Kinetic Modeling of Humic Acid Production from Oxidized South Sumatera Lignite Toward Green and Sustainable Synthesis

Document Type : Original Article

Authors

1 Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Sleman, Indonesia

2 Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Sleman, Indonesia

3 Graduate School of Engineering, Hokkaido University, Sapporo, Japan

4 Chemical Engineering Department, Universitas Gadjah Mada, Jalan Grafika 2 Yogyakarta 55281, Indonesia

5 Chemical Engineering Department, Faculty of Industrial Engineering, Universitas Pembangunan Nasional “Veteran” Yogyakarta, Sleman, Indonesia

6 Research Department, PT. Pupuk Sriwidjaja Palembang, Palembang, Indonesia

Abstract

This study investigates the reaction kinetics of hydrogen peroxide (H2O2) oxidation of low-rank coal (lignite) to produce humic acid. Utilizing H2O2 as a green oxidant enhances the environmental compatibility of the process, aligning with Sustainable Development Goals of responsible consumption and production. Scaling up laboratory processes requires practical insights into kinetic parameters that are essential for designing process equipment. The oxidation of coal with H2O2 is solid-liquid reaction, typically governed by three steps to control the process: diffusion through a thin film layer, diffusion through the solid state, and chemical reaction. Despite its potential, research on the kinetics of chemical oxidation in lignite remains relatively limited. In this study, coal particles (-60 +80 mesh) are oxidized using 10% H2O2. At specific time intervals, a certain volume of the solution is taken and measured through titration. The evaluation of kinetic models involves liquid film diffusion (sphere), Jander diffusion (three dimensional), ash diffusion, first order, second order, and surface reaction. The result shows that the oxidized coal demonstrates the addition of carboxyl groups. The kinetics model highlights the surface reaction as the controlling process. The estimated activation energy stands at 29.80 kJ/mol, with an Arrhenius constant of 121.10 min-1. This study suggests the possibility of conducting the reaction at room temperature.

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Egyptian Journal of Chemistry
Volume 68, Issue 13 - Serial Number 13
(In Loving Memory of Late Professor Doctor”Zeinab M. Nofal” In progress
December 2025
Pages 757-764

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History

  • Receive Date: 07 February 2025
  • Revise Date: 07 June 2025
  • Accept Date: 22 June 2025

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