Liquid-solid Adsorption Research Articles

Application of the Southwell Plot method to determine equilibrium time in phosphate adsorption

Among the different factors that influence the liquid-solid adsorption technique, equilibrium time is one of the most relevant and requires a large number of experiments over a long period of time for its determination. This work evaluates the Southwell Plot as a further tool that can contribute to determining the equilibrium time in adsorption processes. It can also optimize the operating conditions in a batch system for the removal of phosphate in adsorbents produced from domestic sewage sludge and clam shell residue. Sewage sludge and clam shell residues were ground, sieved and sintered at 700 °C for 1 h. The material was characterized by thermal analyses (TG/DTG), chemical analysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and adsorption studies. The kinetic studies were investigated by varying the initial concentration of the phosphate solution and mass of the adsorbent. The equilibrium time was determined by applying the Southwell Plot method to the kinetic data and the results showed some fluctuations as a function of the adsorbent mass. At 0.30 g of the adsorbent in 30 mL of the phosphate solution, regardless of the initial phosphate concentration, the equilibrium time determined by the Southwell Plot was 4 h. The maximum phosphate adsorption capacity in this condition, determined by the Langmuir equation, was 49.45 mg g−1.

Perspective on the Future Approaches to Predict Retention in Liquid Chromatography.

The demand for rapid column screening, computer-assisted method development and method transfer, and unambiguous compound identification by LC/MS analyses has pushed analysts to adopt experimental protocols and software for the accurate prediction of the retention time in liquid chromatography (LC). This Perspective discusses the classical approaches used to predict retention times in LC over the last three decades and proposes future requirements to increase their accuracy. First, inverse methods for retention prediction are essentially applied during screening and gradient method optimization: a minimum number of experiments or design of experiments (DoE) is run to train and calibrate a model (either purely statistical or based on the principles and fundamentals of liquid chromatography) by a mere fitting process. They do not require the accurate knowledge of the true column hold-up volume V0, system dwell volume Vdwell (in gradient elution), and the retention behavior (k versus the content of strong solvent φ, temperature T, pH, and ionic strength I) of the analytes. Their relative accuracy is often excellent below a few percent. Statistical methods are expected to be the most attractive to handle very complex retention behavior such as in mixed-mode chromatography (MMC). Fundamentally correct retention models accounting for the simultaneous impact of φ, I, pH, and T in MMC are needed for method development based on chromatography principles. Second, direct methods for retention prediction are ideally suited for accurate method transfer from one column/system configuration to another: these quality by design (QbD) methods are based on the fundamentals and principles of solid-liquid adsorption and gradient chromatography. No model calibration is necessary; however, they require universal conventions for the accurate determination of true retention factors (for 1 < k < 30) as a function of the experimental variables (φ, T, pH, and I) and of the true column/system parameters (V0, Vdwell, dispersion volume, σ, and relaxation volume, τ, of the programmed gradient profile at the column inlet and gradient distortion at the column outlet). Finally, when the molecular structure of the analytes is either known or assumed, retention prediction has essentially been made on the basis of statistical approaches such as the linear solvation energy relationships (LSERs) and the quantitative structure retention relationships (QSRRs): their ability to accurately predict the retention remains limited within 10-30%. They have been combined with molecular similarity approaches (where the retention model is calibrated with compounds having structures similar to that of the targeted analytes) and artificial intelligence algorithms to further improve their accuracy below 10%. In this Perspective, it is proposed to adopt a more rigorous and fundamental approach by considering the very details of the solid-liquid adsorption process: Monte Carlo (MC) or molecular dynamics (MD) simulations are promising tools to explain and interpret retention data that are too complex to be described by either empirical or statistical retention models.

A new SeDeM-SLA expert system for screening of solid carriers for the preparation of solidified liquids: A case of citronella oil

Plating of liquids on the solid carrier to convert them into free-flowing powders is a lucrative technique as the solid carriers manifest high surface area, high adsorption capacities, stabilization properties and hence, ease the handling. Thus, selection of a well-qualified carrier as an adsorbent is of utmost importance. This article demonstrates a new SeDeM-SLA (Solid-Liquid Adsorption) expert system for screening of carriers. The original SeDeM tool is modified with two new parameters- Loss on drying is replaced by % oil released and Cohesion Index is replaced by adsorption capacity. The calculated value from the SeDeM-SLA diagram is termed as Index of Good Flow (IGF). In the present case study, citronella oil adsorbates were optimized based on the flow properties, % oil loading and release of the oil. The proposed model was successfully developed and results obtained could be well correlated to mechanism of oil adsorption and carrier properties.

