Nonlinear Adsorption Isotherm Research Articles

Efficient Simulation of Chromatographic Processes Using the Conservation Element/Solution Element Method

Chromatographic separation processes need efficient simulation methods, especially for nonlinear adsorption isotherms such as the Langmuir isotherms which imply the formation of concentration shocks. The focus of this paper is on the space–time conservation element/solution element (CE/SE) method. This is an explicit method for the solution of systems of partial differential equations. Numerical stability of this method is guaranteed when the Courant–Friedrichs–Lewy condition is satisfied. To investigate the accuracy and efficiency of this method, it is compared with the classical cell model, which corresponds to a first-order finite volume discretization using a method of lines approach (MOL). The evaluation is done for different models, including the ideal equilibrium model and a mass transfer model for different adsorption isotherms—including linear and nonlinear Langmuir isotherms—and for different chromatographic processes from single-column operation to more sophisticated simulated moving bed (SMB) processes for the separation of binary and ternary mixtures. The results clearly show that CE/SE outperforms MOL in terms of computational times for all considered cases, ranging from 11-fold for the case with linear isotherm to 350-fold for the most complicated case with ternary center-cut eight-zone SMB with Langmuir isotherms, and it could be successfully applied for the optimization and control studies of such processes.

Comparative analysis of linear and nonlinear equilibrium models for the removal of metronidazole by tea waste activated carbon.

Tea waste was carbonized at 400 °C for 45 min and modified with potassium hydroxide (KOH), to enhance the active sites for the adsorption of antibiotics. The developed tea waste activated carbon (TWAC) was used as a novel eco-friendly and cost-effective adsorbent for metronidazole (MZN) removal from aqueous solution. The textural and surface properties of the adsorbent were determined using Brunauer-Emmett-Teller (BET) and FT-Raman analysis. The BET surface was found to have increased from 24.670 to 349.585 after carbonization and KOH modification. The batch experimental parameters were optimized and equilibrium time was found to be 75 min. Linear and non-linear models were carried out on the adsorption isotherm and kinetics to determine the best fit for the adsorption data. The adsorption equilibrium data were well fitted by the Freundlich isotherm and pseudo-second order models, with higher regression correlation (R2) and smaller chi-square (χ2), as predicted by the non-linear model. The thermodynamic results revealed the adsorption of MZN as spontaneous, physical, and consistently exothermic in character. The activation energy value of 7.610 kJ/mol further revealed that the adsorption process is dominated majorly by physical adsorption. The removal of MZN onto TWAC was best described by the non-linear adsorption isotherm and kinetics model.

Platinum (IV) Recovery from Waste Solutions by Adsorption onto Dibenzo-30-crown-10 Ether Immobilized on Amberlite XAD7 Resin-Factorial Design Analysis.

Platinum is a precious metal with many applications, such as: catalytic converters, laboratory equipment, electrical contacts and electrodes, digital thermometers, dentistry, and jewellery. Due to its broad usage, it is essential to recover it from waste solutions resulted out of different technological processes in which it is used. Over the years, several recovery techniques were developed, adsorption being one of the simplest, effective and economical method used for platinum recovery. In the present paper a new adsorbent material (XAD7-DB30C10) for Pt (IV) recovery was used. Produced adsorbent material was characterized by X-ray dispersion (EDX), scanning electron microscopy (SEM) analysis, Fourier Transform Infrared Spectroscopy and Brunauer-Emmett-Teller (BET) surface area analysis. Adsorption isotherms, kinetic models, thermodynamic parameters and adsorption mechanism are presented in this paper. Experimental data were fitted using three non-linear adsorption isotherms: Langmuir, Freundlich and Sips, being better fitted by Sips adsorption isotherm. Obtained kinetic data were correlated well with the pseudo-second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. Thermodynamic parameters (ΔG°, ΔH°, ΔS°) showed that the adsorption process was endothermic and spontaneous. After adsorption, metallic platinum was recovered from the exhausted adsorbent material by thermal treatment. Adsorption process optimisation by design of experiments was also performed, using as input obtained experimental data, and taking into account that initial platinum concentration and contact time have a significant effect on the adsorption capacity. From the optimisation process, it has been found that the maximum adsorption capacity is obtained at the maximum variation domains of the factors. By optimizing the process, a maximum adsorption capacity of 15.03 mg g−1 was achieved at a contact time of 190 min, initial concentration of 141.06 mg L−1 and the temperature of 45 °C.

