Mass Transfer Steps Research Articles

A DFT-based kinetic equation for Co3O4 decomposition reaction in high-temperature thermochemical energy storage

Thermal energy storage supports stable grid integration of variable renewable energy sources by reducing power curtailment and generation costs. Thermochemical energy storage (TCES) offers high energy density and long-duration, long-distance storage advantages, making it a focus in large-scale applications such as concentrated solar power plants. Metal oxide systems like Co3O4/CoO are widely used due to their operational flexibility, yet limited understanding of their decomposition kinetics hinders optimization of TCES materials and reactor design. In this study, we developed a rate equation based on density functional theory and transition state theory to identify the reaction mechanisms and rate constants at the gas–solid interface, prior to predict Co3O4 decomposition kinetics. A microkinetic model was then constructed to couple surface reactions with oxygen ion diffusion across the bulk, which was integrated into a reactor model accounting for mass transfer steps. The model’s accuracy was validated against the data from the micro-fluidized bed thermogravimetric analyzer experiments. For particles smaller than 150 μm, the formation step of adsorbed O2 (energy barrier of 0.8 eV) controls the reaction rate, while gas diffusion dominates the reaction rate for particles larger than 500 μm. To conclude, the optimal conditions for maximizing charge–discharge kinetics in TCES applications were identified as: 850–900 °C, 0–10 vol% O2, and 150–500 μm. This model provides theoretical guidance for optimizing TCES materials and reactor design, reducing experimental costs while maintaining accuracy.

The influence of amino anchoring position on SnO2/biochar for electroreduction of CO2 to HCOOH

Biochar derived from biomass resources as a carrier to load SnO2 for electroreduction of CO2 not only can benefit carbon emissions, but it also can achieve waste utilization. However, the weak CO2 mass transfer and conductivity ability of SnO2/biochar limits its applications to such eCO2RR processes. This study focused on modifying SnO2/biochar with amino groups and investigated the effects of positioning of amino groups on the catalyst’s physicochemical properties and electrocatalytic behaviors. Elemental analysis revealed that anchoring amino groups on biochar (SnO2/C-NHx) is advantageous for increasing amounts of amino groups attached, thereby enhancing biochar adsorption energy and subsequently increasing the loading of Sn. The CO2 adsorption curve indicated that amino groups anchored on biochar facilitate CO2 adsorption due to high specific surface area of biochar. X-ray photoelectron spectroscopy showed that amino groups anchored on SnO2 (NHx-SnO2/C) resulted in highly electron-rich centers on Sn, which promoted electron transfer between the catalyst and CO2. Electrochemical tests demonstrated the improved performance of amino-modified SnO2/biochar. SnO2/C-NHx exhibited enhanced Faraday efficiency, whereas NHx-SnO2/C showed higher current density. The disparity in electrochemical performance can be mainly attributed to the different selectivity towards rate-controlling steps of electron transfer and mass transfer induced by the various positions of amino groups anchoring.

Analysis, identification, and application of distribution of relaxation times in CMP slurry

This study delves into the mechanistic roles of oxidants, complexing agents, and inhibitors in slurries through of Distribution of Relaxation Times (DRT) analysis. The influence of varying concentrations of these chemicals on electrochemical processes is discussed. This article divides the spectrum obtained through DRT analysis into four different frequency regions and differentiate naming through electrode reaction process: the double-layer charging step, the charge transfer step, the mass transfer step, and the surface transformation step by adsorption or chemical alterations at the electrode surface. The results reveal that the peak observed in the low-frequency range at 10−2–10° Hz is associated with mass transfer step, while the relaxation peak at 10°–102 Hz corresponds to the charge transfer process, while the relaxation peak occurring at 102–104 Hz is linked to the surface transformation step, and the first peak emerging in the 104–106 Hz range is attributed to double-layer charging step.

