Papers by Keyword: Isotherm

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: Layered double hydroxides (LDHs) have achieved remarkable attention these days for their promising applications ins water remediation, owing to their excellent anion exchange capacity and robust structured modification possibility. In this study, Mg-Al LDH of different metal ion ratio (2:1, 3:1 and 4:1) were synthesized by co-precipitation and urea hydrolysis method. The as synthesized LDHs were characterized by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDX). A series of Cr (VI) removal efficacy were studied by batch adsorption method. The results indicated that removal of Cr (VI) from aqueous solution is pH dependent and a maximum Cr (VI) removal was achieved at pH 5. The Mg-Al LDH containing 2:1 metal ion ratio showed highest adsorption capacity irrespective of method of preparation. The equilibrium adsorption data are well supported by Langmuir isotherm (LI) and maximum loading capacities for Cr (VI) removal were 37.26 and 55.26 mg g⁻¹ for LDH MAC-21 and MAU-21, respectively suggesting that LDH obtained by urea hydrolysis method have shown better performance. The equilibrium kinetics data are well supported by pseudo-second order model for all LDH tested samples.

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: One kind of heavy metal that comes from industrial waste is Cr (VI), which is obtained from steel, textile, tanning, photography, dyes, explosives, matches, and fuel mobilization waste. Cr (VI) is a carcinogen and extremely hazardous to both people and animals. In Indonesia, bentonite is a raw material that is abundantly available. This study aims to investigate the effects of varying adsorbent doses on the properties, % removal, isotherms, and kinetics of adsorption of Cr (VI) from aqueous solution. Adsorbent doses ranged from 10 g/L to 30 g/L for 0–80-minute contact periods. morphological analysis of bentonite using a scanning electron microscope (SEM). Features of bentonite were tiny lumps of varying sizes and the absence of pores. 96.5% is the optimal elimination of Cr (VI). The morphological analysis of bentonite using a scanning electron microscope (SEM). Features of bentonite were tiny lumps of varying sizes and the absence of pores. When using a dose of 20 g/L and a 60-minute duration, the maximum elimination of Cr (VI) is 96.5%. Isotherms follow Langmuir and kinetics fit to first order. These findings demonstrate that bentonite is a valuable material for future development and is effective at removing Cr (VI) from aqueous solutions.

Abstract: The aim of the study is to research of the adsorption properties of heavy metal ions Pb²⁺, Cd²⁺ and Ni²⁺ from industrial wastewater. For the adsorption of heavy metal ions, natural clinoptilolite was used, which belongs to the Ai-Dag deposit of the Tovuz-Kazakh region of Azerbaijan. Isotherms and kinetic curves of adsorption of heavy metal ions Pb²⁺, Cd²⁺ and Ni²⁺ were determined. The dependence of the adsorption of heavy metal ions on the pH value is also shown. It was revealed that the separation process proceeds more intensively at pH values ​​of 5-6. It has been established that the maximum adsorption capacity of the clinoptilolite adsorbent for adsorption of Pb²⁺, Cd ²⁺ and Ni²⁺ ions is 7.5, 6.7 and 5.9 mmol/g, respectively.

Abstract: In this study, isotherm and kinetic adsorption of malachite green (MG) using coal fly ash (CFA) as the adsorbent was investigated. This study aimed to examine the character of CFA analyzed by Atomic Absorption Spectrophotometry (AAS), Fourier-Transformed Infra-Red (FTIR), and X-Ray Diffraction (XRD) analysis. In addition, the adsorption of MG on CFA was also studied, including the effect of solution pH, adsorbent mass, contact time, and concentration of malachite green on the adsorption process. From the experimental data, the kinetic parameters isotherms and energy of the adsorption were determined. Kinetic study showed that the kinetic adsorption of MG on CFA fit well the Ho and McKay's pseudo-second-order, with an adsorption rate constant (k₂) of 0.0377 g mg^-1 min^-1. Furthermore, the Langmuir isotherm model was the most suitable model to describe adsorption. Changes in the standard Gibbs free energy calculated from equilibrium constant (K_L) at room temperature (303 K) showed that the adsorption process occurred spontaneously through chemical interaction (chemisorption) and most probably formed a monolayer on the surface of the adsorbent.

