Papers by Keyword: Adsorption Isotherm

Abstract: The corrosion inhibition on mild steel by eco-friendly paint produced from Mangifera indica leaves extract was carried out using the weight loss and potentiodynamic polarization methods. Central Composite Design (CCD) in Response Surface Methodology (RSM) was used for the design of experiment for the determination of corrosion inhibition efficiency, corrosion rate, and statistical analysis of the experimental results. Corrosion protection paint was formulated, and its efficacy was tested in a hydrochloric acid medium. The surface morphology of the mild steel sample was studied using the scanning electron microscopy (SEM). The corrosion inhibition efficiency of the paint for weight loss and potentiodynamic polarization methods is 83.68 and 99.49 %, respectively. The activation energy for corrosion process with coated mild steel is 26.47 J/mol K, which is higher than the value of 16.89 J/mol K obtained for uncoated mild steel, indicating that the adsorption process is physisorption. The enthalpy change is 23.96 kJ/mol. The positive value indicates that heat is absorbed from the environment. The entropy change is-180 J/mol K, implying that the activation energy complex is the rate determining step representing association rather than dissociation. Langmuir adsorption isotherm was found to be the best fit model. It was concluded from the study that the formulated paint has a high potential for commercialisation and industrial applications.

Abstract: This study examined the corrosion inhibition characteristics of Launaea taraxacifolia on mild steel in 1M H₂SO₄ solution, considering the demand for environmentally benign and effective corrosion inhibitors in acid media. The work aimed at elucidating the adsorption behavior, inhibition mechanism, and thermodynamic properties of L. taraxacifolia. Gravimetric and potentiodynamic techniques were employed in assessing inhibitor performance for variations in inhibitor concentrations (0.3%–1.2% W/V), immersion time (10–60 minutes), and temperature (303K–323K). The results indicated that corrosion rates increased with temperature, showing that the inhibitory process is dependent on the adsorption of L. taraxacifolia onto the steel surface. Adsorption obeyed Freundlich and Temkin isotherms, and the calculated heat of adsorption was -11 kJ/mol, which indicated physical adsorption. The presence of key phytochemicals, aromatic compounds, and heteroatoms in the inhibitor played an important role in the process, making it a mixed-type inhibitor. The maximum inhibition efficiency of 97.78% was recorded at higher inhibitor concentrations and longer immersion times. The weight loss measurements were within the range of 0.001g to 0.038g across the temperatures. This study illustrates the potential of L. taraxacifolia as a green inhibitor, evidenced by its thermodynamic and kinetic properties. It concludes that L. taraxacifolia might serve as a good substitute for synthetic inhibitors, especially in those industries where environmental considerations are essential.

Abstract: Magnetic biochar derived from various residual agricultural wastes have been widely studied due to their abundance, low cost, and minimal environmental impact. Pecan nutshell (Carya illinoinensis) residuals were incorporated with γ-Fe₂O₃, transforming them into magnetic adsorbents. The effect of particle size (granular: 0.38-0.7 mm; powder: 0.15-0.38 mm) and pyrolysis temperature (500 °C and 650 °C) were investigated for their influence on adsorption capacity of arsenic and fluoride in aqueous solutions. Our findings showed that finely powdered magnetic biochar produced at 650 °C (PMPH-650) exhibited the highest removal efficiency (99.09%) and adsorption capacity (4.925 mg/g) for arsenic compared to other materials. The arsenic adsorption isotherm followed both Langmuir and Freundlich models well. The kinetics of fluoride adsorption fit the Elovich equation, suggesting chemisorption and chemical bond formation. XRD and FTIR analyses confirmed the presence of the γ-Fe₂O₃ phase. SEM/EDX and FTIR analyses confirmed the presence of arsenic on the biochar surface after the adsorption. This research paves the way for using magnetic biochar derived from pecan nutshell as a cost-effective and eco-friendly approach for arsenic and fluoride remediation in water.

