Adsorptive removal of chromium (VI) ions from solution using P-doped nanostructured carbon materials: Modelling of the adsorption isotherms, Thermodynamics and Kinetic investigation

Document Type : Regular Articles

Authors

1 assistant researcher at Agricultural Research Center

2 Chemistry Department, Faculty of Science, Sohag University

3 Senior Researcher at Environment Department Soils, Water and Environment Research Institute Agricultural Research Centre

10.21608/sjsci.2025.409045.1301

Abstract

A series of nanostructured phosphorous P-doped porous carbons synthesized from sorghum stalks biomass were investigated for Cr (VI) adsorptive removal. The adsorbent materials, which were activated at 400, 600 and 800 °C, are characterized by ultra-high surface area (SBET), mesoporous surface area (Smeso) and graphene-like structure with slit shaped porosity. The adsorbents showed adsorption capacity, (qads) in the order of SCP600 > SCP800 > SCP400, which was the same order for total pore volume (VT), and pore width (PW). The most active adsorbent, SCP600, showed qads of 120.1 mg/g at pH of 2. Modeling of the adsorption isotherms were investigated by a group of related isotherms, which showed the best fit with the Langmuir isotherm model. Kinetic of the adsorption process was investigated via three kinetic models and showed to follow the pseudo-second order model. Thermodynamic studies at different initial Cr (VI) concentrations resulted in negative ΔH°, ΔS°, and ΔG° values. Thus, indicating physicochemical and spontaneous adsorption. The present investigation emphasizes that qads, of P-doped porous carbon materials derived from sorghum stalks towards Cr (VI) is related not only to SBET and Smeso but also to the VT and Pw SCP of the adsorbent materials. 

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