Papers by Keyword: Adsorption

Abstract: This study investigates the removal of radioactive cesium-137 (Cs-137) from wastewater using activated carbon derived from cassava rhizome (CRAC), composited with copper hexacyanoferrate (CuHCF) through three synthesis methods including hydrothermal (HTM), ultrasonic-assisted (US), and mechanical stirring (STIR). The objective was to enhance the availability of active adsorption sites for improved Cs-137 capture. Fourier-transform infrared (FTIR) spectroscopy revealed the formation of carboxylate ion groups (-COO^-) in the CRAC/CuHCF composites synthesized via the hydrothermal method, indicating deprotonation of carboxylic groups (-COOH) during synthesis. This transformation is believed to facilitate Cs⁺ ion binding. X-ray diffraction (XRD) analysis confirmed the presence of a face-centered cubic structure in the composite, which provides structural vacancies conducive to Cs⁺ diffusion. These findings suggest a dual adsorption mechanism involving surface complexation and lattice incorporation. BET analysis revealed that CRAC composites exhibited significantly enhanced surface area and porosity, with the HTM method providing uniform carbon dispersion and the smallest pore diameter (5.46 nm), whereas US cavitation yielded the highest pore volume (0.17 cm³/g). Batch adsorption experiments demonstrated that CRAC/CuHCF (HTM) composites achieved the highest Cs-137 removal efficiency (98.90%) and adsorption capacity (6.15 × 10⁻⁷ mg/g), outperforming composites synthesized via US and STIR methods, as well as pure CuHCF and CRAC alone. Kinetic modeling indicated that the adsorption process followed a pseudo-second-order model, suggesting chemisorption as the dominant mechanism. Furthermore, the adsorption isotherm was best described by the Freundlich model, implying multilayer adsorption on heterogeneous surfaces.

Abstract: In this study, glycidyl methacrylate was grafted onto nonwoven polypropylene fabric (PP-g-GMA) via gamma radiation-induced graft polymerization at doses of 10, 20, 30, 40, and 50 kGy. The results revealed that increasing the radiation dose led to a higher degree of grafting. A notable rise in grafting was observed at 20 kGy, reaching 45.21%, and continued to increase significantly with higher doses, 112.48% at 30 kGy, 234.43% at 40 kGy, and peaking at 340.11% at 50 kGy. To evaluate its application in radioactive wastewater treatment, the PP-g-GMA was further functionalized with Prussian blue (PB) to produce the PP-g-GMA-PB adsorbent for the removal of radioactive cesium-137 (¹³⁷Cs). Among the tested radiation doses, the adsorbent synthesized at 30 kGy exhibited the highest ¹³⁷Cs removal efficiency, achieving 72.40% adsorption within 24 h. In comparison, adsorbents prepared at 10, 20, 40, and 50 kGy showed removal efficiencies of 45.45%, 47.73%, 50.32%, and 48.70%, respectively. These findings demonstrate that the PP-g-GMA-PB adsorbent, particularly at a grafting dose of 30 kGy, holds promise for effective ¹³⁷Cs removal from radioactive wastewater, highlighting its potential for practical environmental remediation applications.

Abstract: Magnetized coal fly ash (MCFA) was utilized as a low-cost and eco-friendly adsorbent for the removal of crystal violet (CV) dye from aqueous solution. This study aims to investigate the adsorption behavior of CV onto MCFA through kinetic and isotherm evaluations. The magnetic modification was performed using Fe₃O₄ to enhance the separation efficiency and adsorption performance of raw fly ash. Batch adsorption experiments were conducted to examine the effects of contact time, initial dye concentration, pH, and adsorbent dosage. The kinetic analysis revealed that the adsorption process followed the pseudo-second-order model, suggesting chemisorption as the dominant mechanism. Isotherm modeling showed that the Langmuir model provided the best fit, indicating monolayer adsorption on a homogeneous surface, with a maximum adsorption capacity (q_m) reflecting the strong affinity of CV toward MCFA. The incorporation of magnetic properties significantly improved the adsorbent’s recovery and reusability. Overall, MCFA demonstrated excellent potential as a cost-effective magnetic adsorbent for the remediation of dye-contaminated wastewater.

