Nilgün Onursal

Determining the optimal adsorbent dosage remains a critical yet unresolved challenge in adsorption science, as no established mathematical framework directly links adsorbent mass to equilibrium uptake capacity. This study proposes a linear mass–uptake model for the first time, expressed as m/qₑ = (1/qₘ)m + Kₒ/qₘ. The qₘ (mg g⁻ ¹ ) represents the maximum adsorption capacity, and Kₒ (g) denotes the semi-saturation constant—the adsorbent mass required to achieve qₘ/2. A green-synthesized Prunus spinosa silver nanocalcite composite (PSSNCC) was prepared by combining biogenic silver nanoparticles (AgNPs) with nanocalcite and used as the model adsorbent for Ni(II) removal from aqueous solution. The composite was characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and ultraviolet–visible (UV-Vis) spectroscopy. Application of the linear model yielded qₘ = 54.95 ± 0.42 mg g⁻ ¹ and Kₒ = 3.423 ± 0.05 g with an exceptionally high coefficient of determination (R ² = 0.9998). Equilibrium isotherm experiments conducted at 298, 308, and 318 K demonstrated that Ni(II) adsorption on PSSNCC follows the Langmuir model (R ² = 0.986 at 298 K), yielding a maximum monolayer capacity of 70.42 mg g⁻ ¹ . The proposed model eliminates trial-and-error adsorbent dosing, enabling rational prediction of optimal adsorbent quantities for any target uptake, and represents a significant advancement in adsorption process design.

In recent years, researchers prefer to use biomaterials as sorbents in adsorption studies. Orange is a fruit abundantly found in the Mediterranean Basin. In this study, waste orange peel (WOP) was used as an adsorbent because it is cheap and harmless to nature. Nickel is a heavy metal widely used in industry. In parallel with its natural use, it pollutes the environment and harms many living things, especially humans. In this study, the adsorption kinetics of WOP, which is evaluated for the removal of Ni (II) ions from aqueous solutions, was investigated. The aim is to reveal which kinetic model the adsorption is suitable for and whether the adsorption is physical or chemical. Previously, the structure of the adsorbent was elucidated by SEM-EDX, FTIR analysis. The data obtained from the kinetic study carried out at 3 temperatures, 298, 308 and 318 K, were applied to the 3 linear types (types 6, 7 and 8) of the Pseudo-Second Order (PSO) kinetic model, which are the most compatible with the experimental data, namely Pseudo-First Order (PFO), Weber Morris (Intraparticle Diffusion Model) and Elovich models. The obtained constants were compared by tabulating. The constants for this model are 0.9953, 0.9934, 0.9986 for temperatures of 298, 308 and 318 K and type 6, and 0.9953, 0.9934, 0.9988 for type 8, respectively. As a result, when the regression coefficients were examined, it was determined that the nickel adsorption kinetics of this adsorbent was in good agreement with the PSO 6 and type 8 models and the adsorption was chemical in character.

This paper evaluates Malatya clay (MC) for the removal of Ni(II) ions from aqueous solutions. For adsorption efficiency, the impacts of several factors, such as pH, starting metal ion concentration, and contact duration, were examined. The optimal initial Ni(II) ion concentration was determined to be 5 mg/L, the adsorption contact duration was 360 min, and the solution's pH was 6.27. Using scanning electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy, the surface characteristics of Malatya clay were examined. The isotherm data fit the Langmuir isotherm model, indicating chemical adsorption and likely irreversibility of the process, according to the results. At 298, 308, and 318 K, the adsorption capacities of Ni(II) were determined to be 10.267, 11.834, and 12.285 mg/g, respectively. Adsorption kinetic data revealed that the adsorption of Ni(II) metal ions followed the pseudo‐second‐order kinetic model. According to thermodynamic studies, Ni(II) ion adsorption on the MC is spontaneous and endothermic. MC has proven to be an effective and alternative material for the removal of Ni(II) ions from aqueous media due to its excellent removal ability, availability, and low cost, as well as its features such as being able to be used without any chemical treatment and being environmentally friendly.

One of the most significant environmental pollutions is water pollution. Water pollution, which is a problem all over the world, has been increasing recently due to unconscious and contemptuous water usage and will inevitably lead to water wars. In this context, it has become a necessity to reduce water pollution and raise awareness among people. One of the effective and inexpensive methods among the studies on this subject is adsorption. The main purpose of this study is to remove Ni (II) ions from aqueous solutions. For this, mixed type clay was used as adsorber. Clay obtained from the Koçpınar town of Siirt is preferred because it can be obtained easily and it’s cost is low. To determine the characterization of the clay, SEM, XRD XRF and FT-IR analyzes were performed. The results obtained from these analyzes showed that the clay was of mixed type. Pseudo-second-order kinetic models are widely applied to data from most adsorption kinetic studies to describe the adsorption mechanism of adsorbate on adsorbent. In this research, 6 different types of pseudo-second order kinetic equations were applied to values at 298 K temperature. The obtained data were applied to six types of linear equations. R2, K2 and qm values were calculated by creating graphs in the light of abovementioned data. As a result of the obtained data, it was understood that adsorption kinetics comply with type 6 equation at most.