Rare Earths (La, Y, and Nd) Adsorption Behaviour towards Mineral Clays and Organoclays: Monoionic and Trionic Solutions

Metals from electric and electronic waste equipment (WEEE) can be recovered by dissolution with acids followed by liquid–liquid extraction. A possible alternative to liquid–liquid extraction is liquid–solid adsorption, where sorbents efficiency is the key factor for process efficiency. In this respect, aim of this paper is the study of the behaviour of two solid sorbents for the recovery of Rare Earths (REs)—in particular, La, Nd, and Y—from scraps of end-of-Life (EOL) electronic equipment. Two solid matrices were considered: a pristine montmorillonite clay and a modified-montmorillonite clay intercalated with a commercial pentaethylen-hexamine. The capture ability of the solids was tested towards single-ion La, Nd, and Y solutions and a multi-element solution containing the three ions. Before and after the uptake step, samples of both the solid and liquid phases were analysed. For both sorbents, at lower metal initial concentrations, the ions were captured in similar amount. At higher concentrations, pure clay showed a high total uptake towards La ions, likely due to surface interactions with clay sites. The organoclay preferentially interacts with Nd and Y. Considering the presence of the polyamine, this behaviour was related to ion coordination with the amino groups. The capture behaviour of the two sorbents was related to the different physicochemical properties of the ions, as well as to the ionic radius.

Liquid–Solid Mass Transfer in Adsorption Systems—An Overlooked Resistance?

In liquid-solid adsorption, fluid film diffusion is typically faster than intraparticle diffusion, especially for microporous adsorbents. However, fluid film diffusion might play a significant role in the overall rate of the process for mesoporous-macroporous and non-porous solids. In most adsorption modeling studies, the fluid film diffusion step is typically ignored, which is not always justified. This article critically discusses the theory behind the liquid-solid mass-transfer coefficient in stirred vessels and presents the dissolution and adsorption methods adopted for estimating its value. Then, starting from the definition of the Biot number, an original analysis is developed with reference to selected studies. Surface versus pore diffusion of the adsorbate in the adsorbent is taken into account, and external versus internal mass-transfer resistance is considered to put the fluid film resistance back in the picture when needed. Iso-Biot charts where the operating points can be visualized are presented as well.

Batch and packed bed techniques for adsorptive aqueous phase removal of selected phenoxyacetic acid herbicide using sugar industry waste ash

Abstract Batch and packed bed adsorption of 4-chloro-2-methylphenoxyacetic acid (MCPA) herbicide was performed using bagasse fly ash (BFA) as an adsorbent. In batch process, characteristics of adsorbent, and the influence of adsorbent dosage, initial herbicide concentration, time, pH, particle size of adsorbent and temperature on adsorption were studied. Results disclose higher removal of MCPA on bigger particles of BFA owing to higher specific surface area because of greater carbon and lesser silica percentage in bigger particles. Application of isotherm models in present study indicates the best fitting of Langmuir and Temkin isotherms whereas the kinetic models suggest the suitability of pseudo second order and Elovich models. Thermodynamic study specifies the temperature preferred adsorption process. In packed bed technique, the effect of influent concentration, flow rate and bed height were investigated. The deactivation kinetic model which was previously considered only for studies in gas-solid adsorption is applied in this study to solid-liquid adsorption along with conventional packed bed models. In packed bed study, Bohart-Adams and Wolborska models are appropriate to explain the experimental data upto 60% saturation of the column. The deactivation kinetic model is found the best to elucidate the nature of breakthrough curves till the complete saturation of column. Batch capacity and packed bed capacity per m2 specific surface area of BFA is found about two and three times greater than the previously used adsorbents for MCPA respectively.

