Papers by Keyword: Adsorption

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.

Abstract: The discharge of antibiotics such as cefuroxime (CFX) into the environment poses significant risks to human health and aquatic ecosystems due to the emergence of antibiotic resistance. This study evaluated the efficiency of Blighia sapida leave-derived biochar (BSLB) as an eco-friendly and cost-effective adsorbent for removing CFX from aqueous media. Effect of adsorption operating parameters such as BSLB dosage, contact time, temperature, and initial CFX concentration were investigated. Extent of CFX removal was discovered to differ with contact time, adsorbent dose, temperature and initial concentration of drug. Adsorption isotherm and kinetics parameters of the CFX molecule sequestration process were also evaluated Pseudo-second-order kinetics adequately described the adsorption process, which indicates chemisorption is the most plausible mechanism for CFX removal. The Langmuir isotherm model is found to be the best appropriate to describe the adsorption process. The monolayer saturated adsorption capacity of BSLB was found to be 33.50 mg/g. Regeneration experiments demonstrated over 80% efficiency after four cycles, confirming the reusability of the prepared biochar. Therefore, the as-prepared Blighia sapida leave-derived biochar found to be efficient and sustainable biosorbent for the CFX antibiotic removal from liquid phase media.

Abstract: The electronic structure of ultrathin Na/GaN interfaces was studied using photoelectron spectroscopy with synchrotron radiation in the photon energy range of 75–770 eV. The experiments were carried out in situ in ultrahigh vacuum of 5·10^–10 Torr with submonolayer sodium coverages on the gallium nitride surface. The photoemission spectra of the Ga 3d and N 1s core levels were studied at different excitation energies. It was found that Na adsorption causes a decrease in the intensity and a shift in the spectra of the Ga 3d and N 1s core levels towards higher binding energies. It was found that the sodium adsorption leads to some changes in the spectra due to charge transfer between the Na adlayer and the surface Ga or N atoms.

Abstract: This study investigated the potential of acid-pretreated rice husk ash (RHA) sourced alkaline earth metal silicates for lauric acid (LA) adsorption. The synthesized materials were characterized using BET, FTIR, XRD, EDS, and SEM analyses, demonstrating that metal cation size had a notable effect on surface area, pore structure, crystallinity, and particle aggregation. Magnesium silicate (MS-1.0), with its smaller atomic radius, exhibited the highest surface area and the most porous structure among the samples. Calcium silicate (CS-1.0) displayed a moderate surface area with a mesoporous structure, while strontium silicate (SS-1.0), having the largest atomic radius, exhibited the lowest surface area, a predominantly macroporous structure and the highest degree of particle aggregation. The synthesized alkaline earth metal silicates were tested for LA adsorption performance and compared using the analytical hierarchy process (AHP). CS-1.0 demonstrated the highest LA removal efficiency (59.94% ± 11.24%) and adsorption capacity (8.68 ± 1.60 mmol/g), while MS-1.0 had the lowest removal efficiency (17.64 ± 3.28%) and adsorption capacity (2.60 ± 0.50 mmol/g). Interestingly, the production yield increased from MS-1.0 to CS-1.0 and SS-1.0. Through the AHP method, CS-1.0 was identified as the best-performing adsorbent in this study, considering both adsorption efficiency and production yield with the highest priority value of 0.9603.

Abstract: Waste frying oil (WFO) is a major byproduct of food preparation, containing elevated levels of free fatty acids (FFA), which reduce its potential for reuse in biodiesel production and other applications. This study investigates the use of hydrochloric acid (HCl)-pretreated rice husk ash (RHA) as an adsorbent for removing FFAs, with lauric acid as a model FFA. RHA pre-treated with different HCl concentrations (1 – 5 M) was synthesized and characterized using SEM-EDS and FTIR. SEM analysis revealed that acid treatment improved surface roughness and porosity, while EDS confirmed an increase in silica content, particularly in RHA treated with 4M HCl. FTIR identified key functional groups that contributed to FFA adsorption. Batch adsorption experiments demonstrated the effect of HCl concentration, adsorbent dosage, and initial FFA concentration on adsorption capacity and removal efficiency. The study shows that acid pre-treatment enhances RHA's adsorption properties, offering a potential solution for the sustainable management of WFO and improving its applicability in purification processes.