BSTR, 2023, Vol 11, No 1, 33-43 https://doi.org/10.54987/bstr.v11i1.834 - 33 - This work is licensed under the terms of the Creative Commons Attribution (CC BY) (http://creativecommons.org/licenses/by/4.0/). Isothermal Remodelling of the Biosorption of Congo Red onto Kaolin Faggo Abdullahi Adamu 1,2 , Ain Aqilah Basirun 1 , Ahmad Syazwan Ismail 1 , Mohd Ezuan Khayat 1 and Mohd Yunus Shukor 1 * 1 Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. 2 Department of Microbiology, Faculty of Science, Bauchi State University Gadau, Bauchi, PMB 065, Nigeria. *Corresponding author: Mohd Yunus Shukor, Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. Email: mohdyunus@upm.edu.my INTRODUCTION The world is facing a great challenge in ensuring widespread access to clean and safe drinking water. Water pollution occurs when environmental stressors are introduced at concentrations exceeding the maximum permissible levels, rendering water unsuitable for consumption and various other purposes. Such pollution stems from the presence of organic and/or inorganic chemicals, minerals, or waste materials originating from diverse sources, including industrial, agricultural, clinical, and domestic activities [1–5]. Of these sources, industrial effluents emerge as the most significant contributors to the contamination of surface and groundwater. This phenomenon is exacerbated by the rapid process of globalization and urbanization, which fuels the demand for products manufactured using dyes and heavy metals [6–11]. Notably, heavy metals like copper (Cu) and lead (Pb) are commonly found in the wastewater of industries situated in smelting, electrical, and mining areas[12–14]. Meanwhile, dyes and pigments are prevalent in the effluents of sectors such as food, textiles, and pharmaceuticals, where these substances are employed as colorants. It is crucial to highlight the carcinogenic and mutagenic properties of these non-biodegradable and highly toxic chemicals [15–19]. Dyes, broadly categorized into various types, are essential in industries like textiles, with approximately 8 × 10 5 tons of synthetic dyes produced annually [15,20,21]. The textile sector alone accounts for roughly 75% of the global dyestuff market, employing a wide array of dyes for fabric coloring and printing . However, excessive dye usage can lead to poor fixation on HISTORY Received: 12 th April 2023 Received in revised form: 24 th June 2023 Accepted: 28 th June 2023 ABSTRACT A remodeling analysis was conducted on the sorption isotherm data for Congo Red adsorption onto kaolin using nonlinear regression. (CR) also known as 1-naphthalenesulfonic acid, 3,3′- (4,4′-biphenylenebis(azo)) bis(4-amino-) disodium salt, is a synthetic anionic azo dye widely utilized in various industrial sectors, including rubber, plastic, textiles, paper, and printing. This dye is of significant interest due to its versatile applications and unique chemical properties. To prevent overfitting due to the limited data points, isotherm models with up to three parameters were utilized. Statistical analysis based on error function assessments, including root-mean- square error (RMSE), adjusted coefficient of determination (adjR 2 ), accuracy factor (AF), bias factor (BF), Bayesian Information Criterion (BIC), corrected AICc (Akaike Information Criterion), and Hannan-Quinn Criterion (HQC), revealed that the best performance was achieved by the Freundlich model, followed by the Langmuir and Jovanovic models, which ranked as the top three models.The best isotherm model was found to be the Unilan followed by (descending order) Brouers–Sotolongo, Hill, Sips and Langmuir. The Unilan maximum adsorption capacity, shows large deviation from the experimentally observed value with a large 95% confidence interval, indicating poor fitting parameters despite being the best model based on the error function analysis. The next best model was Brouers–Sotolongo with a maximum adsorption capacity, qmBS of 5.48 mg g -1 (95% confidence interval from 4.791 to 6.172) which agrees with experimental observations. The value of the maximum monolayer adsorption capacity for Congo Red binding to kaolin according to the Langmuir’s parameter qmL was 5.49 mg g -1 (95% Confidence interval from 5.018 to 5.967), while bL (L mg -1 ), the Langmuir model constants was 0.5 L mg -1 (95% C.I. from 0.285 to 0.710). KEYWORDS Congo Red Adsorption Kaolinite Freundlich Langmuir BIOREMEDIATION SCIENCE AND TECHNOLOGY RESEARCH Website: http://journal.hibiscuspublisher.com/index.php/BSTR/index BSTR VOL 11 NO 1 2023 SEM of D. antarctica