Analysis of heat transfer coefficient and skid marks in a slab reheating furnace considering beam misalignment and contact heat conduction

Accurate analysis of slab heat transfer characteristics is crucial for optimal control of reheating furnaces. This paper established a half furnace model to describe the heat and mass transfer and slab step heating processes in a walking beam reheating furnace. The contact heat conduction and beams misalignment are fully considered. The distribution of total heat transfer coefficient and the effect of stepping strategies on skid mark severity are investigated. The results show that the contact thermal resistance accounts for 1/8 of the conductivity thermal resistance of skid buttons and welding pads and has a lighter effect on the skid marks. The misalignment of the water-cooled beams effectively eliminated the original skid marks and minimized the range of the new ones, but the new skid mark severity before discharge from the furnace remains at 121 °C. The total heat transfer coefficient showed a wave distribution on the slab bottom surface and varied in the range of about −0.72 to 1.71 due to the beam shielding. On the slab top surface, it followed a stepped distribution. Stepping while advancing in soaking zone effectively improve the new skid mark temperature and reduce the skid mark severity by 24 °C. Increasing the stepping number can also reduce the influence of skid marks on the temperature of slab end, thus improving the temperature uniformity of the slab head and tail.

Experimental investigation and modeling of the impact of random packings on mass transfer in fluidized beds

This study investigates the impact of two novel settings of bubbling fluidized beds equipped with random metal packings on the mass transfer. To do this, a comprehensive approach is applied that integrates experiments and modeling and explores the relevance of the different underlying mechanisms involved in interphase mass transfer in fluidized beds. Firstly, the mass transfer of water from moisturized silica gel particles to dry air is studied in both a packed-fluidized bed and a freely bubbling bed with no packing. The experimental set-up consists of a cylindrical bubbling fluidized-bed column with an inner diameter of 22 cm. Silica-gel particles with a mean particle diameter of 797 μm are used as bed material. The total bed amount ranges from 4 to 8 kg, while the fluidization number (F) varies between 1.7 and 2.3. Two types of packing, RMSR (stainless steel thread saddle rings) and Hiflow (stainless steel pall rings) are examined and compared to the reference case of a bubbling bed with no packing. The height of the packed section is maintained at 60 cm. The results show that, at all operating conditions, the use of packings enhances the amount of desorbed water in the fluidized bed. The increase is up to 17%, as compared to the bed without packing. The effect is believed to be inhibition of bubble growth in the packed-fluidized bed. To study this further, a mass-transfer model is introduced to analyze the different mass-transfer steps (intra-particle, particle surface to emulsion gas, and emulsion gas to bubble gas) in packed-fluidized beds compared to beds with no packing. TGA experiments are applied to describe the intra-particle mass transfer through a desorption kinetic model. Model analysis shows that the main resistance for mass transfer occurs across the bubble-emulsion boundary. The calculated value of the mass transfer coefficient for this, Kb, at reference conditions (6 kg of silica gel and F = 2.3) is 7.6e-5 s−1 with packings (in average) and 6.2e-5 s−1 without packings, i.e. a 23% improvement in the governing mass-transfer coefficient.

Modeling of tritium release behavior of biphasic Li2TiO3–Li4SiO4 ceramics

Biphasic Li2TiO3–Li4SiO4 ceramics have been proposed as advanced tritium breeder for solid-type breeding blankets of fusion reactors. However, the mechanism of tritium release from biphasic Li2TiO3–Li4SiO4 ceramics remains to be elucidated. In this study, an integrated numerical model for tritium release from biphasic Li2TiO3–Li4SiO4 ceramics was constructed for the first time. In the proposed model, besides the mass transfer steps for tritium release from single-phase ceramics (e.g. Li2TiO3 and Li4SiO4), a mass transfer step between the interfacial layers of Li2TiO3 and Li4SiO4 was also included to take into account the effect of two-phase interface in Li2TiO3–Li4SiO4 ceramics. By using this model, numerical simulations of tritium release from Li2TiO3–Li4SiO4 ceramics with different phase ratio and grain size were performed. The simulation results showed that the mass transfer of tritium atoms between the interfacial layers of Li2TiO3 and Li4SiO4 can effectively enhance tritium release from Li4SiO4 in biphasic Li2TiO3–Li4SiO4 ceramics. Furthermore, increasing phase ratio of Li2TiO3 and decreasing grain size of Li2TiO3 were both beneficial to tritium release from biphasic Li2TiO3–Li4SiO4 ceramics at lower temperature. The modeling work consolidated the presumption that the two-phase interface could play an important role in the tritium release process of biphasic Li2TiO3–Li4SiO4 ceramics.