Abstract: The kinetic and isotherm study on the adsorption of crystal violet (CV) on coal fly ash (CFA) has been studied. Before being used as an adsorbent, CFA was characterized with AAS, XRF, FT-IR, and XRD to determine the mineral components in CFA. The adsorption study of crystal violet in water with CFA includes the effects of solution pH, mass adsorbent, crystal violet concentration, and contact time on the adsorption process. The pseudo-second-order kinetic model best expressed the crystal violet adsorption behavior on CFA with the rate constant (k) of 1.24×10^-1 g mg^-1 min^-1. The Langmuir isotherm model was found to be the best model to describe the adsorption, with a maximum adsorption capacity of 10.14 mg g^-1 at room temperature. Based on the value of adsorption energy as well as the best isotherm model, the adsorption of CV on CFA forms a monolayer and can be classified as chemisorption.

Abstract: Herein, for the first time, we investigate the adsorption performance of nanoZn benzenedicarboxylate metal-organic framework (nanoMOF-5) as an efficient adsorbent material for Cr (VI) decontamination from polluted water. The synthesized Zn MOF-5 was fully characterized via FT-IR, XRD, HRTEM, BET, and TGA techniques. Moreover, the prepared Zn MOF-5 revealed a prominent surface area of 1169.32 m² g^-1, demonstrating its ability to be utilized as a capable adsorbent material. The adsorption profile of Cr (VI) onto the fabricated Zn MOF-5 was performed against the various parameters such as contact time, dosage, and initial Cr (VI) concentration. The optimum dosage from the Zn MOF-5 for 81.03% adsorption of 25 ppm Cr (VI) was 0.5 g L^-1 at pH=7 after 15 min. The Cr (VI) decontamination performance of the synthesized Zn MOF-5 recorded the maximum monolayer adsorption capacity of 91.22 mg/g. These data demonstrated that the synthesized nanoZn MOF-5 is a promising adsorbent material for the removal of Cr (VI) from wastewater. Keywords: Zinc Metal-Organic Framework (MOF-5), Cr (VI) Decontamination, Isotherm and Kinetics, Recyclability.

Abstract: The bioconversion of biomass-based feedstocks to carbonaceous adsorbents is considered a cost-effective and environmentally friendly route for pollutant removal from wastewater. This study focused on preparing biochar from the pyrolysis of digestate of anaerobically processed rice straw, namely digested rice straw biochar (DRSB). The DRSB material was employed as an adsorbent to eliminate methylene blue (MB) from aqueous solutions. The adsorption mechanism was illustrated regarding DRSB characterization via Scanning Electron Microscopy (SEM) related surface morphology and Fourier Transform Infrared Spectroscopy (FTIR) associated surface functional groups. The effect of adsorption factors (solution pH, initial dye concentration, contact time, and adsorbent dosage) on the MB removal efficiency was investigated. The optimum adsorption pH value was 7, achieving MB removal efficiency of 92.98% using adsorbent dosage = 6 g/L and initial MB concentration = 20 mg/L, within 60 min. The experimental data fitted well onto the Langmuir (R²= 0.94) and Freundlich (R²= 0.99) adsorption isotherm models. The Langmuir maximum adsorption capacity (Q_m) was estimated as 18.90 mg/g and the Freundlich intensity parameter (1/n) was derived as 0.58, indicating the favorability of MB adsorption onto DRSB. Adsorption kinetics were also tested and explained using pseudo-first-order and pseudo-second-order models, suggesting the contribution of both chemisorption and physisorption mechanisms for MB uptake. The synthesis of DRSB revealed a feasible economic adsorbent with a total cost of 0.3022 US$/kg. This study depicted that the utilization of digested residues resulting from the anaerobic digestion of agricultural wastes for preparing biochar adsorbent would be considered for the real application of dye-laden textile wastewater treatment.