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The present study focuses on the effect of experimental parameters (pH, temperature, gel mass, metal concentration, contact time) on the performance of lead adsorption by polyacrylamide hydrogels. The results obtained showed that the retention of Pb2+ ions is closely linked to these parameters. The adsorbent gels equilibrate with the metal solution after 180 minutes, and the maximum adsorption capacity is 442.31 mg/g. In addition, the adsorption obeys the pseudo-second-order kinetics and Langmuir isotherm. Desorption of the micropollutant retained by the hydrogel was also studied using 0.1 M of HCl solution. The desorption was rapid, and the efficiency exceeded 90% after a contact time of 90 minutes.

Heavy metal pollution poses a great risk for the environment and the human health. Cadmium is among the most common pollutants found in wastewater, known for its great toxicity even in small doses. This work aims to study the removal of cadmium using natural Moroccan clay (MC). The clay was characterized using X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, BET, and SEM. The effects of several experimental parameters on the clay adsorption capacity towards cadmium ions, such as MC dose, initial concentration and contact time, initial pH, and temperature were studied. The kinetic models Pseudo-first order, Pseudo-second order, and Elovich are evaluated to identify the adsorption process. The adsorption mechanism was determined by the use of the adsorption isotherms: Langmuir, Freundlich, and Temkin model. The results show that the heavy metal retention obeys the Pseudo-second order (R²≥0.99). The Langmuir isotherm model provided the best fit (R²≥0.99) to the experimental data for the adsorption of Cd(II) by MC as compared to the Freundlich and Temkin model. The maximum monolayer adsorption capacity of Cd(II), using the Langmuir model equation, is equal to 5.25 mg/g. The adsorption is a spontaneous and an endothermic process characterized by a disorder of the medium.

In this work, we study the elimination of three bivalent metal ions (Cd2+, Cu2+, and Pb2+) by adsorption onto natural illitic clay (AM) collected from Marrakech region in Morocco. The characterization of the adsorbent was carried out by X-ray fluorescence, Fourier transform infrared spectroscopy and X-ray diffraction. The influence of physicochemical parameters on the clay adsorption capacity for ions Cd2+, Cu2+, and Pb2+, namely the adsorbent dose, the contact time, the initial pH imposed on the aqueous solution, the initial concentration of the metal solution and the temperature, was studied. The adsorption process is evaluated by different kinetic models such as the pseudo-first-order, pseudo-second-order, and Elovich. The adsorption mechanism was determined by the use of adsorption isotherms such as Langmuir, Freundlich, and Temkin models. Experiments have shown that heavy metals adsorption kinetics onto clay follows the same order, the pseudo-second order. The isotherms of adsorption of metal cations by AM clay are satisfactorily described by the Langmuir model and the maximum adsorption capacities obtained from the natural clay, using the Langmuir isotherm model equation, are 5.25, 13.41, and 15.90 mg/g, respectively for Cd(II), Cu(II), and Pb(II) ions. Adsorption of heavy metals on clay is a spontaneous and endothermic process characterized by a disorder of the medium. The values of ΔH are greater than 40 kJ/mol, which means that the interactions between clay and heavy metals are chemical in nature.

The adsorption of methyl orange (MO) dye by artificial zeolites beads, used previously in the removal of heavy metal through the ionic exchange process, has been studied. The effect of several parameters such as temperature, MO concentration, and zeolite mass on MO adsorption was tested in order to determinate optimal conditions. All results have shown that the adsorption process was influenced by the studied parameters. The kinetic data concerning the study of temperature effect was modeled through pseudo-first-order and pseudo-second-order to determinate the adsorption mechanism. Thermodynamic parameters were calculated using the Van’t Hoff equation. Also, they have shown that the studied process has an endothermic, stable and spontaneous nature.

The present work aims the elimination of an organic dye Methylene Blue (MB) by adsorption on the polyacrylamide (PAAM) hydrogel. Several experiments series were then carried out in order to study the influence on the adsorption capacity of certain parameters such as the mass of the adsorbent, the pH, the contact time, the initial dye concentration and the temperature. The maximal capacity is 1620 mg/g it was obtained at T = 25°C, pH = 6, [BM] = 200 ppm and 0.013g of the adsorbent. The adsorption kinetics of the dye on the support is well described by the first-order model. The adsorption isotherms of the adsorbent/adsorbate systems studied are satisfactorily described by the Langmuir mathematical model. On the other hand, the thermodynamic study revealed that adsorption is spontaneous and endothermic.

Coriandrum Sativum seeds (CSS), were tested as a new eco-friendly adsorbent of copper ions from aqueous solutions. Hence, the effect of the most influencing experimental parameters such as initial concentration of Cu (II) and the temperature was studied upon the adsorption process in order to use its results in following studies. Lagergren pseudo-first-order, pseudo-second-order, and Intraparticle diffusion models were used to describe the biosorption kinetics. The adsorption process was also analyzed by Langmuir, Freundlich and Temkin models and the maximum monolayer biosorption capacity of CSS was found to be 33,5 mg. g −1 by using the Langmuir model. So as to investigate the thermodynamic properties of the adsorption process, the Gibbs free energy ( Δ G°), enthalpy ( Δ H°), and entropy ( Δ S°) values in the temperature range of 25-55 C ° were also calculated in order to conclude the process characteristics. SEM and EDAX analysis were effectuated in order to study the surface morphology of CSS before and after the adsorption process.

The present work aimed to investigate the potential power of coriander seeds to remove dyes from contaminated solutions. The characterization of the adsorbent before and after the adsorption of indigo blue and methyl orange have shown that they have a porous structure rich in active sites, which constitutes a very important seat to fix organic pollutants. Then, the study of the adsorption of indigo blue and methyl orange by CS was highlighted through parametric study, thermodynamic study, mathematical modelling and spectroscopic analysis. The optimal contact time for the biosorption performance of CS are 20 and 35 min for IB and MO, respectively. Then, the biosorption capacity of coriander seeds powder increases from 9 to 124 mg.g−1 and from 8.23 to 42 mg.g−1 for IB and MO, respectively. Further, The elimination yield values of the biosorption capacity of coriander seeds are 92 and 83 % for IB and MO, respectively. Further, global quantum chemical descriptors (GQCDs) namely EHOMO, ELUMO, energy gaps, electronegativity, hardness, electrophilicity, fractions of electron transferred between cellulose that is the major component of coriander seeds and both of studied dyes IB and MO were performed through density functional theory (DFT) method at M06-2x functional with 6-311G(d,p) basis set and were also examined and more discussed. All the obtained results were in a good correlation with experimental, spectroscopic, mathematical modelling and thermodynamic studies.

The adsorption of chromium ions Cr3+ using two forms of a superabsorbant polymer PANa from aqueous solution was investigated. On one hand the equilibrium pH with the distilled water and the pH of point of zero charge have been studied in order to characterize the acid-base behavior of both of PANa forms. On the other hand, the effect of contact time between PANa and the metallic solution and stirring speed of aqueous solution on the adsorption rate were established to highlight the importance of PANa as an efficient adsorbent of chromium ions Cr3+.

The adsorption of copper ions Cu2+ by Coriandrum Sativum seeds (CSS) from aqueous solution was studied in order to highlight the importance of coriander seeds as a potential tool in the treatment of wastewaters containing heavy metals. The kinetic studies of adsorption of Cu (II) were discussed using the spectroscopic technique “Inducting Coupled Plasma” (ICP). The effects of initial copper ion concentration and contact time were determined. All results show that coriander seeds have, over their culinary and medicinal benefits, a significant adsorbent power of copper ions.