Influence of Al contents on the long-term corrosion behaviors of cold-sprayed Zn-xAl coatings

ZnAl coating is considered one of the most economic candidates for marine static immersive corrosion protecting technology, in which the Al/Zn ratio is quite crucial to achieve a certain aggressive ions concentration corrosion. In this study, different Al contents Zn-xAl composite coatings were prepared using low-pressure dynamic cold spraying, potentiodynamic polarization and electrochemical impedance spectroscopy techniques were implied to reveal the long-term corrosion behaviors in 3.5 wt% NaCl solution and experimentally optimize the Al and Zn composition of the composite coating for marine static immersion corrosive resistance. The results showed that the weight loss kinetics curve of Zn-xAl composite coatings conforms well to a linear equation over time after logarithms, an increase in Al content leads to enhanced corrosion resistance of Zn-xAl composite coatings. After 1440 h immersion, the optimum Zn95Al composite coating, with high ECorr (−1.522 V) and low ICorr ((4.881 ± 0.98) × 10−5 A/cm2), presented the best corrosion resistance, due to the compact network passive film composing of Al(OH)3 and Al2(OH)5Cl∙2H2O, which slowed down mass-transfer step of Zn/Al elements.

Control-Oriented Reduced-Order Modeling of Conversion Efficiency in Dual-Layer Washcoat Catalysts With Accumulation and Oxidation Functions

Abstract This work proposes a model for predicting conversion efficiency in multifunctional catalysts with dual-layer washcoat. The mass transfer is more relevant in these devices than in single-layer washcoats due to additional transport steps between the catalytic layers. In addition, the different reaction mechanisms between layers make the concentration of the chemical species differ in each layer. To deal with this boundary while considering the need for real-time computation, a reduced-order explicit solver for the convective diffusive reactive transport is presented for the case of dual-layer washcoats. Assuming one-dimensional quasi-steady flow, the solution procedure consisted of substituting the diffusive interfacial fluxes in the bulk gas and washcoat conservation equations by expressions that depend explicitly on the average concentration in the gas phase. The solution was then applied to model the performance of dual-layer oxidation catalysts with reductant accumulation in one washcoat layer, such as diesel oxidation catalyst (DOC) and ammonia slip catalyst (ASC) systems, during driving cycles. First, the response of these catalysts was analyzed by comparing them against experimental data and considering additional parameters provided by the model. Next, the importance of the mass transfer limitations was discussed to complete the analysis. The proposed model was compared with a simplified solver where the mass transfer steps were omitted, thus deteriorating the prediction capabilities in some driving cycle phases. Finally, a sensitivity study was performed to assess the impact of the mesh size on the prediction capabilities and computational requirements.

Fe3O4-chitosan nanocomposite as a magnetic biosorbent for removal of nickel and cobalt heavy metals from polluted water

Recently, natural polymers like chitosan have gained attention as promising adsorbents for water treatment. By combining chitosan with magnetic nanoparticles, their adsorption capabilities can be enhanced. In this study, chitosan-magnetite nanocomposite (CMNC) was synthesized via coprecipitation method to remove nickel and cobalt from aqueous solutions. The physicochemical properties of the synthesized CMNC were investigated by various techniques, including FESEM, TEM, XPS, FTIR, XRD, and VSM. The electron microscopy results confirmed the uniform dispersion of magnetite nanoparticles within CMNC nanocomposites, while VSM confirmed their significant magnetic properties. The adsorption experiments showed that at optimal conditions (pH = 6, contact time = 2 h, adsorbent dosage = 2 g/l), CMNC has high adsorption capacities of 30.03 mg/g for Ni2+ and 53.19 mg/g for Co2+. Furthermore, the adsorption data fitted best with the Langmuir isotherm, show that the active sites on CMNC are energetically homogenous. According to kinetic analysis, the experimental data were in good agreement with both pseudo-second-order and intra-particle diffusion models, which suggest that chemical sorption, along with mass transfer steps, influence the overall adsorption process. Finally, investigating the thermodynamic parameters (∆Gads, ∆Hads, ∆Sads) showed that the adsorption process on CMNC was endothermic and spontaneous, with stronger interactions observed between CMNC and Co2+ compared to Ni2+.

