Waste-to-Resource Approach: Fabrication of a Sustainable Phosphate Adsorbent from Soybean Hull Residues and Dolomite
Dina Wahyu Indriani1,2, Stella Jovita1, Riki Subagio1, Holilah Holilah3, Yatim Lailun Ni^mah1,*, Didik Prasetyoko1

1Department of Chemistry, Faculty of Science and Data Analytics, Institute Technology Sepuluh Nopember (ITS), Sukolilo, Surabaya 60111, Indonesia
2Department of Biosystem Engineering, Faculty of Agricultural Technology, Universitas Brawijaya, Jalan Veteran Malang, 65144 Indonesia
3Research Center for Biomass and Bioproducts, National Research and Innovation Agency of Indonesia (BRIN), Cibinong 16911, Indonesia

*Email: nikmah[at]chem.its.ac.id

Abstract

Phosphate pollution in aquatic ecosystems, primarily due to agricultural and industrial wastewater, has raised serious environmental concerns, including eutrophication and the depletion of non renewable phosphate rock reserves. In response, this study presents a waste to resource approach by repurposing soybean hull residues and dolomite to fabricate a sustainable biochar based composite for phosphate adsorption. The composites were synthesized via pyrolysis at varying temperatures (400, 600, and 800 C), which significantly influenced their physicochemical properties and adsorption behaviours. Characterization revealed that pyrolysis at 800 C yielded the highest phosphate adsorption capacity, attributed to the formation of Calcium carbonate and Magnesium oxide phases that enhance phosphate binding. The adsorption performance followed the Langmuir isotherm model and pseudo second order kinetics, indicating that monolayer chemisorption is the dominant mechanism. The composite exhibited high structural stability post-adsorption, suggesting its reusability and practical applicability. This study contributes to the development of low-cost, eco-friendly adsorbents from agricultural and mineral waste for sustainable phosphate recovery and water purification

Keywords: Dolomite- Phosphate adsorption- Soybean hull- Sustainable water treatment

Topic: Waste and environmental management and engineering