Abstract: Rice husk ash (RHA), a waste product of the rice mill, is rich in silica. This study aimed to investigate the use of RHA as a potential adsorbent for the removal of free fatty acid (FFA) from the waste frying oil (WFO). Acid pre-treatment of RH prior to combustion using hydrochloric acid (HCl) was proposed to improve its adsorption performance. The synthesized acid-pretreated RHAs were characterized using Fourier Transformed Infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). It was found that the aRHAs achieved higher silica purity with low levels of organic impurities as compared to untreated RHA. Additionally, aRHAs possessed porous morphology, especially when treated with higher HCl concentration, as revealed by SEM analysis. EDS analysis confirmed the high silica purity with negligible amount of metal impurities for all the RHAs. For adsorption kinetic models and adsorption isotherms, results showed that the intraparticle diffusion model and the Langmuir isotherm gave the best description to the experimental data with the lowest Chi-square values, reported at 0.02 and 5.46, respectively.

Abstract: Synthetic dyes such as methyl orange (MO) are persistent water pollutants that pose serious environmental and health hazards due to their toxicity and resistance to biodegradation. Developing efficient, sustainable, and reusable adsorbents for dye removal remains a major challenge in wastewater treatment. This study presents the design and optimization of chitosan/polyethyleneimine/graphene oxide (CS/PEI/GO) hydrogel nanocomposite beads synthesized through controlled cross-linking with glutaraldehyde (GLA) for enhanced adsorption of MO from aqueous solutions. A Box–Behnken experimental design coupled with response surface methodology (RSM) was employed to evaluate the effects of PEI, GO, and GLA concentrations on adsorption capacity. Statistical analysis confirmed the high significance of the cubic model (F = 38.34, p = 0.0001) with a non-significant lack of fit, validating its strong predictive reliability. PEI concentration had the most pronounced effect, providing protonated amine sites for electrostatic interaction with the anionic dye, while GO increased surface area and provided oxygen-containing groups that enhanced hydrogen bonding and π–π interactions. GLA served as a cross-linker to stabilize the hydrogel structure without deactivating active sites. The optimized composition (2.0% PEI, 900 ppm GO, and 2.5% GLA) achieved a predicted adsorption capacity of 23.16 ± 1.05 mg/g, which closely matched the experimentally obtained value of 23.31 ± 1.19 mg/g, with only 2.2% deviation. These findings confirm that the CS/PEI/GO hydrogel nanocomposite provides a balanced integration of structural stability, functional site availability, and high adsorption efficiency, demonstrating its potential as a scalable, eco-friendly material for advanced dye removal and sustainable wastewater treatment.

Abstract: This study utilizes phenanthrene as the model molecule to investigate the optimization and reusability of coal-derived carbon nanoparticles for the adsorption of polycyclic aromatic hydrocarbons (PAHs). After controlled carbonization and activation, the carbon nanoparticles were synthesized using a chemical solid synthesis method and meticulously studied to determine their surface morphology and crystallinity. One factor at a time (OFAT) was used as an optimization method for the batch adsorption studies, the parameters varied including pH, contact time, adsorbent dosage, Temperature, and initial phenanthrene concentration. The optimal circumstances for phenanthrene resulted in a high removal efficiency of up to 95.3% for phenanthrene, and 96% removal for naphthalene, hence demonstrating the material's potential for PAH remediation. Subsequent batch testing confirmed the material's efficacy in removing naphthalene and phenanthrene. Furthermore, reusability studies conducted over five adsorption-desorption cycles demonstrated minimal decline in removal efficiency for Naphthalene by 10%, with a difference between the 1^st and 5^th run. hence showing robust regeneration capability and operational stability. But it shows a high decline in removal efficiency for phenanthrene. The results demonstrate the efficacy and sustainability of coal-derived carbon nanoparticles as a cost-effective adsorbent for applications addressing PAH contamination in water.