On-line optimization of four-zone simulated moving bed chromatography using an equilibrium-dispersion model: I. Simulation study

Simulated moving bed (SMB) chromatographic processes have been successfully applied to petrochemical, pharmaceutical, and fine chemical industries to separate the target products with high purity and yield since it was introduced in 1960s. Conventional four-zone SMB chromatography and its advanced variants are nowadays the most promising continuous processes for the separation of chiral active pharmaceutical ingredients (APIs). However, the design and optimization of SMB processes are still challenging issues due to their structural complexity and operational sensitivity. In this work, the equilibrium-dispersion model with nonlinear adsorption isotherms was applied for model based on-line optimization. The proposed optimization technique estimates the process states including the isotherm and kinetic parameters. The operating conditions are dynamically optimized ‘switch-by-switch’ in order to separate binary mixtures up to 99% product purity.

Synthesis of a novel polysuccinimide based resin for the ultrahigh removal of anionic azo dyes from aqueous solution

A novel hyper-cross-linked polyamide resin (PSI-PA) has been synthesized for the ultrahigh removal of Congo red (CR) and Eriochrom Black T (EBT) from aqueous solution. The mesoporous resin, having a specific surface area (98.80 m2 g−1), showed maximum adsorption capacity (Qmax) of 522.18 mg g−1 for CR (pH 9.0) and 460.34 mg g−1 for EBT (pH 6) at room temperature. The adsorption of these dyes was rapid and the equilibrium was attained within 4 h. The kinetic data was well-fitted by pseudo-second-order rate equation. Analysis of the surface chemical composition of loaded PSI-PA by XPS revealed the appearance of a new peak at around 166.0 eV (S 2p), confirming the adsorption of the sulfur-based dyes onto the resin. Examination of experimental data of dyes adsorption by a variety of non-linear adsorption isotherms and kinetic models suggested that the Langmuir model exhibited the best fit with high correlation coefficients for both CR (R2 = 0.9966) and EBT (R2 = 0.9934). PSI-PA has been extensively characterized by FT-IR, solid state 13C (CP-MAS) NMR, EDS, TGA and BET analysis. Moreover, PSI-PA exhibited 82% removal efficiency for dyes in simulated effluents, manifesting its promise and utility for treating industrial effluent.

Comparison of Linear and Nonlinear Kinetic Models and Adsorption Isotherms of Zinc from an Aqueous Solution by Biochar

Comparison of Linear and Nonlinear Kinetic Models and Adsorption Isotherms of Zinc from an Aqueous Solution by Biochar

MIL-53 (Fe) derived magnetic porous carbon as a robust adsorbent for the removal of phenolic compounds under the optimized conditions

The presence of phenolic compounds in aquatic environment, derived from industrial, domestic or agricultural processes adversely affects the human and animals. This study in aimed at the new and effectiveness of an adsorbent, magnetic porous carbon (MPC), for the removal of phenolic compounds including phenol and 4-nitrophenol from aquatic environment. MPC was synthesized from the metal-organic framework MIL-53 (Fe) via the direct pyrolysis at 600 °C. The MPC structure was characterized by several physical techniques and used for the adsorption experiments. To find the best conditions for the removal of phenol and 4-nitrophenol, we empirically investigated the effects of three variables (initial concentration, dosage and pH) on the removal efficiency using the response surface methodology (RSM). Under the RSM-based optimized conditions, up to 83% phenol was removed at the concentration of 16 mg/L, dosage of 0.7, and pH of 6.6, while the figure for 4-nitrophenol was 97%, at concentration of 26.0 mg/L, dosage of 0.75 g/L, and pH of 5.6. In addition, the nonlinear adsorption kinetics and isotherms were employed to interpret the mechanism and calculate the constants of adsorption rate. The uptake results suggested that the adsorption process was controlled by the chemisorption and the monolayer adsorption. The MPC exhibited the remarkable maximum adsorption capacities, which is 4 times (for phenol) and 5 times (for 4-nitrophenol) higher than those exhibited by origin MIL-53 (Fe). Plausible adsorption mechanisms were explained through dipole-dipole H-bonding, π–π interaction and electrostatic attraction. Because of high capacity, effortless performance and good reusability, the MIL-53 (Fe) derived porous carbon can be a promising material for phenolic species remediation in water.

