Papers by Keyword: Adsorption

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.

Abstract: Cyclodextrin Covalent-Organic Frameworks (CD-COFs) represent a distinctive class of porous crystalline materials that combines the structural order and tunable porosity of covalent-organic frameworks with the host–guest recognition and chiral selectivity of cyclodextrins. This review presents an analysis of recent progress in CD-COF research with emphasis on applications already demonstrated in the literature. CD-COFs show strong performance as highly selective stationary phases for chromatographic separations, enabling resolution of positional isomers and chiral enantiomers through inclusion complexation within ordered cavities supported by a high-surface-area framework. Framework architecture also enables rapid and selective adsorption of micropollutants, perfluorinated compounds, and other persistent contaminants, pointing to use in sustainable water treatment. Studies further report roles in energy and environmental technologies that include solid-state lithium-ion conduction, carbon capture, functional membranes for antibacterial activity, and enantioselective separation. Knowledge gaps persist in scalable and environmentally friendly synthesis, broader coverage of underexplored application spaces, and the translation of host–guest design rules into predictive structure–property relationships. Continued progress positions CD-COFs as a versatile platform for next-generation functional materials that address challenges in separation science, energy storage, and environmental remediation.

Abstract: This study explored the feasibility of removing nickel (Ni) and Pb (II) from water solutions using the adsorption technique by cellulose recovered from office paper waste. Metal removal is required to reduce the direct or indirect exposure of industrial waste to the environment, due to its potential for harm to human health and ecosystems. The release criterion is maintained to keep the efficient wastewater treatment of the metals of concern, which are toxic to both humans and other organisms. The cellulose was first prepared from office paper waste. The removal values can be rationalized as follows: Lead removal efficiencies of were obtained upto %95.0632, while the removals of nickel were obtained as 54.3866%. The adsorption process was effective with the initial metal concentration and the adsorbent dose used. In addition, the study focused on the competition between the adsorption of lead and nickel ions, which inhibited their removal in a mixture. To sum up, in the present study, the prospects of removing heavy metals by low-cost renewable materials are demonstrated, and in general, those concerning the protection of the environment and the minimization of waste.

Abstract: Azolla pinnata extract and iron chloride were combined under optimized conditions using Response Surface Methodology (RSM) to synthesize Azolla pinnata-iron oxide nanoparticles (AP-IONPs). The study investigated the effects of three key parameters mixing ratio of iron chloride to Azolla pinnata extract (v/v), solution pH, and mixing temperature on the removal efficiency of nickel (Ni²⁺) ions from aqueous solutions. A Central Composite Design (CCD) was employed to develop two-factor interaction (2FI) and quadratic models describing the influence of these variables on nanoparticle synthesis and adsorption performance. Analysis of Variance (ANOVA) was used to determine the most significant factors affecting Ni removal. The optimal synthesis conditions were identified as a mixing ratio of 2.5:1, solution pH of 2.5, and a temperature of 70 °C. Under these conditions, the predicted and experimental Ni removal efficiencies were 98.1% and 97.1%, respectively, with a prediction error of just 1.02%. Keywords: Green synthesis; Response surface methodology; Azolla pinnata; Nanoparticles Heavy metals; Nickel; Adsorption.

Abstract: Water pollution causes about 1.4 million deaths annually, and in Nigeria, especially in rural areas and the Niger Delta, millions lack access to clean water due to crude oil contamination. This study investigates using carbonized Flamboyant (Delonix regia) pods as a sustainable, low-cost adsorbent for removing petroleum hydrocarbons from contaminated water, promoting agricultural waste valorization and pollution reduction. Water samples collected from Obiakpor in Port Harcourt, Nigeria, were found to contain 75.22 mg/L of total petroleum hydrocarbons (TPH) and were subsequently used to evaluate the efficiency of the prepared adsorbent. Activated carbon was prepared by washing, drying, carbonizing the pods at 550 °C, chemically activating with KOH, neutralizing, then drying and sieving for uniformity. Carbonization yielded 30.2%, with proximate analysis showing low moisture (1.86%), moderate ash (4.94%), and high volatile matter (77.81%), favoring thermal stability and pore formation. Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (BET) revealed a highly porous structure with an average pore diameter of 20 μm and a large surface area of 226.4 m²/g. X-ray Diffraction (XRD) confirmed a semi-crystalline structure dominated by graphite (36 wt.%) and silicate minerals, enhancing mechanical strength and π–π interactions. Thermogravimetric Analysis (TGA showed that thermal stability was maintained between 300–500°C. Adsorption tests showed TPH removal increased with adsorbent dosage up to 0.2 g, reaching equilibrium afterward. The Freundlich isotherm best described the adsorption (R² = 0.9104), indicating multilayer adsorption on a heterogeneous surface, supported by high constants (K_f = 166.36; n = 2.35). Kinetic studies indicated rapid adsorption within 25 minutes, fitting the pseudo second order model (R² = 0.9575). These findings confirm that carbonized Flamboyant tree pods (FTP) are effective, renewable, and thermally stable adsorbents for petroleum-contaminated water treatment.

Abstract: The modification of titanium dioxide (TiO₂) with zirconium dioxide (ZrO₂) supported by chitosan (CS) was carried out to obtain a binary oxide system, which should have the properties of both components such as high stability, solar propulsion, non-toxicity and good corrosion resistance. The sample with a ratio of 1:1:3 (TiO₂:CS:ZrO₂) showed the best results with a photocatalytic degradability of 99 % after 90 minutes at a pH of 7 and in 10 ppm Malachite Green (MG). Under visible light, the photocatalytic degradability of the CS/TiO₂-ZrO₂ hybrid was more than 90 %. The enhanced photocatalytic degradation of MG by hybrid catalyst beads was attributed to the synergistic effect of hybrid CS/TiO₂-ZrO₂.