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The utilization of unsaturated fatty acids as a renewable source for the production of epoxides makes it an appealing alternative. However, there has been limited research on optimizing the process parameters for epoxidized sunflower oil, resulting in its underutilization. Therefore, this study aimed to optimize the catalytic epoxidation of sunflower oil concerning the oxirane content. The epoxidation of sunflower oil was conducted using an in situ peracetic acid method, where hydrogen peroxide served as the oxygen donor and carboxylic acid acted as the oxygen carrier. The findings revealed that the optimal reaction conditions for producing epoxidized sunflower oil-derivative linoleic acid with the highest oxirane content were a catalyst loading of 0.2% zeolite, a molar ratio of hydrogen peroxide to linoleic acid of 1:1, string speed of 300 rpm, and formic acid as oxygen carrier. By employing these optimal conditions, the maximum relative conversion of sunflower oil derived linoleic acid to oxirane was achieved at 63.9%. Lastly, employing genetic algorithm, the results exhibit excellent agreement with the experimental data, thereby confirming the accuracy and validity of the kinetic model.

Previous research has shown GC's reliable performance as an adsorbent in water and wastewater treatment, but broader applications remain underexplored. This study focuses on treating GC with KOH to eliminate methylene blue (MB) dye. The FTIR results indicated an enrichment of carbonyl groups on the GC surface, which enhanced the rate of MB adsorption. SEM analysis of both treated and untreated GC revealed that the treated char exhibited prominently developed pores and displayed a distinct open-porous structure, reminiscent of a honeycomb-like porous formation. The result from Brunauer–Emmett–Teller (BET) analysis reveals that BET surface area (469.27 m2/g) and total pore volume (0.2728 cm3/g) of treated GC improved after activation. Increasing the initial concentration of MB from 100 to 250 mg/L resulted in a decrease in its removal from 82.1 to 50.87%, respectively. Meanwhile, raising the pH from 3 to 9 enhanced MB adsorption from 85.46 to 97.06%. As the temperature increased from 30 to 60 °C, the adsorption process accelerated, leading to an increase in the percentage of dye removal from 89.11 to 96.63%. Matlab curve fitting tools were used to fit non-linear isotherm and kinetic models. The n-BET isotherm and Pseudo-First-Order (PFO) kinetic models demonstrated an excellent fit to the experimental data, evidenced by the highest R2values, specifically 0.99206 and 0.9577–0.9855, respectively. These findings strongly suggest a multilayer adsorption process taking place on the uniform surface of treated GC. Thermodynamic analysis affirms the endothermic and spontaneous nature of the adsorption process, corroborated by negative ΔG° and positive ΔH° values ranging from -11.0722 to -8.1916 kJ/mol and from 0.694 to 0.857 kJ/mol, respectively.

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In this work, melunak and rubberwood-based activated carbon (MAC and RAC) were prepared via microwave induced KOH activation for Remazol Brilliant Violet 5R (RBV5R) dye removal from aqueous solution. Batch adsorption experiments were carried out to evaluate the influence of pH, initial dye concentration, and contact time. The textural characterization shows high BET surface area of 914.0 and 796.0 m2/g for MAC and RAC, respectively, which indicate that they are comprised of a micro-mesoporous structure. Langmuir isotherms provided the best model for MAC and RAC adsorption data. The adsorption capacities of RBV5R onto MAC and RAC estimated by the Langmuir model were 238.33 and 204.08 mg/g, respectively. The pseudo-first-order, pseudo-second-order, and Elovich model equations were used to analyse the kinetic data of the adsorption process, and both data fitted well with the pseudo-second-order kinetic model. Film diffusion was the rate-limiting step controlling adsorption based on intraparticle diffusion and the Boyd plot. The adsorption mechanisms involved are pore filling, hydrogen bonding, n–π interactions, and π–π interactions. The thermodynamic parameters confirmed that the adsorption was spontaneous, feasible, and endothermic. Furthermore, a mechanism including physisorption and chemisorption of RBV5R on MAC and RAC has been proposed. The desorption study predicts excellent regenerative efficacy of both MAC and RAC for up to four cycles.