Thermodynamic interpretation of the drift and noise of gradient baselines in reversed-phase liquid chromatography using mobile phase additives

The drift and noise of acetonitrile-water gradient baselines (5-95%, v/v, 5 min linear gradient) in reversed phase liquid chromatography (RPLC) are recorded at a wavelength of 215 nm using 0.1% trifluoroacetic acid (TFA) as the mobile phase additive, a 4.6 mm × 150 mm 5 μm Symmetry-C18 RPLC column, and an Arc system (low-pressure gradient proportioning valve or GPV, pump with a stroke volume of either 66 or 132 μL, no mixer) as the LC instrument. These observations are predicted from solid-liquid adsorption thermodynamics which requires the measurement of the excess adsorption isotherm of acetonitrile from water onto the RPLC column and of the variation of the Henry’s constant of TFA as a function of the volume fraction of acetonitrile in the bulk mobile phase. The incomplete mixing of the acetonitrile and water packets delivered by the low-pressure GPV is represented by a sinusoidal perturbation of the programmed volume fraction of acetonitrile during the entire gradient. The variation of the TFA absorbance at 215 nm with increasing acetonitrile concentration is measured in order to transform TFA concentration into the observable absorbance unit. The drift and noise of the gradient baseline are calculated by solving numerically (Rouchon method) the equilibrium-dispersive (ED) mass balance equations of acetonitrile and TFA.The agreement between the calculated and observed gradient baselines is very good as the proposed model of chromatography accurately accounts for the displacement of TFA between stationary and mobile phases (early excess and late deficit of TFA concentration relative to 0.1%) and for the frequency (equal to the ratio of the applied flow rate to the stroke volume) and the amplitude of the periodic noise recorded during the gradient. From a practical viewpoint, the drift of the gradient baseline can be minimized by maximizing the ratio of the gradient volume to the hold-up volume ( > 10) and/or by minimizing the retention factor of the mobile phase additive in the water-rich eluent (k < 0.2). The reduction of the noise amplitude below 0.1 mAU as requested by the pharmaceutical industry imposes the ratio of the flow rate to the stroke volume of the pump to be larger than 1 Hz. This opens avenues towards the development of new GPV, pump, and mixers in order to mix efficiently the solvent packets delivered by conventional LC instrument.

CO 2 absorption of anhydrous colloidal suspension based silica nanospheres with different microstructures

Liquid absorption and solid adsorption technologies have been researched and reported widely for CO2 capture. Combining the advantages of these two capture materials, a novel anhydrous colloidal su...

CO2 absorption of anhydrous colloidal suspension based silica nanospheres with different microstructures

Liquid absorption and solid adsorption technologies have been researched and reported widely for CO2 capture. Combining the advantages of these two capture materials, a novel anhydrous colloidal suspension was synthesized by dispersing amine-modified microporous silica nanospheres in 2-[2-(dimethylamino) ethoxy] ethanol. In this study, solid, hollow, and porous silica nanospheres with different internal pore structures were synthesized and characterized. The effects of the silica nanosphere microstructures on diethylenetriamine loading and CO2 absorption in anhydrous colloidal suspensions were studied. Due to a more developed pore structure, the hollow and porous silica-based absorbents possessed stronger amine loading capacities compared to solid silicon-based absorbent, and the best absorption performance was an absorption capacity of 1.2543 mmol/g at a pressure of 150 kPa and a temperature of 300 K. The results indicated that pore structure had a significant influence on the absorption property, and the porous silica-based absorbent was more favorable for CO2 absorption than solid and hollow silica-based absorbents. Moreover, the pseudo-second-order model was successful in predicting the CO2 absorption process in colloidal suspensions.

High-Performance n -Hexane Purification by Nonporous Adaptive Crystals of Leaning Pillar[6]arene

The production of high-purity n-hexane under mild conditions is of great significance in both the petrochemical industry and synthetic chemistry. Here, we report an easy-to-operate and energy-effic...

A Method for Obtaining Liquid-Solid Adsorption Rates from Molecular Dynamics Simulations: Applied to Methanol on Pt(111) in H2O.

Adsorption is an important step in heterogeneous catalysis as it predetermines how many reactant molecules can participate in a surface reaction per unit time. While the rate of adsorption processes is well studied in gas-solid adsorption in both theory and experiment, such rates are still not well studied for liquid-solid adsorption. This is partly because the ever-changing configurations of liquid-phase solvent molecules impede the ability to study a molecule approaching a surface from a liquid phase by either experiment or theory. In this work, we develop a method using molecular dynamics (MD) simulations to study the rate of adsorption in liquid-solid adsorption processes. Specifically, we use MD to model the diffusion of a methanol molecule in aqueous solvent and its adsorption to a Pt(111) surface. We find that by approximating the solute motion as following the same displacement rates as a random walk model, the adsorbed and non-adsorbed states of the methanol molecule near the Pt(111) surface can be discerned and quantified. In particular, this methodology enables extracting a sticking coefficient and a macroscopically relatable adsorption rate. This method can be applied to arbitrary types of reactants and surfaces, as well as different liquid environments, thus providing a general tool for predicting quantitative adsorption rates of liquid-solid adsorption systems.

