Optimized synthesis of Cu2+-modified Samanea saman-derived carbon adsorbent for metformin adsorption

Malays. J. Anal. Sci. Volume 30 Number 2 (2026): 1649

Research Article

Optimized synthesis of Cu²⁺-modified Samanea saman-derived carbon adsorbent for metformin adsorption

Mohd Raziff Mat Hasan, Erniza Mohd Johan Jaya, and Mohd Azmier Ahmad^*

School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia

^*Corresponding author: chazmier@usm.my

Received: 6 August 2025; Revised: 21 January 2026; Accepted: 1 March 2026; Published: 28 April 2026

This study explores the efficacy of copper-modified carbon adsorbent derived from Samanea saman (Cu²⁺-SSCA) for the removal of metformin (MET), a commonly detected pharmaceutical pollutant, from aqueous environments. The pristine SSCA was synthesized through pyrolysis of the precursor under nitrogen (N₂), followed by CO₂ activation in a vertical furnace. Subsequent surface modification was achieved via impregnation with copper (II) nitrate [Cu(NO₃)₂], yielding the Cu²⁺-SSCA. The resulting material demonstrated a Brunauer–Emmett–Teller surface area (S.A._BET) of 748.66 m²/g, a mesoporous surface area (S.A._MESO) of 548.74 m²/g, total pore volume (T.P.V.) of 0.3051 cm³/g, followed by an average pore diameter (A.P.D.) of 2.41 nm, characteristics indicative of a well-developed mesoporous network. Process optimization using response surface methodology (RSM) identified optimum conditions at an activation temperature of 579 °C, followed by activation time of 1.20 h, and lastly, a Cu²⁺ ion impregnation ratio (IR) of 0.50 g/g. Under these conditions, the model-predicted MET adsorption capacity and Cu²⁺-SSCA yield were 67.63 mg/g and 32.81%, respectively, in close agreement with experimental results of 68.90 mg/g (error of 1.84%) and 34.00% (error of 3.50%). Isotherm modelling revealed that MET adsorption adhered to the Langmuir model, exhibiting a Langmuir capacity (Qₘ) of 109.27 mg/g. The Freundlich heterogeneity index (n_F) of 1.71 further confirmed favourable adsorption behaviour. In terms of kinetic study, the adsorption system followed pseudo-first order (PFO) the best.

Keywords: adsorption, surface modification, activated carbon, optimization, isotherm

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