In this study, the preparation conditions for the gasification waste-based activated carbon (GWAC) were optimized with malachite green (MG) dye removal and GWAC yield as responses. The adsorption equilibrium, kinetic behavior, and thermodynamics properties were also analyzed. The optimum conditions for synthesizing GWAC were found at a radiation power, time, and impregnation ratios of 616 W, 1 min, and 1.06 g g–1, respectively, which resulted in an 89.98% yield of GWAC and 99.01% MG removal. This sample shows the surface area and total pore volume of 351.92 m2g–1and 0.22 cm3, respectively. For the isotherm study, the Fritz–Schlünder model fitted the adsorption data very well with an R2value of 0.9919–0.9932. The results of the kinetic study showed that the MG adsorption followed a pseudo-first-order kinetic model (R2= 0.9625–0.9871). The film diffusion was found to be the rate-limiting step of MG adsorption. The adsorption of the MG dye onto GWAC was an endothermic and spontaneous process with ΔH of 9.183 kJ mol–1. In continuous mode, Thomas and Yoon–Nelson models successfully predicted the MG adsorption on the GWAC. GWAC demonstrates its commercial feasibility based on a low production cost of 0.23 USD kg–1.

In the era of the fifth generation (5G) and the Internet of Things (IoT), electromagnetic interference (EMI) poses a significant challenge. The rapid growth of wireless communication applications leads to increased electromagnetic (EM) pollution, which can have adverse health effects. To address this issue, electromagnetic absorbers (EMAs) play a critical role in eliminating EMI and reducing EM pollution between electronic devices. The focus is now on developing diverse microwave absorbing materials (MAMs) with different structures to cover a wide range of frequencies while remaining cost‐effective and effective at high angles of incidence radiation. This article comprehensively reviews EMAs, highlighting their design parameters and importance in achieving high‐efficiency absorption. The review covers absorber theory, structure, materials for various frequency ranges, and the mechanisms responsible for dissipating electromagnetic waves (EMWs). Analytical and numerical methods for modeling and analyzing EMAs are discussed, along with performance indicators and testing methods. The role of absorbers in different applications is explored, and emerging research directions for enhancing microwave absorbers are also highlighted. This review paper comprehensively examines electromagnetic absorber technologies. It aims to foster a deeper understanding and advancement in developing efficient electromagnetic absorbers by covering theoretical aspects, modeling techniques, measurement methodologies, and testing procedures. The paper is a valuable resource for researchers and practitioners in EMAs.

In this study, rice husk activated carbon (RHAC) was synthesized by physicochemical activation, which consists of heat treatment with CO2gasification and KOH chemical treatment to eliminate arsenic (As) from the polluted water. Initial arsenic concentrations, solution pH, solution temperature and contact time are the parameters that have been tested in this study. The characterization study showed that RHAC has a high BET surface area (815.52 m2/g) and its pore structure was found to be mesoporous with an average pore diameter of 2.96 nm. Characterization studies, including X-ray diffraction analysis (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were employed to determine the RHAC’s performance. The adsorption of As towards RHAC followed the Freundlich isotherm model and pseudo-first order with adsorption process was favorable at higher arsenic concentrations. The mechanism study also signified that the adsorption of As-RHAC was limited by film-diffusion. Thermodynamic studies indicated that the As-RHAC adsorption system was endothermic, random, spontaneous, feasible in nature and governed by the chemisorption process. Desorption and regeneration studies of RHAC showed that it can be utilized up to 5 cycles and is stable for the water treatment facilities.