Mass transfer mechanism and model of CO2 absorption into a promising DEEA-HMDA solvent in a packed column

Mass transfer performance plays an important role in solvent evaluation as well as design and scale-up of CO2 absorption process. The mass transfer process of CO2 absorption into blended DEEA -HMDA solution was studied over different operating conditions in a lab-scale absorption column packed with Sulzer DX structured packing. The effect of those operating parameters on KGav was fully investigated and discussed in this work. Meanwhile, mass transfer mechanism of CO2 absorption into blended DEEA-HMDA solution was comprehensively presented by identifying the rate-controlling step of mass transfer and the reaction zone of CO2 with amines, which could provide the operation guideline for running plans. In addition, a new KGav model was proposed and developed on basis of the observed experimental value of KGav, which gave a much better predication performance in comparison with empirical Kohl-Risenfield-Astarita model and Sheng model with respect to AAD.

Analysis of Reaction Kinetics of the Ozonation of Phenolic Compounds and Assessment of the Role of Mass Transfer in the Overall Rate

The ozonation technique for biorefractory phenolic wastewater is preferred as a clean technology. However, its effectiveness and successful implementation on the commercial scale is crucial. The understanding of the rate-determining step and reliable reaction kinetics is the essence to the design and scale-up of ozonation reactors. In the case of phenolic wastewater, it is found that both mass transfer and chemical reaction contribute to the overall reaction rates. However, the mass transfer resistance is often significant in studies that determine the ozonation rate constant. This has resulted in discrepancies in the reported values of the intrinsic reaction kinetic parameters, and such apparent rate constants cannot be useful for suitable reactor design. The aim of this work is to analyze past works on the reaction kinetics of the ozonation of phenol, chlorophenols, and nitrophenols and determine the role of mass transfer steps in the overall reaction rate. The value of the volumetric liquid-side mass transfer coefficient (kLa) is estimated from the overall observed rates using the theory of mass transfer with chemical reaction, and these are found to be appropriate for the reactor geometry used in the respective works. In this way, our appraisal of the literature has provided key insights, which are yet unfamiliar, and renders useful the large body of data published in the literature, which otherwise remains unutilized.

Purification of Biodiesel via Nanofluid using Liquid-Liquid Extraction in a Membrane Contactor

Recently, attention has been paid to nanofluids due to their contribution to enhancing heat and mass transfer in different industrial applications. Consequently, a nanofluid composed of SiO2 nanoparticles (NPs) and distilled water as base fluid was adopted as a solvent to promote the removal of impurities, methanol, and glycerol, from crude biodiesel using liquid-liquid extraction in the membrane contactor. The presence of NPs significantly enhanced the methanol and glycerol removal efficiency. The optimum concentration of NPs in nanofluid was 0.01 wt%. It was found that adding 0.01 wt% of NPs to the distilled water increased the methanol removal efficiency from 76.4% to 93.1% upon using crude biodiesel with methanol and glycerol content of 2000 ppm and 1 wt%, respectively, at a constant flow rate of solvent and biodiesel of 200 mL min⎼1. Meanwhile, the glycerol removal efficiency increased from 76.2% to 94.5%. The results revealed that the solvent flow rate was the controlling mass transfer step.

Debromination of Waste Circuit Boards by Reaction in Solid and Liquid Phases: Phenomenological Behavior and Kinetics

The debromination of waste circuit boards (WCBs) used in computer motherboards and components has been studied with two different pieces of equipment. Firstly, the reaction of small particles (around one millimeter in diameter) and larger pieces obtained from WCBs was carried out with several solutions of K2CO3 in small non-stirred batch reactors at 200-225 °C. The kinetics of this heterogeneous reaction has been studied considering both the mass transfer and chemical reaction steps, concluding that the chemical step is much slower than diffusion. Additionally, similar WCBs were debrominated using a planetary ball mill and solid reactants, namely calcined CaO, marble sludge, and calcined marble sludge. A kinetic model has been applied to this reaction, finding that an exponential model is able to explain the results quite satisfactorily. The activity of the marble sludge is about 13% of that of pure CaO and is increased to 29% when slightly calcinating its calcite at only 800 °C for 2 h.