Abstract: Graphene oxide has drawn attention globally as it emerged as a promising adsorbent material with enhanced adsorption of environmental pollutants due to its eco-friendly attributes, high surface area, and cost-effectiveness for mass production. This economical solution is a promising and potentially transformative approach to heavy metal removal, contributing to a cleaner and more sustainable future. In this study, unmodified and modified graphene oxide were examined for the removal of copper (II) ions in an aqueous solution. Modified Hummer’s method was utilized to synthesize the graphene oxide. The synthesized graphene oxide was then modified with N- trimethoxysilylpropylethylenediaminetriaceticacid (EDTA-silane), resulting in EDTA-modified graphene oxide (EGO). Batch adsorption tests were done for both adsorbents in order to determine the effects of various factors, such as pH, adsorbent dosage, and contact time. Additionally, in order to describe the adsorption behavior of the adsorption system, it was further fitted to isotherm and kinetic adsorption models. Results of adsorption study showed optimum adsorption for copper (II) ions was achieved at pH = 7, contact time = 45 min, and adsorbent dosage of 5 mg and 4 mg of unmodified graphene oxide (GO) and modified graphene oxide (EGO), respectively. The fundamental mechanism of both adsorbents was best explained by Langmuir isotherm model and the pseudo-second-order model, indicating that the adsorption system followed chemisorption. The adsorption capacity and maximum removal of copper (II) ions was 672.22 mg/g and 78.41% for GO, and 729.11 mg/g and 89.94% for EGO. The latter suggested that graphene oxide treated with EDTA-silane (EGO) has the higher capacity to adsorb copper (II) ions.

Abstract: The menace of the disposal of agricultural wastes and water contamination is on the increase. Thus, the need to find a way to recycle these agriculture wastes and make water safe for use. In this study, raw Peanut shell (PSH) and Carbonized Peanut Shell (CPSH) were used as biobased adsorbents in the decontamination of methylene blue (MB) dye from solution. The prepared materials were characterized by SEM, FTIR, XRD, and BET surface area analysis. The batch adsorption method was selected in the MB removal process to maintain adsorbent dosage and dye concentration. The surface area was increased from 1.03 to 34.96 m²/g. also the pore diameter reduced form macropore (93 nm) to micropores (2.39 nm) after carbonization. The CPSH has an adsorption capacity of 104 mgg^-1 and about 90% removal of the 50 mg/L MB with 40 mins at a pH of 6.5. The pseudo-second-order kinetic model best suits the adsorption performance of the CPSH adsorbent. Also, the dye adsorption procedure onto the PSH corresponds to the Langmuir isotherm while the CPSH best fitted with the Freundlich isotherm. This study presents PSH as an alternative resource for the preparation of a cheap and efficient adsorbent from agricultural waste for the removal of laden dye.

Abstract: In the process of incorporating adsorption with thermal desalination, adsorbents are important because they increase the water vapour uptake rate, and this would yield more desalinated water over a short period. Therefore, they are important and the key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle are thermo-physical properties, surface characteristics and water vapor uptake capacity. The best adsorbent is used as the adsorbent-refrigerant pair and is driven at 50 oC to 85 oC by low-temperature heat sources. When the unsaturated adsorbent is exposed to vapour in the evaporator, the uptake of vapor is accelerated by the high affinity of the water molecules to the silica gel pores. Likewise, when the same adsorbent is heated thermally, the water vapor molecules are removed or desorbed from the adsorbent pores to the cooler surfaces of the condenser tubes, producing high-grade water during the phase. Key words: Desalination; Porosity; Adsorption isotherm; Geometric parameters. Sorption Phenomenon

