1 st International Conference Eco-Innovation in Science, Engineering, and Technology Volume 2020 http://dx.doi.org/10.11594/nstp.2020.0531 How to cite: Pangestu, M. A., Pracesa, Y. A. Y., & Perwitasari, D. S. (2020). Biosorption of total chrome metals on leather tannery liquid waste using tofu dregs. 1 st International Conference Eco-Innovation in Science, Engineering, and Technology. NST Proceedings. pages 200-204. doi: 10.11594/ nstp.2020.0531 Conference Paper Biosorption of Total Chrome Metals on Leather Tannery Liquid Waste Using Tofu Dregs Muhammad Aji Pangestu , Yahya Ardian Yuma Pracesa, Dyah Suci Perwitasari* Chemical Engineering Department, Faculty of Engineering, Universitas Pembangunan Nasional “Veteran” Surabaya, East Java, Indonesia *Corresponding author: ABSTRACT Chrome metal was the main element in tannery liquid waste. Chrome was included in B3 waste and has the potential to destructed or contaminated surroundings. The use of natural material as an adsorbent medium for b3 heavy metal currently was being studied. Tofu dregs were an alternative that can be used as biosorbent. This study's aim was to adsorbed total chrome metal in tannery liquid waste. The operating conditions took place at a pH of 7 and a stirring speed of 200 rpm. The analysis using Atomic Absorption Spectrometer (AAS) showed that the total chromium adsorption efficiency occurs in the addition of 6 grams of biosorbent with a contact time of 160 minutes. The adsorption percentage was 98% and the residual level total chromium metal in the tannery liquid waste was 0,33 mg/L after adsorption. These results have fulfilled the quality standard of the leather tannery wastewater that was allowed to be released into the environment with max- imum total chrome metal levels of 0,5 mg/L. The total chromium metal bio- sorption in this study followed the Langmuir isotherm and took place as chemisorption. Keywords: biosorption, isotherm Langmuir, total chrome, tofu dregs E-mail: saridyah052gmail.com Introduction The leather tanning industry is one of the industries that have a large amount of waste, namely in the form of solid, liquid, and gas. The waste comes from processed skin, materials for processing, and water. The waste from the skin is in the form of feathers, remains of meat, and pieces of skin, while the waste from processing materials is in the form of salt, lime, and other chemicals (Sugihartono, 2018). The wastewater from the leather tanning industry gen- erally contains chromium metal which comes from a tanning process using a chromium sulfate compound between 60-70%. However, in the tanning process, not all of the chromium sulfate solution is absorbed by the skin, so the rest is excreted in the form of liquid waste. The presence of high levels of chromium in the tannery liquid waste can cause environmental pollution and have a bad impact on health. Also, trivalent chrome waste will cause problems if it is oxidized to six valences (hexavalent) chromium ions which are toxic. (Ma'mun, et al 2016). There are several methods for removing heavy metal ions from solutions consisting of physi- cal, chemical, and biological methods. Conventional methods for removing toxic metal ions from solutions have been recommended, such as chemical precipitation, filtration, ion exchange, elec- trochemical treatment, membrane technology, coating, adsorption on activated carbon, evapora- tion, and photocatalysis (Gautam, et al 2014). Physical and chemical engineering requires high costs, a long process, and a lot of solvents so that it becomes a new problem in the exhaust system (Hevira, et al, 2019). One of the biological methods in dealing with heavy metal chromium is biosorption. According to Michalak and Katarzyna, Biosorption is an adsorption process that uses biological materials