(199f) Investigating the Sorption Capacity of Hydrochar for Organic Pollutants and Comparing with That of Powdered Activated Carbon (PAC) As a Method of Treating Contaminated Water

Water is perhaps the most critical component of our diets. Water is plentiful on earth, but obtaining clean potable water for human consumption is a big challenge in many parts of the world. Water is contaminated by organic compounds coming from industrial waste (e.g. pharmaceutical chemicals) and from agricultural water run offs (e.g. pesticides, herbicides, chemical fertilizers). These chemicals have deadly effects on human bodies if consumed in the amount exceeding the safe-level limits. One of the most common methods of removing organic pollutants is adsorption, a phenomenon in which absorbable solute (adsorbate) is chemically or physically attached to a solid with highly porous surface structure (adsorbent).

Due to its high level of microporosity which leads to high surface area (> 800 m²/g), powdered activated carbon (PAC) is the most common adsorbent being employed to remove organic chemicals from water. PAC is usually produced from carbonaceous (biomass) sources via dry pyrolysis. The shortcoming of this process is the requirement for the biomass feedstock to have extremely low moisture content. Drying biomass materials requires a large amount of energy, especially if the materials contain high moisture content.

This study aims to evaluate the potential of hydrochar as a low-cost sorption agent. Hydrochar is solid carbon material produced from a thermochemical process, namely hydrothermal carbonization (HTC), in which wet organic materials (e.g. food wastes) are immersed in water and heated to temperature between 180 and 270^oC under sub-critical condition during which water remains in liquid phase. The absence of liquid-to-vapor phase change of water makes the HTC process less energy intensive compared to the process of producing PAC which involves water vaporization and high-temperature carbon activation.

It has been reported that, similar to commercial PAC, hydrochar produced from HTC process also displays high level of microporosity. This property brings up the question whether, like commercial PAC, hydrochar will have the high sorption capacity and potential to become a low-cost sorption agent. Since it can be created by common organic materials like food wastes, hydrochar can be produced anywhere using local organic resources, even in rural and developing communities. Another advantage of hydrochar production is the reduction of organic wastes flowing to landfills, thus reducing the potential synthesis of greenhouse gases⁴.

In this sorption study, a large variety of hydrochar materials are evaluated for their sorption capacities. The hydrochars were made from different types of food waste (carbohydrates, vegetables, plant proteins and animal proteins) at various HTC process temperatures and retention times. The hydrochars are tested for adsorbing three different common organic pollutants, namely 2,4 Dichlorophenol (2,4 DCP), acetaminophen, and Bentazon 4 herbicide. To be reported are the effects of types of food feedstock and the HTC process conditions (temperatures and reaction time) on the sorption capacities of hydrochars for the three organic pollutants tested along with the comparison of hydrochar sorption capacities with respect to that of the commercial PAC.

*Contact: Dr. Justinus Satrio (justinus.satrio@villanova.edu)