Cosmin Vancea

This research evaluates the feasibility of using a lignocellulosic biosorbent prepared from mature leaves of Asplenium scolopendrium (produced through simple mechanical processing of the leaves, without applying any chemical modification or heat treatment) for the removal of methylene blue from water. Before and after adsorption the material was characterized using SEM technique and color analysis. Subsequently, the adsorption behavior was analyzed by examining equilibrium, kinetic, and thermodynamic aspects of the process. The equilibrium data were best represented by the Sips isotherm model, while the adsorption rate followed the Avrami model. Thermodynamic evaluation indicated that the retention of the dye occurs predominantly through a physical adsorption mechanism, while a minor contribution from chemisorption may be present, slightly enhancing the overall dye uptake. Process optimization was performed using the Taguchi experimental design, which also allowed the identification of the most significant operational variable. In addition, analysis of variance (ANOVA) was applied to quantify the contribution of each factor affecting dye removal efficiency. Among the investigated variables, time showed the strongest influence (72.65%), whereas temperature had a negligible effect (1.33%). The maximum adsorption capacity reached 174.1 mg/g, surpassing the performance of several comparable biosorbents reported in the literature. Overall, the findings demonstrate that Asplenium scolopendrium (hart’s-tongue fern) leaves represent an inexpensive, sustainable, and efficient material for eliminating methylene blue from aqueous solutions.

The present study investigates the potential of a new lignocellulosic adsorbent material obtained from mature coltsfoot (Tussilago farfara) leaves for the removal of methylene blue from aqueous solutions. The material was obtained after minimal processing of the leaves, without chemical or thermal treatment. The material was first characterized using several specific techniques (FTIR, color analysis). Then, the mechanism of the adsorption process was investigated through studies related to adsorption equilibrium, kinetics, and thermodynamics. The adsorption process is described by the Sips isotherm and the general kinetic model, while the thermodynamic parameters suggest that physical adsorption is the primary mechanism responsible for dye retention. The Taguchi method was used to optimize the adsorption conditions and to identify the most influential controllable factor. ANOVA was used to calculate the percentage contribution of each controllable factor to the dye removal efficiency. pH had the greatest influence on the process (87.78%), while temperature had the least effect (0.16%). The maximum adsorption capacity determined was 278.1 mg/g, being higher than other similar adsorbents. All the results show that coltsfoot (Tussilago farfara) leaves are a very cheap, environmentally friendly, and effective adsorbent for the removal of methylene blue dye from aqueous solutions.

In this study, chitosan (Chi) functionalized with the amino acid serine (Ser) was synthesized for the adsorption-based recovery of Pt(IV) from aqueous solutions. To identify the active functional groups of the amino acid and the support material, the synthesized adsorbent was characterized using SEM, FT-IR, and EDX analyses, and its point of zero charge (pH_PZC) was determined. Static and dynamic adsorption studies were conducted to optimize process parameters. Under static conditions, equilibrium studies established the maximum Pt(IV) concentration that could be adsorbed onto Chi–Ser, as well as its maximum adsorption capacity. At pH > 4, with an S-L ratio of 0.1 g:25 mL Pt(IV) solution, a contact time of 90 min, and a temperature of 298 K, the maximum adsorption capacity reached 7.23 mg/g. The adsorption process was best described by the Sips isotherm. The Taguchi method was employed to optimize static adsorption conditions. The Clark equation most accurately modeled the adsorption process under dynamic conditions. Additionally, multiple adsorption–desorption cycles evaluated the adsorbent’s reusability.

Given the ever-increasing demand for gallium(III) as a crucial precursor in the fabrication of advanced materials, there arises an imperative to devise efficient recovery processes from primary and secondary sources. In the present investigation, the retrieval of gallium(III) from aqueous solutions through the mechanism of adsorption was investigated. Materials with superior adsorbent properties play an important role in the dynamics of the adsorption process. To enhance these properties, select materials, such as Amberlite-type polymeric resins, are amenable to functionalization through impregnation with extractants featuring specialized active groups, designed for the selective recovery of metal ions—specifically, Ga(III). The impregnation method employed in this study is the Solvent-Impregnated Resin (SIR) method, utilizing the amino acid DL-valine as the extractant. The new material was characterized through Scanning Electron Microscopy (SEM), Elemental Analysis via X-ray energy-dispersive spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) to elucidate the presence of the extractant on the resin’s surface. Concurrently, the material’s pH_PZC was determined. The adsorptive prowess of the synthesized material was investigated through kinetic, thermodynamic, and equilibrium studies. The influence of specific parameters in the adsorption process—namely, pH, contact time, temperature, and Ga(III) initial concentration—on the maximal adsorption capacity was determined. The optimal adsorption conditions were established using the Taguchi method.

The main objective of this study was to optimize the adsorption process of methylene blue on a natural, low-cost adsorbent, Leonurus cardiaca L. biomass powder, in order to maximize dye removal efficiency from aqueous solutions. For this purpose, the Taguchi method was used based on an L₂₇ orthogonal array design considering six controllable factors at three levels. The percentage contribution of each factor was computed using analysis of variance (ANOVA). The optimal adsorption conditions were established. The experimental data from equilibrium and kinetic studies were modelled using specific equilibrium isotherms and kinetic models. Thermodynamic parameters were calculated in order to determine the main adsorption mechanism. The obtained results showed that the ionic strength is the factor that most influences dye adsorption (percentage contribution 72.33%), whereas the adsorbent dose had the least impact. The Sips isotherm and the general kinetic model most accurately characterized the process. The maximum adsorption capacity 103.21 (mg g⁻¹) indicated by the Sips isotherm and the equilibrium time (40 min) were better compared to the values obtained for other bio-adsorbents used for methylene blue adsorption. The main mechanism involved in the adsorption is physisorption, while chemisorption only contributes marginally to the process.