The successful preparation of pineapple peel activated carbon (PineAC) using a low–cost and environmentally friendly method presented a promising alternative for the utilization of pineapple peel (PineP) waste. The remarkable regeneration capability of PineAC significantly enhances its possible reusable adsorbent for the effective Remazol Brilliant Violet 5 R (RBV 5 R) dye adsorption. The Polymath software was employed to gain deeper insights into the mass transfer process and optimize the adsorption kinetics. PineAC's performance was investigated using characterization techniques such as surface analyzer, Energy Dispersive X–ray (EDX), Fourier Transform Infrared (FTIR) spectroscopy, and X–Ray Diffraction (XRD) analysis. The optimal conditions for the adsorption of PineAC–RBV 5 R dye were at 60°C, in an acidic medium, and at 300 mg/L. The Langmuir isotherm model successfully described the monolayer behaviour of RBV 5 R dye adsorption onto PineAC at 30 and 45°C. In contrast, the Freundlich isotherm model was applicable at 60°C. The PineAC–RBV 5 R dye exhibited a maximum adsorption capacity (qmax) of 66.300 mg/g. The kinetic data demonstrated excellent agreement with the Polymath Mass Transfer (PMT) model, successfully capturing adsorption behavior. The rate constant, kPTM, displayed an increasing trend as the RBV 5 R initial concentration rose from 25 mg/L to 300 mg/L. Furthermore, the PMT model accurately predicted the adsorption surface area, aPMT, to be 466.6560 m2/g, closely matching the actual mesopores surface area of 547.8500 m2/g. This remarkable accuracy highlights the reliability and robustness of the PMT model in describing the adsorption process. PineAC–RBV 5 R dye adsorption exhibited consistent thermodynamic behaviour characterized by endothermic adsorption (ΔH°=28.49 kJ/mol), a physisorption mechanism (Ea=24.02 kJ/mol), and spontaneity (ΔG°=10.74 kJ/mol). The potential mechanisms involved in the PineAC–RBV 5 R dye adsorption included n–π interactions, hydrogen bonding, and π–π interactions. The regeneration effectiveness of PineAC–RBV 5 R dye adsorption was 72.30% for the third cycle without causing any surface morphological alterations in agreement with SEM images and EDX spectra. Investigating the adsorption mechanisms and the potential for further functionalization of PineAC could provide opportunities for enhanced performance and expanded applications in sustainable wastewater treatment.

AbstractRambutan seeds (Nephelium lappaceumL.)-based activated carbon (RSAC) was prepared using potassium hydroxide (KOH) activation and carbon dioxide (CO2) gasification methods. The adsorbent prepared was characterized using Fourier transform infrared, SEM, proximate analysis, and BET techniques, respectively. The effects of three variable parameters; activation temperature, activation time, and chemical impregnation ratio (IR) (KOH: char by weight) on the preparation of RSAC used for the removal of MG dye was investigated. Based on the central composite design, quadratic and two factor interaction (2FI) models were, respectively, employed to correlate the effect of variable parameters on the preparation of RSAC used for the percentage MG dye removal and activated carbon yield. From the analysis of variance, the most influential factor on each experimental design response was identified. The optimum conditions of MG dye removal by RSAC are: activation temperature (802°C), activation time (1.0 h), and IR (2.4), respectively. The percentage MG dye removal obtained was 91.45% resulting in 22.56% RSAC yield. The percentage error between predicted and experimental results for the removal of MG dye is 2.4%. The effects of operational parameters like pH, initial dye concentration, contact time, and solution temperature were investigated using batch method. Graphical correlations of eight different adsorption isotherm models were carried out. Freundlich isotherm fitted the adsorption data most. The data were also analyzed by the Lagergren pseudo-first-order, Ho Mc Kay pseudo-second-order, Elovich and Avrami kinetic models. Pseudo-second-order kinetic model best represents the kinetic data and the mechanism of adsorption was controlled by both film and intraparticle diffusions. Thermodynamic studies gave negative ∆G° values, indicating that the process of MG dye adsorption onto RSAC was spontaneous. The positive values of ∆H° and ∆S° suggest that the process of dye adsorption was endothermic.

Rambutan seeds (Nephelium lappaceumL.)-based activated carbon (RSAC) was prepared using potassium hydroxide (KOH) activation and carbon dioxide (CO2) gasification methods. The adsorbent prepared was characterized using Fourier transform infrared, SEM, proximate analysis, and BET techniques, respectively. The effects of three variable parameters; activation temperature, activation time, and chemical impregnation ratio (IR) (KOH: char by weight) on the preparation of RSAC used for the removal of MG dye was investigated. Based on the central composite design, quadratic and two factor interaction (2FI) models were, respectively, employed to correlate the effect of variable parameters on the preparation of RSAC used for the percentage MG dye removal and activated carbon yield. From the analysis of variance, the most influential factor on each experimental design response was identified. The optimum conditions of MG dye removal by RSAC are: activation temperature (802°C), activation time (1.0 h), and IR (2.4), respectively. The percentage MG dye removal obtained was 91.45% resulting in 22.56% RSAC yield. The percentage error between predicted and experimental results for the removal of MG dye is 2.4%. The effects of operational parameters like pH, initial dye concentration, contact time, and solution temperature were investigated using batch method. Graphical correlations of eight different adsorption isotherm models were carried out. Freundlich isotherm fitted the adsorption data most. The data were also analyzed by the Lagergren pseudo-first-order, Ho Mc Kay pseudo-second-order, Elovich and Avrami kinetic models. Pseudo-second-order kinetic model best represents the kinetic data and the mechanism of adsorption was controlled by both film and intraparticle diffusions. Thermodynamic studies gave negative ∆G° values, indicating that the process of MG dye adsorption onto RSAC was spontaneous. The positive values of ∆H° and ∆S° suggest that the process of dye adsorption was endothermic.