Develop and validate a mathematical model to estimate the removal of indoor VOCs by carbon filters

Adsorption-based air filters, especially carbon-based ones, are usually employed to remove VOCs from indoor air. Conducting tests at ppm level, which is substantially higher than the actual indoor concentration of VOCs, is recommended for reducing the test duration. Consequently, developing a model for estimating the service life of adsorptive filters under actual conditions is imperative.A comprehensive model that considers axially dispersed plug flow for interpellet mass transfer and pore surface diffusion model (PSDM) with variable surface diffusivity for intrapellet mass transfer was used to predict the performance of two filters exposed to three VOCs. First, the results of experiments conducted at concentrations ranging from 9 to 90 ppm in a bench-scale setup were used to compute the Dubinin-Radushkevich (D-R) isotherm parameters, which are concentration-independent. Then, the surface diffusivities at zero loading for various adsorbate-adsorbent systems were determined by fitting the developed model into the results of the experimental data performed at concentrations of 9 ppm or 30 ppm. Finally, the model was validated using experimental data which were conducted at lower concentrations, a higher velocity and on a full-scale setup.The inter-model comparison was carried out by comparing the comprehensive model with four other models to study the importance of various mass transfer steps. Finally, in sensitivity analysis, five dimensionless parameters (Pe, St, Edp, Eds and Dg) were examined to investigate their impact on the filter's efficiency.

Rethinking of the intraparticle diffusion adsorption kinetics model: Interpretation, solving methods and applications

Adsorption is a widely used unit process in various fields, such as chemical, environmental and pharmaceutical, etc. The intraparticle diffusion adsorption kinetics model is one of the most widely used adsorption kinetics models. However, the application and solving method of this model have yet to be discussed. This model has two forms (qt = kt1/2 and qt = kt1/2 + constant, where qt is the adsorption capacity at time t, k and constant are the model parameters), which have not been unified yet. Moreover, the interpretation of this kinetics model lacks a theoretical basis (if the line passes through the origin point (0, 0), the adsorption is dominated by the intraparticle diffusion; if not, it is a multiple adsorption process). In this study, we analyzed the proper equations of the intraparticle diffusion model and their applications, discussed the interpretation of the mass transfer steps revealed by this model, and provided the solving methods. The result indicated that the piecewise function qt = k1t1/2 (0 ≤ t ≤ t1); qt - qt = t1 = k2(t – t1)1/2 (t1 < t ≤ t2) is the proper form of this model. The adsorbate diffusion in the pores inside the adsorbent is the mass transfer step revealed by this model. The statistical parameters should be used to evaluate the fitting results instead of judging whether the model lines pass through the origin point (0, 0). We provide the solving methods to use the Origin and Microsoft EXCEL software to solve the model. Our study established the method for application of the intraparticle diffusion model.

In situ and Operando Spectroscopies in Photocatalysis: Powerful Techniques for a Better Understanding of the Performance and the Reaction Mechanism.

In photocatalysis, a set of elemental steps are involved together at different timescales to govern the overall efficiency of the process. These steps are divided as follow: (1) photon absorption and excitation (in femtoseconds), (2) charge separation (femto- to picoseconds), (3) charge carrier diffusion/transport (nano- to microseconds), and (4 and 5) reactant activation/conversion and mass transfer (micro- to milliseconds). The identification and quantification of these steps, using the appropriate tool/technique, can provide the guidelines to emphasize the most influential key parameter that improve the overall efficiency and to develop the "photocatalyst by design" concept. In this review, the identification/quantification of reactant activation/conversion and mass transfer (steps 4 and 5) is discussed in details using the in situ/operando techniques, especially the infrared (IR), Raman, and X-ray absorption spectroscopy (XAS). The use of these techniques in photocatalysis was highlighted by the most recent and conclusive case studies which allow a better characterization of the active site and reveal the reaction pathways in order to establish a structure-performance relationship. In each case study, the reaction conditions and the reactor design for photocatalysis (pressure, temperature, concentration, etc.) were thoroughly discussed. In the last part, some examples in the use of time-resolved techniques (time-resolved FTIR, photoluminescence, and transient absorption) are also presented as an author's guideline to study the elemental steps in photocatalysis at shorter timescale (ps, ns, and µs).