Facile preparation of void-buffered Si@TiO2/C microspheres for high-capacity lithium ion battery anodes

The well-constructed Si nanostructure anode is essential for achieving high performance lithium-ion battery. In this report, void-buffered Si@TiO2/C microspheres are fabricated via a facile solid-liquid adsorption template technology followed by calcination process. Here, for the first time, the green and low-cost TiCl4 solution is employed as the inorganic titanium precursor for synthesis of size-controllable TiO2 shell. The void buffer can be controlled by the annealing temperature and concentration of the precursor of template. The Si@TiO2/C combines the merits of controllable void for releasing the mechanical stress, robust TiO2/C shell for building stable SEI film, high electronic conductivity for improving charge transfer. This specific structure is demonstrated to be effective in alleviating the volume effect during cycling process. When Si@TiO2/C microspheres are evaluated as anode of lithium-ion battery, a high reversible specific capacity of 1384 mA h g−1 is obtained after 100 cycles at 200 mA g−1. Even at a high current density of 500 mA g−1, a reversible capacity of 1038 mA h g−1 can still be retained after 400 cycles. The high-capacity electrochemical performance and easy preparation methods demonstrate the Si@TiO2/C microspheres are considered as a very promising anode material for next-generation lithium-ion batteries.

Enhanced removal of ammonium from the aqueous solution using a high-gravity rotating packed bed loaded with clinoptilolite

A novel method for efficiently removing low levels of ammonium contamination from the aqueous solution using clinoptilolite in a high-gravity rotating packed bed (HGRPB) was developed. Our batch experiments have shown that irregular clinoptilolite gave better ammonium removal efficiencies due to higher specific surface area, and the adsorption data fitted better using pseudo-second-order adsorption kinetics than pseudo-first-order adsorption kinetics. HGRPB experiments have demonstrated that increasing rotating speeds will improve ammonium removal due to higher mass transfer of ammonium between the liquid and solid phases. The removal efficiency was 90% at the end of the fifth cycle (∼54 min) at a rotating speed of 1500 rpm using irregular clinoptilolite, with an initial ammonium concentration of 12.5 mg-N/L in distilled water and a flow rate of 180 mL/min. However, the removal efficiency was obviously lower in pond water than that in distilled water because of possible competitive adsorption of other cations in the pond water, suggesting modification of clinoptilolite to increase its selectivity for ammonium will be critical. This study has demonstrated the potential of using clinoptilolite in the HGRPB system to remove low levels of ammonium contamination in water and warrants the research need of HGRPB for biphasic liquid–solid adsorption processes.

Ion Exchange Modeling of the Competitive Adsorption of Cu(II) and Pb(II) Using Chemically Modified Solid Waste Coffee

The presence of potentially toxic metals such as Cu(II) and Pb(II) in aquifers and industrial effluents represents a serious health problem due to their high toxicity, non-biodegradability, and ability to bioaccumulate. In this study, the removal of these pollutants individually and as a binary mixture has been studied, using solid coffee waste modified with 0.6 M citric acid as the adsorbent, and a mathematical model based on the ion exchange mechanism was implemented to elucidate the adsorption equilibrium. The characterization of modified coffee waste showed a pH value at the point of zero charge of 2.97 and a high concentration of carboxylic groups, which are susceptible to ion exchange. Furthermore, the quantification of interchangeable ions confirmed that the main mechanism of adsorption is the ion exchange of metal ions with the protons present on the adsorbent’s surface. The experimental data of the individual and binary adsorption equilibrium using a model based on a phenomenological approach was analyzed. The phenomenological model was compared with the Freundlich and Langmuir empirical solid-liquid adsorption models. The results showed that the adsorption capacities of Cu(II) and Pb(II) individually were 1.46 and 1.18 meq/g, and in a binary mixture were 1.43 and 1.24 meq/g, respectively, at pH 5 and 30 °C. In addition, the separation coefficients from ion exchange model revealed the predominance of protons as an exchangeable ion, which is in accordance with the experimental evidence. Finally, the correlation coefficient showed that the proposed model predicts accurately the adsorption equilibrium.