In this present study, rubber seed-coated activated carbon (RSCAC) was used as a natural adsorbent to remove basic (MB), acid (MR) and reactive (RBV) dyes using batch process. Each dye in the adsorption process was tested at different initial concentration from 50-500 mg/l. Different dyes showed different percentage removals. The highest removal was recorded by MB which was up to 99.9 %. The experimental data was analyzed with Langmuir and Freundlich adsorption models. The data fitted well with Langmuir. The adsorption capacity were 332.99, 210.33 and 155.37 mg/g for MB, MR and RBV, respectively.

AbstractActivated carbon produced from pomelo peels (PPAC) was tested for its effectiveness in the removal of malachite green (MG) dye from aqueous solution. The PPAC prepared was characterized using TGA, BET, FTIR, SEM, pHpzc, Elemental analysis and Boehm titration, respectively. The extent of dye adsorption was investigated as a function of pH, contact time, adsorbate concentration and solution temperature. Dye removal was pH dependent, resulting in 95.06% removal at pH 8.0. Quantum chemical studies suggested that the cationic MG dye possessed minimal molecular size at planar geometry coupled with high-electrostatic interaction thereby, enhancing the adsorption at high pH. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) equilibrium isotherms were used to fit the adsorption data. Langmuir isotherm fit the adsorption data most with maximum monolayer adsorption capacity of 178.43 mg/g. The kinetic data fitted the pseudo-second-order model with correlation coefficient greater than 0.99. The mean free energy E(kJ/mol) got from the D–R isotherm indicated physisorption mechanism Thermodynamic parameters; Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) changes were also calculated, and the values indicated that the adsorption process was spontaneous and endothermic in nature. Regeneration efficiency of spent PPAC was studied using 0.2 M HCl, the efficiency was found to be in the range of 92.71–96.35% after four cycles. The study showed that PPAC can be used as an effective, low cost and environmentally friendly adsorbent for the removal of MG dye from aqueous solution.

Activated carbon produced from pomelo peels (PPAC) was tested for its effectiveness in the removal of malachite green (MG) dye from aqueous solution. The PPAC prepared was characterized using TGA, BET, FTIR, SEM, pHpzc, Elemental analysis and Boehm titration, respectively. The extent of dye adsorption was investigated as a function of pH, contact time, adsorbate concentration and solution temperature. Dye removal was pH dependent, resulting in 95.06% removal at pH 8.0. Quantum chemical studies suggested that the cationic MG dye possessed minimal molecular size at planar geometry coupled with high-electrostatic interaction thereby, enhancing the adsorption at high pH. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) equilibrium isotherms were used to fit the adsorption data. Langmuir isotherm fit the adsorption data most with maximum monolayer adsorption capacity of 178.43 mg/g. The kinetic data fitted the pseudo-second-order model with correlation coefficient greater than 0.99. The mean free energy E(kJ/mol) got from the D–R isotherm indicated physisorption mechanism Thermodynamic parameters; Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) changes were also calculated, and the values indicated that the adsorption process was spontaneous and endothermic in nature. Regeneration efficiency of spent PPAC was studied using 0.2 M HCl, the efficiency was found to be in the range of 92.71–96.35% after four cycles. The study showed that PPAC can be used as an effective, low cost and environmentally friendly adsorbent for the removal of MG dye from aqueous solution.