Abstract: The corrosion inhibition effect of Cocos nucifera (CN) surfactant inhibitor, has been inspected on 316L steel in 5 M HCl and H₂SO₄ solutions by weight loss (WL) method. The results revealed that the presence of alkanols, glycosides, steroids and terpenoids in CN surfactant supported the inhibitor by retarding corrosion effect to give an optimum inhibition efficiency of 93.71% in HCl and 89.66% in H₂SO₄ solutions after 504 h. Also, the regression values for both acidic solutions were close to unity after obeying Langmuir isotherm adsorption mechanism with 0.9971 for HCl and 0.9882 for H₂SO₄ solution. The result confirms that CN surfactant inhibitor performed better in HCl solution than in H₂SO₄ solution. Keywords: Corrosion inhibitor; active components; austenitic 316L material; weight loss method; adsorption isotherm.

Abstract: The barium oxide impregnated iron(III) oxide (BaO/Fe₂O₃) adsorbent was synthesized by an ultrasonic-assisted method. The adsorbent was calcined at 200-500 °C and its adsorption capacity was measured. The ultrasonic-assisted synthesis generated well-dispersed of BaO on Fe₂O₃ by giving none of the BaO peaks were observed through the XRD pattern. The most efficient adsorbent of BaO/Fe2O₃200 was calcined at 200 °C with adsorption capacity for physisorption and chemisorption of 5.01 and 88.81 mg/g respectively. Besides other carbonate species, it was believed the presence of the hydroxyl group could enhance the sorption by forming bicarbonate upon CO₂ chemisorption. It is also possessed a lower desorption range compared to BaO and Fe₂O₃ alone. The experimental CO₂ adsorption isotherm at 25 °C fit better with the Freundlich isotherm model. It implies a favorable adsorption process with multilayer adsorption occurs onto the heterogeneous surface.

Abstract: This paper presents an alternative utilisation of sago barks from the sago industry. In this study, a sago bark-derived magnetic adsorbent was developed by impregnation with ferric chloride hexahydrate (FeCl₃H₂O) and carbonisation method. The potential of the sago bark-derived magnetic adsorbent to remove lead ion (Pb²⁺) and copper ion (Cu²⁺) from aqueous solution was assessed in a batch system. Adsorption experiments were performed as a function of initial concentration (5.0 – 15.0 mg/L). The magnetic adsorbent displayed good ferromagnetic property which aids the separation of the adsorbent after the decontamination process. The magnetic adsorbent was characterised by Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy embedded with an Energy Dispersive X-ray Spectrometer (SEM-EDX). The FT-IR spectra analysis revealed the surface functional groups of the magnetic adsorbent are C−O−C, C−OH, C− H, −C−C−O, Fe-O, O-H, and C-O. The maximum monolayer adsorption capacities were discovered to be 172.414 and 12500 mg/g for lead and copper ions, respectively. The batch adsorption isotherms were analysed using Langmuir, Freundlich, Jovanovic and Temkin isotherm models. The experimental data perfectly fitted with Langmuir isotherm modelling. The results indicated that the sago bark-derived magnetic adsorbent potentially to be an alternative in replacing more high-priced adsorbents for its application in heavy metal ions removal.

Abstract: Surface modification of Fe2O3 by adding BeO was synthesized and calcined at different temperatures of 200-600 °C. The adsorbents were characterized by using XRD, N2 adsorption-desorption isotherm prior to performing CO2 adsorption and desorption studies. The CO2 adsorption data were analyzed using adsorption isotherm models such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich. BeO/Fe2O3-300 that calcined at 300 °C showed the most efficient adsorbent with physisorption and chemisorption were measured at 5.85 and 45.88 mg/g respectively. The CO2 adsorption notably best fitted with Freundlich isotherm with R2 = 0.9897 and calculated adsorption capacity closest to experimental data. This implies the CO2 adsorption process was governed by multilayer adsorption on the heterogeneous surface of the adsorbent. The mean free energy of adsorption (E=3.536 kJ/mol) from Dubinin-Radushkevich and heat of adsorption (bT=3.219 kJ/mol) from the Temkin model support that the adsorption process is physical phenomena.