The remediation of arsenic contamination in potable water is an important and urgent concern, necessitating immediate attention. With this objective in mind, the present study investigated arsenic removal from water using batch adsorption and fixed-bed column techniques. The material employed in this study was a waste product derived from the treatment of groundwater water for potable purposes, having a substantial iron composition. The material’s properties were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FT-IR). The point of zero charge (pH_PZC) was measured, and the pore size and specific surface area were determined using the BET method. Under static conditions, kinetic, thermodynamic, and equilibrium studies were carried out to explore the influencing factors on the adsorption process, namely the pH, contact time, temperature, and initial arsenic concentration in the solution. It was found that the adsorption process is spontaneous, endothermic, and of a physical nature. In the batch adsorption studies, the maximum removal percentage was 80.4% after 90 min, and in a dynamic regime in the fixed-bed column, the efficiency was 99.99% at a sludge:sand = 1:1 ratio for 380 min for a volume of water with arsenic of ~3000 mL. The kinetics of the adsorption process conformed to a pseudo-second-order model. In terms of the equilibrium studies, the Sips model yielded the most accurate representation of the data, revealing a maximum equilibrium capacity of 70.1 mg As(V)/g sludge. For the dynamic regime, the experimental data were fitted using the Bohart–Adams, Thomas, and Clark models, in order to establish the mechanism of the process. Additionally, desorption studies were conducted, serving as an essential step in validating the practical applicability of the adsorption process, specifically in relation to the reutilization of the adsorbent material.

In this work, a new lignocellulosic adsorbent was obtained and tested for crystal violet dye removal from water. The material was obtained from hart’s-tongue fern (Asplenium scolopendrium) leaves after minimal processing, without chemical or thermal treatment. The surface of the material was characterized using a variety of techniques, including FTIR, SEM, and color analysis. The effect of various factors on the adsorption capacity was then investigated and discussed. The kinetic and equilibrium studies showed that the general-order kinetic model and the Sips isotherm are the most suitable to describe the adsorption process. The equilibrium time was reached after 20 min and the maximum calculated value of the adsorption capacity was 224.2 (mg g⁻¹). The determined values for the thermodynamic parameters indicated physical adsorption as the main mechanism involved in the process. The Taguchi method was used to optimize the adsorption conditions and identify the most influential controllable factor, which was pH. ANOVA (general linear model) was used to calculate the percentage contribution of each controllable factor to dye removal efficiency. Analysis of all the results shows that hart’s-tongue fern (Asplenium scolopendrium) leaves are a very inexpensive, readily available, and effective adsorbent for removing crystal violet dye from aqueous solutions.

The present study aimed to investigate the potential of a new lignocellulosic biosorbent material derived from mature leaves of sour cherry (Prunus cerasus L.) for removing methylene blue and crystal violet dyes from aqueous solutions. The material was first characterized using several specific techniques (SEM, FTIR, color analysis). Then, the adsorption process mechanism was investigated through studies related to adsorption equilibrium, kinetics, and thermodynamics. A desorption study was also performed. Results showed that the Sips isotherm provided the best fit for the adsorption process of both dyes, with a maximum adsorption capacity of 168.6 (mg g⁻¹) for methylene blue and 524.1 (mg g⁻¹) for crystal violet, outperforming the capacity of other similar adsorbents. The contact time needed to reach equilibrium was 40 min for both studied dyes. The Elovich equation is the most suitable model for describing the adsorption of methylene blue, while the general order model is better suited for the adsorption of crystal violet dye. Thermodynamic analyses revealed the adsorption process to be spontaneous, favorable, and exothermic, with physical adsorption involved as the primary mechanism. The obtained results suggest that sour cherry leaves powder can be a highly efficient, eco-friendly, and cost-effective adsorbent for removing methylene blue and crystal violet dyes from aqueous solutions.

In this work it was studied the removal of copper ions from wastewater by adsorption on oak wood ash and the effect of the ash resulting from adsorption process as a soil amendment. The process variables such as pH, contact time and adsorbent dose were optimized for maximum Cu2+ removal. It was establishing the mathematical correlation between this factors and the metal ions removal efficiency using specific 3D software. Adsorption process is described by Freundlich isotherm and pseudo-first order kinetic model. The effect of the wood ash, previously used as adsorbent, as soil amendment was studied using barley crop, Hordeum vulgare L. The values of the specific parameters: germination percent, plant average length, biomass and relative growth rate proving the beneficial effect of the use of wood ash (resulted from the adsorption process) on plant growth.

This paper presents an alternative way to recycle cathode ray tube glass waste, together with fly ash and kaolin, into new glass ceramic materials. The samples were obtained using three firing temperatures: 700, 800, and 900 °C. The effect of the fly ash/CRT waste ratio upon the materials’ firing shrinkage, apparent density, apparent and total porosity, chemical stability, and compression strength was investigated. The firing shrinkage used as a dimensional stability parameter, a firing shrinkage range between 2.19–8.18%, was positively influenced by the waste mix amount. The apparent density of the obtained materials is positively affected by the heat treatment temperature, rising from 2.09 to 2.93 (g·cm⁻³), while the apparent porosity decreases with the increase of the firing temperature from 6.08 to 2.24 %. All the studied glass ceramics show very good chemical stability and complete immobilization of the Pb²⁺ and Ba²⁺ ions in the glass ceramic matrix. The compression strength of the sintered materials ranges between 1.42–11.83 (N·mm⁻²), being positively influenced by the kaolin amount and negatively influenced by porosity. The obtained results confirm the viability of the proposed alternative to use CRT waste and fly ash together with kaolin to obtain glass ceramic materials that can be used for outdoor paving applications.