Insights into nonlinear adsorption kinetics and isotherms of vanadium using magnetised coal-polyaniline

Insights into nonlinear adsorption kinetics and isotherms of vanadium using magnetised coal-polyaniline

A novel, initial guess free optimization algorithm for estimating parameters of batch kinetics model used to simulate adsorption of pollutant molecules in aqueous streams

Adsorption kinetics involved in the removal of phenol molecules polluting waterbodies was scrutinized using the popular and rigorous Homogeneous Surface Diffusion Model (HSDM). Adsorption of phenol depends on its molecular properties, characteristics of the adsorbent and operating conditions (Liu et al., 2010). These affect the dynamic and equilibrium parameters of the HSDM. Due to a boundary condition that involves an integral and a nonlinear adsorption isotherm, an analytical solution is not possible. The parameters of the HSDM, viz. the convective mass transfer coefficient in the fluid phase and diffusion coefficient in the solid phase are difficult to estimate from experimental kinetics data, through conventional optimization algorithms. These algorithms are sensitive to the quality of initial guesses and may frequently stall if the error function surface has a nearly flat topology. A novel, initial guess free and robust algorithm, termed as Elephant Herd Optimization algorithm (EHO), was developed in-house for reliably estimating the HSDM parameters. EHO is based on the social behavior of a herd of elephants and their instinct to navigate to water sources based on their strong memory. The proposed algorithm was considerably improved from the well-known particle swarm optimization technique (Kennedy and Eberhart, 1995). Conventional methods such as Nelder-Mead, genetic algorithm, and simulated annealing were compared against EHO for the attainment of global minimum and computational efficiency. EHO was successful in identifying the parameters with the smallest attainable error sum of squares based on experimental and predicted concentration values, lesser computational effort, lesser number of function evaluations and greater precision. EHO typically reduced the time required for parameter estimations by about 30% on an average with 40% lesser number of iterations when compared to the conventional methods. Also, the standard deviation in the estimated parameters upon repeated application of the EHO was about 52% lower than the conventional methods on an average. The implications of inaccurate predictions of the transport parameters from conventional algorithms on the adsorption kinetics are discussed.

Amberlite XAD7 resin functionalized with crown ether and Fe(III) used for arsenic removal from water

Abstract Water represents an essential resource for life and for all natural processes. Our existence and our economic activities are totally dependent on this precious resource. It is well known that into the developing countries the main resource of drinkable water is represented by underground waters, so their contamination with arsenic represents a real problem that needs to be solved. To solve the problem of arsenic water pollution, it was necessary to develop a series of chemical, physicochemical and biological methods to reduce arsenic concentrations from water. From all these methods, adsorption offers many advantages including simple and stable operation, easy handling of waste, absence of added reagents, compact facilities and generally lower operation cost. The goal of this paper is to study the sorption properties of a new adsorbent material prepared by impregnating Amberlite XAD7 resin with crown ether (dibenzo-18-crown-6 ether) and loaded with Fe(III) ions. Solvent impregnated resin (SIR) method was used for functionalization. Amberlite XAD7 resin functionalization was evidenced by energy dispersive X-ray analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis and determination of specific surface by the Brunauer, Emmett and Teller (BET) analysis. Equilibrium, kinetic and thermodynamic studies were performed in order to determine the removal efficiency of the studied adsorbent for arsenic removal from water. In order to study the As(V) adsorption mechanism the experimental data were modelled using pseudo-first-order and pseudo-second order kinetic models. Kinetic of adsorption process was better described by pseudo-second-order model. Experimental data were fitted with three non-linear adsorption isotherm models: Langmuir, Freundlich and Sips. Obtained experimental data were better fitted by Sips adsorption isotherm. The values of thermodynamic parameters (ΔG°, ΔH°, ΔS°) showed that the adsorption process was endothermic and spontaneous. The results proved that Amberlite XAD7 resin with crown ether and loaded with Fe(III) is an efficient adsorbent for the As(V) removal from water. The possibility of reuse the adsorbent material through adsorption and desorption cycles was also studied and it was found that the material can be used in five sorption-desorption cycles. Maximum adsorption capacity obtained experimentally being 18.8 μg As(V)/g material.