AbstractThe adsorption of a group of heavy metals namely, Zn2+, Ni2+, and Cd2+onto olive stones activated carbon (OSAC) was carried out in this work. The effects of different reaction parameters, such as the adsorbent dosage, contact time, shaking speed, and initial pH, on pollutant removal efficiency were investigated. Adsorption of Zn2+, Ni2+, and Cd2+was effectively explained by Langmuir and Freundlich isotherms. OSAC efficiently removed 99.03% Zn2+, 97.34% Ni2+, and 94.88% Cd2+at pH 5 and shaking speed 200 rpm. Surface characteristics of the prepared AC were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer-Emmett-Teller surface area, total pore volume and average pore diameter of the prepared AC were 886.72 m2/g, 0.507 cm/g, and 4.22 nm, respectively. The equilibrium data of the adsorption were fitted well to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Zn2+11.14 mg/g, followed by Ni2+8.42 mg/g and Cd2+7.80 mg/g. A pseudo-second-order model sufficiently described the adsorption kinetics, which indicated that the adsorption process was controlled by chemisorption. The results revealed that the OSAC has the potential to be used as a low-cost adsorbent for the treatment of wastewaters contaminated with heavy metals.

The adsorption of a group of heavy metals namely, Zn2+, Ni2+, and Cd2+onto olive stones activated carbon (OSAC) was carried out in this work. The effects of different reaction parameters, such as the adsorbent dosage, contact time, shaking speed, and initial pH, on pollutant removal efficiency were investigated. Adsorption of Zn2+, Ni2+, and Cd2+was effectively explained by Langmuir and Freundlich isotherms. OSAC efficiently removed 99.03% Zn2+, 97.34% Ni2+, and 94.88% Cd2+at pH 5 and shaking speed 200 rpm. Surface characteristics of the prepared AC were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer-Emmett-Teller surface area, total pore volume and average pore diameter of the prepared AC were 886.72 m2/g, 0.507 cm/g, and 4.22 nm, respectively. The equilibrium data of the adsorption were fitted well to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Zn2+11.14 mg/g, followed by Ni2+8.42 mg/g and Cd2+7.80 mg/g. A pseudo-second-order model sufficiently described the adsorption kinetics, which indicated that the adsorption process was controlled by chemisorption. The results revealed that the OSAC has the potential to be used as a low-cost adsorbent for the treatment of wastewaters contaminated with heavy metals.

The adsorption of heavy metals Fe2+, Pb2+, and Cu2+onto olive stone activated carbon (OSAC) was investigated in this study. The effects of different reaction parameters (i.e. adsorbent dosage, contact time, shaking speed, and initial pH) on the pollutant removal efficiency were determined. The adsorption processes of Fe2+, Pb2+, and Cu2+were effectively explained using Langmuir and Freundlich isotherms. OSAC efficiently removed 99.39% Fe2+, 99.32% Pb2+, and 99.24% Cu2+at pH 5 and with 200 rpm shaking speed. The adsorption equilibrium data were best represented by the Langmuir model, and the monolayer adsorption capacities were found to be 57.47, 22.37, and 17.83 mg/g for Fe2+, Pb2+, and Cu2+, respectively. A pseudo-second-order model sufficiently described the adsorption kinetics, which indicated that the adsorption process was controlled by chemisorption. The results revealed that OSAC can be used as a low-cost adsorbent for the treatment of wastewaters contaminated by heavy metals.

•A novel process for the preparation of olive stone activated carbon (OSAC) is developed.•Effects of radiation power, radiation time and impregnation ratio on cadmium removal were investigated.•Equations of cadmium removal and OSAC yield with respect to OSAC preparation have been developed.•Short preparation time 7min is required comparing with that used in literature.•The microwaved OSAC efficiently removed 95.32% of cadmium with high yield 85.15%.

A series of activated carbon from cocoa shell (CSAC) was prepared from cocoa shell pellet (CS) by carbonization and followed by physical activation using CO2as the activation agent. Carbonization was done in a flow of N2using a fixed-bed reactor at 400, 500, 600, 700, 800 and 900°C with soaking time at the carbonization temperature for an hour. The selected char indicated completion of the aromatization process which suggests no structural changes beyond this temperature. Char monolith, carbonized at 800°C were activated at 850°C using a fixed bed reactor for different burn-offs. The drilling of the pores possibly occurred at burn-off below 60% which indicated by huge increase of absolute pore volume against the burn-off. The surface area at 48.5% burn-off was estimated at 366.26m2g-1. High burn-off product tends to develop larger micropore and moderate BET surface area. The largest surface area of CSAC was recorded at 558.25m2g-1. During activation, the aromatization of CSAC increased but the aliphacity decreased accordingly.

