This article investigated the kinetic studies of thorium adsorption from an aqueous solution with graphene oxide functionalized with aminomethyl phosphonic acid (AMPA) as an adsorbent. First, the AMPA-GO adsorbent was characterized using TEM, XRD, and FTIR methods. Experiments were performed in two batch and continuous modes. In batch mode, adsorption kinetics were studied in different pH (1-4), temperature (298-328 K), initial concentration (50-500 mg L-1), and dosages (0.1-2 g L-1). The results showed that thorium adsorption kinetic follows pseudo-first-order kinetic model and that the adsorption reaction is endothermic. The maximum experimental adsorption capacity of thorium ions was observed 138.84 mg g-1 at a pH of 3, adsorbent dosage of 0.5 g L-1, and a temperature of 328 K. The results showed that AMPA-GO adsorbent can be used seven times with an acceptable change in adsorption capacity. In continuous conditions, the effect of feed flow rate (2-8 mL min-1), initial concentration (50-500 mg L-1), and column bed height (2-8 cm) was investigated. The continuous data was analyzed using the Thomas, Yoon-Nelson, and Bohart-Adams models. The experimental data of the column were well matched with the Thomas, and Yoon-Nelson models. The research results showed that the use of functionalized graphene oxide adsorbents has a great ability to remove thorium from aqueous solutions.

Pomelo, Citrus maxima, peel was chemically modified with lime water and then loaded with Fe(III) to develop anion exchange sites for effective sequestration of As(V) from water. Biosorbent characterizations were done by using FTIR, SEM, XRD, EDX, and Boehm\'s titration. The batch biosorption studies were carried out at various pHs using modified and non-modified biosorbents and optimum biosorption of As(V) occurred at acidic pH (3.0-5.0) for both the biosorbents. A kinetic study showed a fast biosorption rate and obtained results fitted well with the pseudo-second-order (PSO) model. When isotherm data were modeled using the Langmuir and Freundlich isotherm models, the Langmuir isotherm model fit the data better and produced maximal As(V) biosorption capacities of 0.72 ± 03, 0.86 ± 06, and 0.95 ± 05 mmol/g at temperatures 293± 1K, 298± 1K and 303± 1K, respectively. Desorptionof As(V) was effective using 0.1 M NaOH in batch mode. Negative values of ΔG° for all temperatures with positive ΔH° confirmed the spontaneous and endothermic nature of As(V) biosorption. The existence of co-existing chloride (Cl-), nitrate (NO3 -), sodium (Na+), and calcium (Ca2+) showed insignificant interference whereas a high concentration of sulphate (SO4 2-) and phosphate (PO4 3-) significantly lowered As(V) biosorption percentage. Arsenic concentrations in actual arsenic polluted groundwater could be reduced to the WHO drinking water standard (10 μg/L) by using only 1 g/L of investigated Fe(III)-SPP. The dynamic biosorption of As(V) in a fixed bed system showed that Fe(III)-SPP was effective also in continuous mode and different design parameters for fixed bed system were determined using Thomas, Adams-Bohart, BDST, and Yoon-Nelson models. Therefore, from all of these results it is suggested that Fe(III)-SPP investigated in this study can be a potential, low cost and environmentally benign biosorbent material for an effective removal of trace amounts of arsenic from polluted water.

Industrial waste, for instance, textile effluents when released into the ecological system without first being treated or with inappropriate levels of treatment, can lead to serious issues deteriorating the environment and human health. Moreover, solid waste from various industries has also become a major issue due to massive urbanization. For instance, the waste from the metal industry has been rapidly increasing such as Jarosite which has various metals, metal oxides, and silica in its composition. Therefore, Jarosite was utilized as an adsorbent for the adsorption of anionic Congo red (CR) and cationic Methylene blue (MB) dyes from aqueous solutions. The processed adsorbent sample was characterized by BET, XRD, SEM, EDS, FTIR, and XPS techniques. The effects of initial dye concentration, pH, adsorbent dose, temperature, and contact time were examined. The metal industry waste is used as a low-cost abundant adsorbent with great potential for adsorption ability to remove the CR (97.5%) and MB (68.5%) at pH 7, contact time 90 min, adsorbent dose 0.1 g, and initial dye concentration 50 mg/L. The adsorption data followed the adsorption isotherm and Kinetics for both dyes. The removal of both dyes was a physical adsorption process, endothermic and spontaneous reaction. Column adsorption investigation was described by AB (Adams-Bohart) and YN (Yoon-Nelson) models. According to the economic view, the utilization of jarosite for dye removal is a cost-effective approach, because it is collected free of cost from industries. Henceforth, for the first time, toxic metal industry waste was successfully utilized as an adsorbent for wastewater treatment.