Abstract: Adsorbent beads composed of Chitosan (CS), MIL-101 (Fe), and Polyethyleneimine (PEI) were synthesized for Methyl Orange (MO) adsorption. Parametric studies testing the effects of pH and number of adsorption and desorption cycles on percent MO removal showed the beads’ good performance across a wide range of conditions. A percent MO removal of at least 93% was maintained from pH 2 to pH 9 with a maximum percent removal of 98.6% obtained at pH 3. In addition, the beads remained functional for at least 5 cycles of adsorption and desorption with a percent MO removal of 98% across the cycles. Kinetic modeling was performed and a pseudo-second order kinetic model with an R² of 0.981 was obtained implying chemisorption as the rate limiting step. Adsorption equilibrium data for MO were best fitted into the Sips isotherm model which suggests that adsorption occurs on a heterogeneous surface. From the Sips isotherm model, the maximum adsorption capacity was determined to be 1253.44 mg/g, highlighting the viability of CS – MIL-101 (Fe) – PEI beads as an adsorbent for wastewater treatment.

Abstract: Carbon dioxide (CO₂) capture is a significant chemical process that has attracted considerable interest in both academic and industrial sectors. It is essential for mitigating climate change and its related impacts on the environment and human health. Various technologies are implemented for CO₂ capture, with physical adsorption using porous material standing out as one of the most widely employed methods. Gallate-based metal-organic frameworks (MOFs) are reported to offer remarkable CO₂ adsorption capacity values, with Mg-gallate exhibiting the highest capacity, followed by Co-gallate and Ni-gallate. The mechanism of CO₂ adsorption on gallate-based MOFs, however, lacks extensive discussion. A thorough understanding of the adsorption mechanism helps in designing and synthesizing MOFs with enhanced CO₂ capture performance. Therefore, this work aims to discuss the mechanism of CO₂ adsorption on gallate-based MOFs based on the experimental pure isotherms. The experimental isotherms exhibited S-shaped curves that are related to the occurrence of gate-opening effect. These S-shaped isotherms corresponded to multistep adsorption, classifying gallate-based MOFs as flexible MOFs. The flexibility of these frameworks can be controlled by the pressure and temperature, which is important for designing specific gas storage and separation systems. In addition, the intra-particle diffusion model supported that the CO₂ adsorption occurred at the surface and mesopore of gallate-based MOFs. Given these characteristics, gallate-based MOFs can be considered as the promising physisorbent for CO₂ capture.

Abstract: This work examines the impact of critical operational parameters pH, temperature, initial copper concentration, adsorption duration, and adsorbent dosage on the efficacy of five bio-based adsorbents: pineapple pulp, tissue pulp, chitosan, chitosan-coated pulp, and chitosan-coated pineapple peel. for the removal of cupric ions from aqueous solutions. The results indicated that both pH and temperature significantly enhanced copper removal efficiency (Re) and adsorption capacity (qe) for all materials tested. Conversely, higher initial copper concentrations led to a decrease in Re but an increase in qe, indicating greater metal loading per unit mass of adsorbent. Adsorption time had minimal influence on performance, while increased adsorbent dosage significantly improved Re only for chitosan-coated pulp and caused a general decline in qe due to reduced surface utilization. Pearson correlation analysis supported these findings, revealing significant positive correlations of pH and temperature with both performance indicators and a dual effect of feed concentration. Dosage and contact time showed weak, statistically non-significant correlations. This analysis identifies pH, temperature, and initial metal content as the principal parameters affecting biosorption efficacy and provides essential recommendations for optimizing conditions in the treatment of copper-contaminated wastewater.

Abstract: This work presents the preparation of a bioadsorbent from the shells of Hyphaene Thebaica. The shells were first characterized. Analyses such as bulk density, pH at zero charge point, specific surface area (BET), thermogravimetric analysis (ATG/ATD), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (IR) were determined. The results obtained showed that the zero charge point pH equals 6, the specific surface area value obtained by the BET method is 235 m²/g and the pore diameter is 2.132 nm. Next, tests were carried out to determine the adsorption capacities of diiodine and methylene blue. The results obtained showed a methylene blue index of 11.56 mg.g^-1 and an iodine index equal to 456.84 mg.g^-1. The adsorption mechanisms studied revealed that pseudo-second-order kinetics was the model that best fitted the experimental data. Finally, the effects of adsorbent mass, stirring speed and concentration were investigated using a Box-Behnken design. Optimal factors were obtained for a concentration of 100 mg/L, a mass of 0.200 g, an adsorption capacity of 5.073 mg/g, agitation of 400 rpm and a removal rate of 97.605 % with a desirability of 0.923.