Liquid-solid Adsorption of Cd(II) by Maghemite

Background: In this paper, the liquid-solid adsorption of Cadmium (II) is performed using magnetic nanoparticles that are based on maghemite nanoparticles (γ-Fe2O3), prepared by coprecipitation route. The adsorption procedure was carried out in batch mode and some parameters, such as time, initial metal concentration, initial pH solution, and weight of magnetic nanoparticles, were studied in order to assess the performance of maghemite in removing the ions Cd2+. Results: The adsorption equilibrium time was reached after shaking for 30 minutes. The maximum adsorption reached 100% at 10-3 mol.L-1 for 0.05g of magnetic nanoparticles. The results obtained showed that the initial pH value is an important parameter that affects the removal of Cd2+. Indeed, it was noted that the removal efficiency increases as the pH of the solution goes up. The kinetic and equilibrium studies were carried out, and the equilibrium data obtained were analyzed using the Langmuir and Freundlich isotherm models. The Langmuir isotherm showed a better fit for cadmium adsorption. The elution of Cd2+ was performed using 0.1 mol.L-1 sulfuric acid, and more than 90% of Cd2+ was desorbed after shaking for 90 minutes. Conclusion: The experimental capacity obtained was 52.63 mg g-1. Maghemite nanoparticles can be regenerated for uses, the cadmium can be concentrated in a small volume that facilitates waste discharge. In perspective, a study will be conducted on nanoparticles of maghemites to serve as a transport agent under the action of a magnetic field of drugs at the place to be treated. Keywords: Nanotechnologies, maghemite, liquid-solid adsorption, cadmium, adsorption isotherms, kinetic models.

Liquid–solid adsorption processes interpreted by fractal-like kinetic models

The transport of an adsorbate molecule from the bulk of a fluid phase to the active centre of an adsorbent particle involves complex mechanisms. Mechanisms need to be described by accurate mathematical expressions for the proper design of a fluid–solid adsorption unit. Here we investigate adsorption from the liquid phase with a focus on interrelationships among pollutants and adsorbents characteristics, dynamic adsorption results, and fractal-like modelling of experimental data from the literature. Among all models, the fractal pseudo-first-order’s model was the most statistically accurate. The value of the hybrid fractional error function ranged between 3 × 10−4 and 1 × 10−2. This value was in general one order of magnitude lower than that obtained for a canonical pseudo-first-order model, which overestimate the values of the degree of surface coverage by 10–20%. The fractal model involves the presence of an instantaneous rate coefficient, which ranged between orders 10−3 and 1 min−1. Adsorbents showing different features have been analysed, for example with variations in particle size (order 100 μm), specific surface area (order 102 m2 g−1), and total pore volume (order 10−1 cm3 g−1). For short adsorption times, the instantaneous rate coefficient was positively affected by (1) decrease in particle size; (2) increase in specific surface area and total pore volume; (3) increase in specific mesopore volume; (4) increase in average pore size. The heterogeneity parameter of the fractal model influences the time decay rate of the former coefficient. This parameter ranged between 0.138 and 0.478, and it was higher when: (1) the pore space is more crowded by already adsorbed molecules; (2) a larger degree of surface chemical heterogeneity is determined; (3) the mean micropore size is smaller; (4) the specific volume of ultramicropores is larger; (5) the pore size distribution is more polydispersed.

Spectroscopic and Thermodynamic Study of Biopolymer Adsorption Phenomena in Heterogeneous Solid-Liquid Systems.

Molecular selective adsorption processes at the solid surface of biopolymers in mixed solvent systems are poorly understood due to manifold interactions. However, the ability to achieve adsorptive fractionation of liquid mixtures is posited to relate to the role of specific solid–liquid interactions at the adsorbent interface. The hydration of solid biopolymers (amylose, amylopectin, cellulose) in binary aqueous systems is partly governed by the relative solvent binding affinities with the biopolymer surface sites, in accordance with the role of textural and surface chemical properties. While molecular models that account for the surface area and solvent effects provide reliable estimates of hydration energy and binding affinity parameters, spectroscopic and thermal methods offer a facile alternative experimental approach to account for detailed aspects of solvation phenomena at biopolymer interfaces that involve solid−liquid adsorption. In this report, thermal and spectroscopic methods were used to understand the interaction of starch- and cellulose-based materials in water–ethanol (W–E) binary mixtures. Batch adsorption studies in binary W–E mixtures reveal the selective solvent uptake properties by the biomaterials, in agreement with their solvent swelling in pure water or ethanol. The nature, stability of the bound water, and the thermodynamic properties of the biopolymers in variable hydration states were probed via differential scanning calorimetry and Raman spectroscopy. The trends in biopolymer–solvent interactions are corroborated by dye adsorption and scanning electron microscopy, indicating that biopolymer adsorption properties in W–E mixtures strongly depend on the surface area, pore structure, and accessibility of the polar surface groups of the biopolymer systems, in agreement with the solvent-selective uptake results reported herein.