The present study evaluates the feasibility of using natural Lagerstroemia speciosa bark (NLSB) and chemically modified Lagerstroemia speciosa bark (CLSB) in removing Cr(VI) from aqueous solution in fixed bed column process. The effect of influent flow rate, bed depth and inlet Cr(VI) ion concentration on the Cr(VI) removal capacity of NLSB and CLSB was investigated. The column exhaustion time increased with increase in bed depth and reverse trend was obtained with increase in flow rate and influent Cr(VI) ion concentration. The Bohart-Adams, Thomas and Yoon-Nelson dynamic models were applied at various studied experimental conditions to predict the breakthrough curve behavior and to determine the characteristics fixed bed column parameters that are very crucial in scale up of the column process for its industrial scale application. Both Thomas and Yoon-Nelson models showed very good agreement with the column data and explained the mechanism of Cr(VI) adsorption by NLSB and CLSB in column process. The high Cr(VI) adsorption capacity and regeneration efficiency of NLSB and CLSB in column suggest its applicability in removal of Cr(VI) present in industrial effluents.

The adsorption behavior of basic, methylene blue (MB), and reactive, remazol brilliant violet 5R (RBV), dyes from aqueous solution onto Intsia bijuga sawdust-based activated carbon (IBSAC) was executed via batch and column studies. The produced activated carbon was characterized through Brunauer-Emmett-Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch studies were performed to investigate the effects of contact time, initial concentration, and solution pH. The equilibrium data for both MB and RBV adsorption better fits Langmuir model with maximum adsorption capacity of 434.78 and 212.77 mg/g, respectively. Kinetic studies for both MB and RBV dyes showed that the adsorption process followed a pseudo-second-order and intraparticle diffusion kinetic models. For column mode, the breakthrough curves were plotted by varying the flow rate, bed height, and initial concentration and the breakthrough data were best correlated with the Yoon-Nelson model compared to Thomas and Adams-Bohart model. The adsorption activity of IBSAC shows good stability even after four consecutive cycles.

In this work, equilibrium and dynamic adsorption tests of cadmium Cd (II) on activated carbons derived from different oxidation treatments (with either HNO₃, H₂O₂, or NaOCl, corresponding to GACoxN, GACoxP, and GACoxCl samples) are presented. The oxidation treatments determined an increase in the surface functional groups (mainly the acidic ones) and a decrease in the pHPZC (except for the GACoxCl sample). A slight alteration of the textural parameters was also observed, which was more significant for the GACoxCl sample, in terms of a decrease of both Brunauer-Emmett-Teller (BET) surface area and micropore volume. Adsorption isotherms were determined for all the adsorbents and a significant increase in the adsorption performances of the oxidized samples with respect to the parent material was observed. The performances ranking was GACoxCl > GACoxP > GACoxN > GAC, likely due to the chemical surface properties of the adsorbents. Dynamic tests in a fixed bed column were carried out in terms of breakthrough curves at constant Cd inlet concentration and flow rate. GACoxCl and GACoxN showed a significantly higher value of the breakpoint time, likely due to the higher adsorption capacity. Finally, the dynamic tests were analyzed in light of a kinetic model. In the adopted experimental conditions, the results showed that mass transfer is controlled by internal pore diffusion, in which surface diffusion plays a major role.

This study evaluates the feasibility of commercial chitosan (CQ) and modified chitosan (MQ) by epichlorohydrin to be used as a solid phase to remove fluorescein (FSC) from aqueous solutions by two different approaches: in batch and on a fixed column bed. For the batch study, all parameters that influence sorption capacity were evaluated, such as: pH, mass, ionic strength, temperature and time of contact. In the optimized condition, 75% removal was obtained for FSC using CQ, while the modification allowed an increase up to 99%, as well as an increase in the stability of the polymer. In the fixed column bed study, the influence of all the parameters was evaluated through breakthrough curves, and the thermodynamics parameters of each approach were obtained. The results of these studies demonstrate that the modification with epichlorohydrin enhanced the sorptive properties (from 35% to 95% in fixed bed experiments) and the polymer stability (making it insoluble), making it suitable to be used in wastewater treatment.