Clean Water and Sanitation (SDG 6), Climate Action (SDG 13)
Response surface methodology directed modelling of the biosorption of progesterone onto acid activated Moringa oleifera seed biomass: parameters and mechanisms Emily Ngeno a,b,c , Roselyn Ongulu a , Victor Shikuku b , Deo Ssentongo c , Benton Otieno d , Patrick Ssebugere c,e,f,* , Francis Orata a a Department of Pure and Applied Chemistry, Masinde Muliro University of Science and Technology, P.O Box 190–50100, Kakamega, Kenya. b Department of Physical Sciences, Kaimosi Friends University, P.O Box 385–50309, Kaimosi, Kenya. c Department of Chemistry, Makerere University, P. O Box 7062, Kampala, Uganda. d Department of Chemical and Metallurgical Engineering, Vaal University of Technology, Vanderbijlpark, South Africa. e Department of Cell Toxicology, Helmholtz Centre for Environmental Research UFZ, 04318, Leipzig, Germany. f Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research UFZ, 04318, Leipzig, Germany. Corresponding author at: Department of Chemistry, Makerere University, P. O Box, 7062, Kampala, Uganda: patrick.ssebugere@mak.ac.ug (P. Ssebugere). In this study, chemically activated fat-free powdered Moringa oleifera seed biomass ( MOSB ) was synthesized, characterized, and utilized as a cost-effective biosorbent for the abstraction of progesterone (PGT) hormone, an endocrine disrupting chemical (EDC), from synthetic wastewater. The process variables including temperature, pH, contact time, adsorbate concentration, and adsorbent dosage were optimized using response surface methodology (RSM) to obtain the greatest efficacy of MOSB during biosorption of PGT. The optimum parameters for PGT adsorption onto MOSB were: 86.8 min, 500 µg L -1 adsorbate concentration, 298 K, and 0.1 g adsorbent dosage. PGT removal from aqueous solutions was pH-independent. The Langmuir isotherm best fitted the equilibrium data with maximal monolayer adsorption capacity of 135.8 µg g -1 . The adsorption rate followed the pseudo-first-order (PFO) kinetic law. The thermodynamics functions (ΔG < 0, ΔH = -9.258 kJ/mol and ΔS = +44.16 J/mol) confirmed that the biosorption of PGT onto MOSB is a spontaneous and exothermic process with increased randomness at the adsorbent surface. The biosorption mechanism was physisorption and was devoid of electrostatic interactions. The findings from this study indicate that MOSB is a promising candidate for an inexpensive, low-carbon and environmentally friendly biosorbent that can effectively scavenge PGT from aqueous solutions. Key words: Moringa oleifera seed biomass ( MOSB ); Progesterone; acid-activation; biosorption
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