Conventional and non-conventional adsorbents for wastewater treatment

The removal of contaminants from wastewaters is a major challenge in the field of water pollution. Among numerous techniques available for contaminant removal, adsorption using solid materials, named adsorbents, is a simple, useful and effective process. The adsorbent matter can be mineral, organic or biological. Activated carbon is the preferred, conventional material at the industrial scale. Activated carbon is extensively used not only for removing pollutants from wastewater streams, but also for adsorbing contaminants from drinking water sources, e.g., groundwater, rivers, lakes and reservoirs. However, the widespread use of activated carbon is restricted due to a high cost. In the last three decades, numerous approaches using non-conventional adsorbents have been studied for the development of cheaper and more effective adsorbents to eliminate pollutants at trace levels. This review gives an overview of liquid-solid adsorption processes using conventional and non-conventional adsorbents for pollutant removal. The manuscript outlines the principles of adsorption and proposes a classification for adsorbent materials. Finally, the various mechanisms involved in the adsorption phenomena are discussed.

Adsorption and anoxic degradation of typical pahs in bohai coastal sediments

This paper aims to disclose the adsorption and anoxic degradation processes of three typical polycyclic aromatic hydrocarbons (PAHs) in the coastal sediments of China’s Bohai Sea region. The PAHs are naphthalene (Nap), phenanthrene (Phe) and pyrene (Pyr). Several sediments samples were collected from Qinhuangdao Port, and subjected to adsorption and biodegradation experiments. Then, pseudo-first-order and pseudo-second-order kinetic models were tested to explain the kinetics of liquid-solid phase adsorption systems. It is discovered that the adsorption of the three PAHs on the coastal sediments matched pseudo- second-order kinetics, revealing that adsorption processes were essentially chemical reactions. In terms of equilibrium adsorption capacity, the three PAHs are ranked as Pyr>Phe>Nap. Next, Freundlich and Langmuir models were employed to fit the experimental data. The fitting results show that the adsorption of Nap, Phe and Pyr on the coastal sediments can be explained as mono-molecular layer adsorption. All the adsorptions of Nap, Phe and Pyr were exothermic reactions. In the anoxic sediments, 93.2% of Nap was removed after 30h, 96.6% of Phe was removed after 7d, and 98.1% of Pyr was removed after 42d. The detected metabolites of Nap were [4,4-dimethyl-2-cyclohexene-1-ol], [1-carboxyl,2-hydroxy, 4-methyl-cyclohexane], the metabolites of Phe were [3-ethoxy ethyl benzoate], [Phthalate (2-methyl propyl) ester] and the metabolites of Pyr were [2- methyl succinic acid, double (2-methyl propyl) ester], [Phthalate (2-methyl propyl) ester], [Phthalic acid butyl ester, 14 alkyl ester]. The findings shed new light on the research of PAHs adsorption and anoxic degradation in coastal sediments.

Removal of metronidazole from aqueous solution using activated carbon

Metronidazole antibiotic is a medication once discharged into the water after use, can react with living organisms and causing adverse effects to their lives. This kind of contaminant must be removed from wastewater and the technique adopted in this work is the liquid-solid adsorption method. The removal of metronidazole in aqueous solutions is carried out on powdered activated carbon. Different parameters such as solid/liquid ratio, temperature, pH, concentration, and contact time influencing this adsorption are examined. The Langmuir isotherm appears the most satisfactory is best suited for modeling the adsorption of metronidazole. In addition, the pH and the temperature do not seem to have any noticeable effect on the adsorption of metronidazole. The experimental results showed that metronidazole was removed at 64% for concentration of 50 mg/L for contact time of 20 min.