A simple and rapid approach to modeling chromium breakthrough in fixed bed adsorber

A simple mathematical model for predicting fixed bed adsorption dynamics is described. The model is characterized by a linear adsorption isotherm and a linear driving force expression for mass transfer. Its analytic solution can be approximated with an algebraic equation in closed form which is easily evaluated by spreadsheet computation. To demonstrate one application of the fixed bed model, a previously published adsorption system is used as a case study in this work. The adsorption system examined here describes chromium breakthrough in a fixed bed adsorber packed with imidazole functionalized adsorbent particles and is characterized by a nonlinear adsorption isotherm. However, the equilibrium behavior of the fixed bed adsorber is in essence governed by a linear adsorption isotherm due to the use of a low influent chromium concentration. It is shown that chromium breakthrough is predicted reasonably well by the fixed bed model. The model\'s parameters can be easily extracted from independent batch experiments. The proposed modeling approach is very simple and rapid, and only Excel is used for computation.

Theoretical Investigation of Thermal Effects in an Adiabatic Chromatographic Column Using a Lumped Kinetic Model Incorporating Heat Transfer Resistances

A nonequilibrium nonisothermal lumped kinetic model (LKM) is analytically and numerically investigated to evaluate the effects of inherent temperature fluctuations in an adiabatic chromatographic column. The model comprises convection–diffusion partial differential equations quantifying mass and energy balances in the mobile phase coupled with differential and algebraic equations for mass and energy in the stationary phase. Besides two mass transfer coefficients, two heat transfer coefficients are involved in the model equations. The properties of the considered model are investigated for linear concentration and temperature dependencies of the equilibrium loadings. The Laplace transformation and Eigen decomposition techniques are utilized to solve the set of equations. These solutions are helpful for understanding, analyzing, and interpreting the propagation speeds and shapes of both concentration and thermal fronts migrating in chromatographic columns. The moment generating property of the Laplace domain solutions is employed to obtain explicit analytical temporal moments of the concentration and energy profiles which provide instructive tools to analyze the properties of the model considered and to estimate unknown model parameters from measured transients. For illustration, several case studies are carried out by assuming realistic model parameters. The applicability range of the analytical solutions derived is assessed by comparing selected specific results with numerical results of a nonequilibrium and nonisothermal model by considering nonlinear adsorption isotherms.

Effective adsorptive removal of 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine by pseudographitic carbon: kinetics, equilibrium and thermodynamics

Environmental contextExplosive organic compounds such as 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are major constituents of ammunition materials. These compounds are of environmental concern because they can have a significant impact on ecosystems and humans. Through investigations of adsorption kinetics, isotherms and thermodynamics, we demonstrate the suitability of pseudographitic carbon for removing TNT and RDX from groundwater, and additionally confirm the viability of the use of pseudographitic carbon through comparison with other adsorbents. Abstract2,4,6-Trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) – common explosives in military munitions – can easily enter groundwater supplies and have an adverse impact on human health. There is great concern about the need to remove these explosives from groundwater, and this study presents pseudographitic carbon (PGC) prepared from edible sugar as a material to remove explosives from contaminated groundwater via adsorption. The purity and physicochemical characteristics of the PGC were characterised using advanced spectroscopic techniques. The adsorption mechanism and its efficiency were investigated in terms of the non-linear adsorption kinetics, isotherms and thermodynamics using TNT and RDX adsorption data. The results of the non-linear modelling indicate that TNT and RDX adsorption was determined by rate-limiting monolayer exothermic adsorption on the homogeneous PGC surface. Ionic strength was studied with various ions, and the results indicate that the adsorption of TNT and RDX was significantly influenced by divalent cations and the carbonate anion. The results of desorption and re-use tests indicate that acetone and acetonitrile are the best desorbing agents. The PGC can be recycled and re-used for up to 3 cycles, with insignificant loss in adsorption efficiency. Finally, the PGC was applied to real spiked groundwater to evaluate its applicability in the field in removing TNT and RDX. The overall results indicate that PGC is a cost-effective and efficient adsorbent that effectively removes the organic explosives from groundwater, thereby reducing risk to humans and the aqueous environment.