The performance of a thermoelectric power generator for powering wireless sensor node has been studied and evaluated. This study covers the results obtained from two configurations of thermoelectric cell with heat source temperatures range from 40 to 230 oC. It was found that the highest output voltage is 9.08 V belong to configuration B with two parallel thermoelectric cells. This configuration was capable to power up sensor node compared to configuration A with the lowest heat source temperature at about 200 oC. To enhance the capability of the configurations, DC boost converter circuit has been developed and tested. By connecting to the DC boost converter, configuration A can power up the wireless sensor node with heat source temperature at about 220 oC while the minimum heat source temperature for configuration B was reduced from 200 to 170 oC. This study identified the optimum operation condition to power up wireless sensor node by thermoelectric power generator for remote application and make conclusion as to how to increase the performance of thermoelectric power generator by introducing DC boost converter.

Usually, a few preliminary stages have been done for raw materials before the actual production of activated carbon such as materials crushing, milling and sieving to an appropriate particle size. Particle size is important for the subsequent handling of the raw material, such as mixing with a catalyst or impregnation, but it can also affect the properties of the subsequent activated carbon. This research was assessed the effect of different olive stone particle size on activated carbon production by KOH using the yield and surface area response. Three particle size ranges were examined, namely 1-2mm, 2-4.75 and the raw material in its original form. The results demonstrated that the most suitable form was 2mm to 4.75mm which resulted in 38.67% of yield and 886.72 m2 g-1 of a surface area and it has more rigidity compared with finer particle size and has more surface area and yield compared with olive stone in its original form.

The conditions for the preparation of rubber (hevea brasiliensis) seed coat based activated carbon (RSCAC) treated with NaOH were optimized through response surface methodology (RSM). The effects of three preparation variables: the activation temperature, activation time and NaOH impregnation ratio (IR) on Remazol Brilliant Blue R (RBBR) removal from aqueous solutions and RSCAC yield were investigated. Based on the RSM, two quadratic models were respectively developed to correlate the preparation variables to the RBBR percentage removal and carbon yield. The significant factors on each experimental design response were identified from the analysis of variance (ANOVA). The optimum conditions for RSCAC preparation were obtained by using activation temperature of 700 oC, activation time of 1.0 h and IR of 1.0, which resulted in 70.82% of RBBR removal and 24.93% of RSCAC yield.

Pomegranate fruit peel activated carbon (PFPAC) was prepared using potassium hydroxide impregnation and carbon (IV) oxide gasification methods for the remediation of Methylene blue (MB) from aqueous solution. The design of experiment for the optimization of variables for preparing activated carbon sourced from pomegranate fruit peel was carried out using response surface methodology (RSM). The adsorbent was characterized using BET, SEM, FTIR, and elemental analysis respectively. The BET analysis showed an improved surface area from raw PFP (1.01 m2/g) to PFPAC (845.96 m2/g). The optimum conditions for the adsorption of MB dye are 375 W, 0.9, and 4.5 min for radiation power, impregnation ratio, and activation time respectively. These resulted in high percentage of MB dye removal and PFPAC yield of 83.4% and 30.8% respectively. For batch equilibrium studies, the adsorption of MB dye onto the optimized PFPAC showed a strong dependence on the temperature, contact time, and initial MB dye concentration. Kinetic studies revealed rapid MB dye uptake at the initial stages of 0 – 3 h and attained equilibrium at 6 h for initial concentrations of 25 – 300 mg/L. Langmuir maximum monolayer adsorption capacities,qo(max), at temperatures of 303, 318, and 333 K are 250.00, 239.05, and 235.58 mg/g respectively, thus suggesting a favourable adsorption at low temperature. Modeling of the adsorption data using three kinetic models, revealed that pseudo first order (PFO) model best explained the adsorption process of MB dye onto PFPAC indicating a physisorption process. Chemically activated PFPAC was found to be valuable and effective for sequestrating MB dye from the aqueous solutions.

