The Utilization of Corn Stalks as Biochar to Adsorb BOD and COD in Hospital Wastewater Daud K. Walanda 1* , Alam Anshary 2 , Mery Napitupulu 1 , Ryka M. Walanda 3 1 Department of Chemistry, Tadulako University, Jl. Soekarno Hatta Km. 9, Palu, Central Sulawesi 94118, Indonesia 2 Department of Agrotechnology, Tadulako University, Jl. Soekarno Hatta Km. 9, Palu, Central Sulawesi 94118, Indonesia 3 Department of Biochemistry, Tadulako University, Jl. Soekarno Hatta Km. 9, Palu, Central Sulawesi 94118, Indonesia Corresponding Author Email: walanda@gmail.com https://doi.org/10.18280/ijdne.170114 ABSTRACT Received: 24 November 2021 Accepted: 14 January 2022 Biochar preparation from biomass and organic materials such as fruit peels, livestock manure, wood chips, and other agricultural residues has been studied. Those materials are prepared through a pyrolysis process, heating at a specific temperature, then utilized for adsorption waste pollution such as heavy metal ions. This study aimed to produce activated biochar from corn stalks (ABCS) as an adsorbent of BOD and COD in hospital wastewater. Activation of the biochar was carried out with an activator agent, namely ZnCl2. The moisture and ash content of activated biochar with a pyrolysis temperature of 400℃ and 500℃ meet SNI. SEM-EDS determined the pore and elements analysis. ABCS consist of 44.88 % and 60.56% of the carbon produced with different temperature of 400℃ and 500℃, respectively. One gram of ABCS reduced COD up to 71.4% in 4.5 hours and a maximum of 56.83% of BOD in 3 hours. While in an hour, a maximum of 2.5 g ABCS decreased COD 62.5% and 71.1% of BOD with the most of 1.5 g ABCS. Keywords: biochar, COD, BOD, SEM-EDS, corn stalks, adsorption, pyrolysis 1. INTRODUCTION Central Sulawesi is one of the centers of corn production in Indonesia, with total corn production in 2018 of 380.650 tons [1]. Waste from corn in the form of cobs, stems, husk, and leaves is the main source of biomass for the manufacture of activated carbon. Usually, these wastes have not been used properly and are only left to rot which can pollute the surrounding environment. Activated carbon is defined as pure charcoal that is chemically or physically treated to produce a micropore product, increasing its adsorptive surface area [2]. The large surface area (between 500 and 1500 m 2 /g) and the electric charge adsorb various polar compounds, mainly phenols, and derivatives [3]. Some research results on biochar derived from agricultural plant biomass, especially from fruit peels such as banana peels [4], cocoa [5], durian [6], salak fruit seeds [7], coconut husk [8], has been published in various reputable journals both nationally and internationally. Generally, the research carried out is applied as an adsorbent for metal ions such as Chromium, Cadmium, Lead, and others metals contained in the solution. These research experiences can be developed to increase biochar's capacity or adsorption capacity for mass production, which can improve water quality or wastewater treatment. Wastewater contains a lot of hazardous substances such as BOD and COD. Chemical oxygen demand (COD) is the amount of oxygen needed to oxidize organic waste in water through chemical reactions. Organic waste will be corrupted by potassium dichromate (K2Cr2O4) as a source of Oxygen into CO2 and H2O gas and some chromium ions. COD value is a measure of the level of pollution by organic matter. Biological Oxygen Demand (BOD) is the amount of Oxygen needed to overhaul organic matter in water by microorganisms at a specific temperature and volume. The greater the BOD value of water, the less oxygen is available to organisms in the water. BOD is closely related to DO (Dissolved Oxygen) or dissolved oxygen. The higher the BOD level of water, the less the amount of dissolved oxygen. So, the higher the BOD level, the higher the level of pollution [9]. Water treatment can be done physically by using a sand filter with a silica size adjusted to the size of the suspended materials to be filtered. Meanwhile, chemical wastewater treatment is usually carried out to remove non-precipitating particles (colloids), heavy metals, phosphorus compounds, and toxic organic substances by affixing certain required chemicals [10]. The removal of these materials in principle takes place through changes in the properties of these materials, namely from non-precipitation (flocculation-coagulation), either with or without an oxidation-reduction reaction, and also takes place as a result of an oxidation reaction [11]. Biological wastewater treatment is one of the treatment methods directed at reducing or eliminating specific substrates contained in wastewater by utilizing the activity of microorganisms to remodel the substrate. Physical water treatment with filter media, namely activated carbon, can reduce pollutant levels, namely BOD and COD in water. Activated charcoal is defined as a by-product obtained by the thermochemical conversion of biomass into heat, energy, fuel, and chemicals in a limited oxygen environment [8]. Activated biochar from corn stalks is made to be used to improve water quality by reducing BOD and COD levels in hospital wastewater. The utilization of corn stalks as materials for the manufacture of activated carbon strongly supports the zero- waste principle and prevents environmental damage due to waste. International Journal of Design & Nature and Ecodynamics Vol. 17, No. 1, February, 2022, pp. 113-118 Journal homepage: http://iieta.org/journals/ijdne 113