this study, feasibility of selected nutrient sequestration during hydrothermal carbonization (HTC) was tested for three different HTC temperatures (180, 230, and 300 degrees C). To study the nutrient sequestration in solid from liquid solution, sugar and salt solutions were chosen as HTC feedstock. Glucose was used as carbohydrate source and various salts e.g., ammonium hydrophosphate, potassium chloride, potassium sulfate, and anhydrous ferric chloride were used as source of nitrogen and phosphorus, potassium, and iron, respectively. Solid hydrochar was extensively characterized by means of elemental, ICP-OES, SEM-EDX, surface area, pore volume and size, and ATR-FTIR to determine nutrients' sequestration as well as hydrochar quality variation with HTC temperatures. The spherical mesoporous hydrochars produced during HTC have low surface area in the range of 1.0-3.5 m(2) g(-1). Hydrochar yield was increased about 10% with the increase of temperature from 180 degrees C to 300 degrees C. Nutrient sequestration was also increased with HTC temperature. In fact, around 71, 31, and 23 wt% nitrogen, iron, and phosphorus were sequestered at 300 degrees C, respectively. Potassium sequestration was very low throughout the HTC and maximum 5.2% was observed in solid during HTC.