Modeling nitrogen leaching from Andosols amended with different composted manures using LEACHM

Andosols, distributed widely around the Pacific basin, have unique soil–water and solute transport properties because of their stepwise water retention curves and high anion-adsorption capacity. The model modification and verification for these properties are crucial for evaluating the potential for improved agricultural management (e.g., using organic matter instead of inorganic fertilizer) to reduce N loss from the soils. Here, we improved an existing biogeochemical model, LEACHM, to predict long-term N leaching from Andosols amended with composted manure, without optimization to fit measured field data. The modified model was verified by observations from a 5.6-year lysimeter experiment with different rates of inorganic N fertilizer plus composted manure (100 + 0, 75 + 25, or 25 + 75%) of two different types (cattle, swine) on lettuce, sorghum (as a catch crop), and Chinese cabbage in rotation. Incorporation of Durner’s bimodal model dramatically improved predictions of drainage water volume and evapotranspiration. The non-linear Langmuir adsorption isotherms for soil NH4 + and NO3 − improved model performance in simulating crop N uptake and N leaching loss. The RMSE, R2, and index of Agreement were evaluated as satisfactory in all lysimeters. Our model explained reasonably well that improved agricultural management decreased in current available N addition rates by 8.82–35.6% and reduced in the yearly averaged NO3 leaching by 8.70–41.8%. A modified model relating soil hydraulic properties and N adsorption properties could thus accurately predict N leaching under different long-term N application rates/types, and could be useful for supporting agricultural management decisions in cropped Andosols.

Pb (II) removal from water using surface-modified polythiophene-coated rice husk ash nanocomposite

ABSTRACTIn the present work, a novel nanocomposite adsorbent, polythiophene (PTh)/rice husk ash (RHA), has successfully been synthesized in the presence of hydroxypropyl cellulose (HPC) as the surfactant. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and thermal gravimetric analysis (TGA). The synthesized PTh/RHA/HPC nanocomposite adsorbent was applied as an efficient sorbent for lead ion [Pb (II)] removal from contaminated water. Concentration of Pb (II) ion before and after adsorption was measured using atomic absorption spectroscopy. Several variables affecting the extraction efficiency of the nanoadsorbent i.e., adsorbent dosage, metal ion concentration, extraction time, and adsorption conditions were investigated. The optimum pH value for Pb (II) ion adsorption on PTh/RHA/HPC nanocomposite was about four with maximum efficiency of about 96.58%. The highest efficiency of adsorption was 98.12% for sample with 0.05 g adsorbent in 50 mL of 10 mg/L Pb (II) solution. Equilibrium studies were also performed with known linear and non-linear adsorption isotherms including Langmuir, Freundlich, and Temkin from which the best result was achieved with Freundlich isotherm, with R2 = 0.995 representing multilayer adsorption on heterogeneous structure of the adsorbent. The pseudo-first-order model and the pseudo-second-order model were adopted to analyze the adsorption kinetics of Pb (II) on PTh/RHA/HPC. The consistency of the experimental qe (9.92 mg/g) with qe (10 mg/g) calculated from the pseudo-second-order kinetic model illustrated that the adsorption of Pb (II) onto PTh/RHA/HPC at initial concentration of 50 mg/L was probably controlled by chemical adsorption.

Combined Homogeneous Surface Diffusion Model – Design of experiments approach to optimize dye adsorption considering both equilibrium and kinetic aspects

Adsorption, a popular technique for removing azo dyes from aqueous streams, is influenced by several factors such as pH, initial dye concentration, temperature and adsorbent dosage. Any strategy that seeks to identify optimal conditions involving these factors, should take into account both kinetic and equilibrium aspects since they influence rate and extent of removal by adsorption. Hence rigorous kinetics and accurate equilibrium models are required. In this work, the experimental investigations pertaining to adsorption of acid orange 10 dye (AO10) on activated carbon were carried out using Central Composite Design (CCD) strategy. The significant factors that affected adsorption were identified to be solution temperature, solution pH, adsorbent dosage and initial solution concentration. Thermodynamic analysis showed the endothermic nature of the dye adsorption process. The kinetics of adsorption has been rigorously modeled using the Homogeneous Surface Diffusion Model (HSDM) after incorporating the non-linear Freundlich adsorption isotherm. Optimization was performed for kinetic parameters (color removal time and surface diffusion coefficient) as well as the equilibrium affected response viz. percentage removal. Finally, the optimum conditions predicted were experimentally validated.

