Mathematical Modelling and Optimization for Facile Synthesis of Structured Activated Carbon (ACs) from Adansonia kilima (Baobab) Wood Chips Integrating Microwave-Assisted Pyrolysis for the Elimination of Lead (II) Cations from Wastewater Effluents

Abstract

In this research, activated carbon (AC) was synthesized from ligno-cellulosic residues of Adansonia kilima (Baobab) wood chips (AKTW) using two-step semi-carbonization and subsequent pyrolysis using microwave-induced heating (MWP) in the presence of a mild activating agent of K2CO3. The influence of process input variables of microwave power (x1), residence time (y1), and amount of K2CO3 (z1) were analysed to yield superior quality carbon having maximum removal efficiencies (R1) for lead (II) cations from waste effluents, fixed carbon percentages (R2), and carbon yield percentages (R3). Analysis of variance (ANOVA) was used to develop relevant mathematical models, with an appropriate statistical assessment of errors. Level factorial response surface methodology (RSM) relying on the Box–Behnken design (BBD) was implemented for the experimental design. The surface area and porous texture of the samples were determined using Brunauer, Emmett, and Teller (BET) adsorption/desorption curves based on the N2 isotherm. Surface morphological structure was observed using field emission scanning electron microscopic (FESEM) analysis. Thermogravimetric analysis (TGA) was carried out to observe the thermal stability of the sample. Change in the carbon content of the samples was determined using ultimate analysis. X-ray diffraction (XRD) analysis was performed to observe the crystalline and amorphous texture of the samples. The retention of a higher proportion of fixed carbon (80.01%) ensures that the synthesized adsorbent (AKTWAC) will have a greater adsorption capacity while avoiding unwanted catalytic activity for our synthesized final sample.

Two step synthesis and application of porous carbon for removal of copper (II) from wastewater: Statistical optimization and equilibrium isotherm analysis

“…For fixed carbon content percentages, β3; temperature (𝐴 1 ), time (𝐵 1 ), and ratio (𝐶 1 ) were significant model terms (Table 5). The obtained standard deviations (SD%) and coefficient of variation (CV) were minimal, implying that the suggested models are dependable (Tables 3, 4, and 5) (Sellamuthu et al 2023). The signal/noise ratio (s/n) achieved in this case exceeded 4, indicating sufficient precision for the proposed models (Sellamuthu et al 2023) The impact of processing variables on percentage removal (β1) According to the F values reported in Table 3, it was concluded that the pyrolysis temperature (𝐴 1 ) had the strongest influence on percentage removal (β1), and the duration (𝐵 1 ) and ratio (𝐶 1 ) had approximately lower effects on this response.…”

“…The obtained standard deviations (SD%) and coefficient of variation (CV) were minimal, implying that the suggested models are dependable (Tables 3, 4, and 5) (Sellamuthu et al 2023). The signal/noise ratio (s/n) achieved in this case exceeded 4, indicating sufficient precision for the proposed models (Sellamuthu et al 2023) The impact of processing variables on percentage removal (β1) According to the F values reported in Table 3, it was concluded that the pyrolysis temperature (𝐴 1 ) had the strongest influence on percentage removal (β1), and the duration (𝐵 1 ) and ratio (𝐶 1 ) had approximately lower effects on this response. When the ratio was adjusted at center/zero, the trend for sorption capacity was quantified and the combined impact of temperature (𝐴 1 ) and time (𝐵 1 ) was illustrated by 3D RSM mesh plot of Fig.…”

“…Similarly, insufficient activation time and/or a reduced temperature of activation cannot improve the porosities of the carbonaceous adsorbent. Thus, process optimization is needed to maintain the quality of the carbon (Sellamuthu et al 2023). The higher the temperature, the more likely it is that micropores walls will deform and eventually break, to form mesopores.…”

“…5c. The reducing property of carbon can initiate to form K, K2O, CO, and CO2 gas from K2CO3 as represented by following equations (Sellamuthu et al 2023):…”

“…The adequate precision values obtained for removal percentages for β1, percentage yield β2, and fixed carbon content β3, .74, and 18.70, respectively. Therefore, the experimental data collected in this research held statistical importance for directing the design(Sellamuthu et al 2023). ANOVA and Statistical Analysis for Effect of Input Parameters/Variables on Percentage Yield (β2)…”