Multifilm Mass Transfer and Time Constants for Mass Transfer in Food Digestion: Application to Gut-on-Chip Models

This review highlights the involvement of mass transfer in animal food-digestion processes. There may be several mass-transfer steps during the dissolution of food components, starting from the food itself, moving into the digestive juices, then moving through the walls of the gastrointestinal tract. These steps create a sequence of film resistances to mass transfer, where one film resistance often limits the overall mass-transfer process. Mass-transfer rates, mass-transfer coefficients, and the time scales and time constants for different parts of the food-digestion process are all interlinked, and the connections have been explained. In some parts of the food-digestion process, the time constants for the mass-transfer process are similar to the residence times for food digestion, emphasising the importance of mass transfer in these parts of food digestion, such as the duodenum. The mass-transfer and transport behaviour for in vivo human digestive systems and in vitro guts-on-a-chip may be very similar, suggesting that cells on the intestine walls, whether in vitro (guts-on-a-chip) or in vivo, may see similar transport behaviour for both nutrients towards the cells, and waste products away from them.

57‐4: Invited Paper: Progress on Key Innovations in Direct‐View μLED Display Manufacturing

Applied Materials reported earlier on an innovative approach to μLED‐based front plane technology using a single wavelength GaN LED emitter with Cd‐free quantum dots for color conversion. This proprietary μLED front plane technology incorporates several key innovations such as the use of high external quantum efficiency dice in ultraviolet wavelength spectrum (vs. red/green/blue), highest photon extraction efficiency at small die‐size, fewer number of mass transfer steps with high yield, and a four‐subpixel backplane architecture to allow for a simple, cost‐effective repair strategy. A picture of this display is shown below.

Removal of indoor air ozone using carbon-based filters: Systematic development and validation of a predictive model

Exposure to ozone can cause several adverse health effects on human beings. Carbon-based filters are usually used for the removal of ozone from indoor air. The main problem with Carbon-based filters technology is the exhaustion of carbon because of irreversible reactions with ozone. Therefore, the knowledge of the service life of filters is crucial for building engineers and designers. Since testing at low indoor concentrations is time-consuming and expensive, the existing standards suggest experimenting with high concentrations. Thus, predictive models need to be developed to estimate the service life of filters. This work provides a model to estimate the breakthrough curves of three different combined (multi-layer) filters. The model augmented mass transfer equations with a reaction rate model and divided them into interpellet mass transfer and kinetic models. First, the reaction rate parameters were measured by fitting the model onto experimental data of all filters challenged with 9 ppm or 90 ppm of ozone. This was followed by validating the model for lower concentrations. In addition, to show the model validity for real-life application, its prediction was compared with the experimental data collected using the full-scale experimental setup and higher velocity. There was excellent agreement between the model prediction and the experimental results for all filters. Furthermore, an inter-model comparison was performed to determine the importance of different mass transfer steps. The results showed internal diffusion and axial dispersion as rate-limiting steps along with reaction. Finally, a sensitivity analysis was conducted on reaction kinetic parameters, axial dispersion coefficient, external mass transfer coefficient, and activated carbon particle porosity, which indicated negligible effects of external mass transfer and porosity variations.

Humic acid and nano-zeolite NaX as low cost and eco-friendly adsorbents for removal of Pb (II) and Cd (II) from water: characterization, kinetics, isotherms and thermodynamic studies

Humic acid as a green-sorbent was synthesized from marine sediments. While kaolin was modified to nano-zeolite NaX. Different tools such as FT-IR, SEM, EDX and XRD were applied to confirm the characteristics of the generated green-sorbents. Different factors such as pH, contact time, sorbent dosage, initial metal ion concentration, temperature and interfering ions were carefully examined and used to optimize the batch adsorption process for Cd2+ and Pb2+. A small dose of nano-zeolite of 100 mg was required to attain the maximum adsorption of Pb2+ at pH about 7, shacking time at 60 min and Pb2+ concentration at 30 ppm. Also, the maximum sorption capacity of Cd2+ ions on nano-zeolite was achieved in a neutral medium and very short contact time implying the economic feasibility of the adsorption process. In the case of humic acid, the maximum removal capacity for Pb2+ and Cd2+ was operated at acidic medium and shacking time was 40 min. Metal ions remediation results were evaluated by some adsorption isotherm models at different temperatures. The kinetic and thermodynamic variables were also computed. The data fitted very well with the linear Langmuir and the pseudo-second-order model implying a favourable adsorption process. The sorption of Cd2+ and Pb2+ was regulated by both external mass transfer and intraparticle diffusion steps over the whole range of concentrations, as shown by the results. The metal ions removal percentage from four real water samples by green sorbents were applied and provides good evidence of two sorbents as promising eco-sorbent for removal of heavy metal ions.