A degenerate elliptic-parabolic system arising in competitive contaminant transport

The objective of this work is to study a coupled system of degenerate and nonlinear partial differential equations governing the transport of reactive solutes in groundwater. We show that this system admits a unique weak solution provided the nonlinear adsorption isotherm associated with the reaction process satisfies certain physically reasonable structural conditions, by addressing a more general problem. In addition, we conclude, that the solute concentrations stay non-negative if the source term is componentwise non-negative and investigate numerically the finite speed of propagation of compactly supported initial concentrations, in a two-component test case.

Experimental and CFD modeling of diazinon pesticide removal using fixed bed column with Cu-modified zeolite nanoparticle

In this study, perlite was employed as a low-cost source of Si and Al in the synthesis of sodalite zeolite by means of the hydrothermal synthesis method. The structural characterization of this zeolite was performed by XRD, SEM and FTIR analysis. Nanoparticles of Cu2O (30–60 nm) were loaded on the zeolite and utilized as an adsorbent to remove diazinon in fixed bed column. The SEM-EDX of modified zeolite indicates that the amount of copper loading on the zeolite was 4.5 wt.%. The potential parameters effects such as flow rate (0.5, 1 and 1.5 mL/min), initial concentration (50, 75 and 100 mg/L) and bed height (5–15 cm) were investigated on the column performance. A general model was used to predict the breakthrough curves of the fixed bed for diazinon sorption, given the external mass transfer resistance and the axial dispersion with non-linear adsorption isotherm. COMSOL software was employed for the numerical calculation of equations in the model. There was a good agreement between the predicted theoretical breakthrough curves and the experimental results.

Surface modified polythiophene nanocomposite using HPC and DBSNa for heavy metal ion removal.

In the present work, surface modified nanocomposite adsorbents polythiophene (PTh)/rice husk ash (RHA) have successfully been synthesized in the presence of hydroxyl propyl cellulose (HPC) and sodium dodecyl benzene sulfonate (DBSNa) as surfactants. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR), and the synthesized nanocomposite adsorbents were applied as an efficient sorbent for Pb(II) ion removal from contaminated water and the removal efficiency was compared to pure PTh/RHA composite. Several variables affecting the extraction efficiency of the nanoadsorbent i.e., adsorbent dosage, metal ion concentration, extraction time, and adsorption conditions were investigated. The highest efficiency of adsorption (98.12%) was achieved with 0.05 g of PTh/RHA/HPC nanocomposite adsorbent in 50 mL of 10 mg/L Pb(II) solution. Equilibrium studies were also performed with known linear and non-linear adsorption isotherms including Langmuir, Freundlich and Sips from which the best result was achieved with Freundlich and Sips isotherms representing multilayer adsorption on heterogeneous structure of the adsorbent. The pseudo-first-order model and the pseudo-second-order model were adopted to analyze the adsorption kinetics of Pb(II) on PTh/RHA/HPC and PTh/RHA/DBSNa. The consistency of the experimental adsorption capacity with the ones calculated from the pseudo-second-order kinetic model illustrated that the adsorption of Pb(II) onto both adsorbents at initial concentration of 50 mg/L was probably controlled by chemical adsorption.

Influence of the precursor chemical composition on heavy metal adsorption properties of hemp (Cannabis Sativa) fibers based biocarbon

Waste hemp (Cannabis sativa) fibers were used as sustainable and renewable raw materials for production of low-cost biocarbon sorbent for heavy metals removal. Carbon precursors of different chemical composition were obtained by oxidative and alkaline treatments of hemp fibers. Influence of lignocellulosic precursor chemical composition on hemp fibers-based biocarbon (HFB) characteristics was examined by BET surface area measurement, scanning electron microscopy and mass titration. It was found that lignin content and polymorphic transformation of cellulose increase the SBET of microporous HFBs, while hemicelluloses induce more homogeneous distribution of adsorption active sites. Heavy metal ions adsorption onto HFBs is primarily influenced by the amount of surface oxygen groups, while specific surface area plays a secondary role. Equilibrium data obtained for lead ions adsorption were analyzed by different nonlinear adsorption isotherms, and the best fitting model was chosen using standard deviation and Akaike information criterion (AICC). The maximum adsorption capacities of HFBs ranged from 103.1 to 116.3 mg Pb/g. Thermodynamic parameters showed that Pb2+ adsorption onto HFBs is a spontaneous and complex endothermic process, suggesting the coexistence of physisorption and chemisorption mechanisms.