Lemongrass leaf activated carbon (LLAC) was prepared using physicochemical process for MB dye removal from aqueous systems. The adsorbent was characterized by SEM and FTIR techniques respectively. Batch adsorption studies were investigated using four operational parameters: initial dye concentration (25 mg/L-500 mg/L), contact time (0 hr to 24 hr), temperatures (30 °C - 60 °C) and pH (2–12). The surface chemistry analysis shows that upon the interaction of MB dye with the adsorbent, the bands are significantly altered after MB dye adsorption e.g., band at 2125 cm−1, 1650.09–1514 cm−1, 1386.98–1 273.05 cm−1, 1088.60 cm−1, etc. disappeared upon the interaction of the LLAC with the MB dye. Whereas, the surface morphology shows that the activation process with NaOH has contributed to the widening and formation of pores on the LLAC surface which is required for efficient MB dye uptake. MB dye adsorption is strongly dependent on initial dye concentrations while the percentage MB dye removal by LLAC increases with increasing solution pH until it reached the optimum at pH 12 with maximum percentage removal of 64.36%. The equilibrium data were fitted into eight different isotherms. Koble-Corrigan model best fitted the adsorption data with a maximum sorption capacity of 342.9 mg/g and R2 = 0.999. The pseudo-first-order kinetic model best explained MB dye adsorption onto LLAC. Thermodynamic parameters (such as ∆G0, ∆H0, and ∆S0) were also determined. The sorption process for MB dye removal was endothermic while the reaction mechanism follows the physisorption process.

This study explored the use of pomegranate-fruit-peel activated carbon (PFPAC) prepared using potassium hydroxide (KOH) activation and carbon dioxide (CO2) gasification methods for the adsorptive removal of Remazol Brilliant Blue R (RBBR) dye from synthetic wastewater. The adsorbent was characterized using BET, FTIR, SEM and proximate analysis respectively. Central composite design (CCD) in response surface methodology (RSM) was used for the optimization of RRBR dye adsorption onto PFPAC surface. Quadratic model and two-factor interaction models were developed for the percentage RBBR dye removal and PFPAC yield. Model suitability was judged using Analysis of Variance (ANOVA). BET surface area showed a significant improvement from 1.01 m2/g (raw PFP) to 845.96 m2/g (PFPAC), aside volatile matters (60.63% to 17.6%) which gave a sharp reduction, other proximate analyses parameters increased from PFP to PFPAC: fixed carbon contents (15.34% to 75.24%), carbon content in the precursor was found to increase from 30.44% (raw PFP) to 78.32% (PFPAC). The FTIR analysis showed the presence of stretching bands such as OH, CH, OCO, CC, CO, NO, CO and CCH:CH which are altered after activation and adsorption process, leading to additional CO stretching belonging to lactone, ketone, and carboxylic anhydride and CH bending vibrations after RBBR dye adsorption. The optimum removal conditions for RBBR dye adsorption were 350-watt, 4.50 min and 0.90 for radiation power, radiation time and IR respectively. This led to a maximum RBBR dye removal percentage of 81.35% and PFPAC's yield percentage of 31.2%. The error percentage between predicted and actual results for the preparation of PFPAC was 1.92%, indicating that the results of experimental studies were in perfect agreement with those suggested from model. Thus, the prediction by the model was in good conformity with actual outcome. PFPAC was found to be effective in trapping RBBR dye from aqueous solution.

Lemongrass leaf based activated carbon (LGLAC) was prepared using physico-chemical methods for methyl red (MR) dye removal from aqueous solutions. The surface chemistry of LGLAC before adsorption revealed the presence of different functional groups: O-H, C-H, C=O, CH3, C=C, N-O, C-O and C-N which were shifted after methyl red dye adsorption. Brunauer-Emmett-Teller surface and mesopore areas are 836.04 m2/g and 598.6 04 m2/g, whereas, the average pore diameter and total pore volume of LGLAC are 3.62 nm and 0.472 cm3/g respectively. Batch adsorption was studied using different parameters: initial dye concentrations (25–500 mg/L), contact time (0–24 h), solution temperature (30–60 °C) and solution pH (2–12). Adsorption of methyl red dye was observed to increase with increase in initial dye concentration, contact time and solution temperature. The methyl red dye adsorption uptake and percentage removal at equilibrium showed that the adsorption process is majorly dependent on the initial dye concentration. Optimum percentage of methyl red dye removed was observed at pH 2. The adsorption process of methyl red dye onto LGLAC was endothermic in nature. Thermodynamic parameters, including entropy change (ΔS0), enthalpy change (ΔH0), and Gibbs free energy change (ΔG0) were evaluated. The adsorption process was endothermic and the mechanism followed a physisorption process.