Sorbent Particle Size Research Articles

Equilibrium studies and kinetics mechanism for the removal of basic and reactive dyes in both single and binary systems using EDTA modified rice husk.

The potential of using ethylenediamine tetraacetic acid modified rice husk (ERH) to remove different types of dyes, namely basic and reactive dyes were studied. Sorption characteristic of ERH showed that it was pH dependent. The kinetics of sorption for both dyes was rapid within the first 60 min regardless of its initial concentration. Using the pseudo-second order kinetics model, the predicted uptakes of Methylene Blue (MB) and Reactive Orange 16 (RO16) agreed closely with experimental values obtained. Three isotherm models were used to fit with equilibrium data, namely Langmuir, Freundlich and BET models. It was found that the equilibrium fitted well in Freundlich isotherm with higher regression coefficient value, R2. Thermodynamic parameters showed that the sorption of process of MB and RO16 are exothermic and endothermic, respectively. Decrease in sorbent particle size led to an increase in the sorption of dyes. The study revealed that ERH is suitable to use as a single sorbent to remove both MB and RO16 in all systems. Key words: EDTA modified rice husk, adsorption, binary mixture system, methylene blue, reactive orange 16.

Adsorption of Crude Oil Using Meshed Groundnut Husk

There is an increasing awareness of the impact of spilled crude oil and its refined products on human health and environment. The potential of using groundnut husk, agro-based waste, which is not only ubiquitous but indiscriminately littered around Nigerian urban areas, as an adsorbent in removal of oil spilled on water was investigated. Groundnut shell, a waste generated in local vegetable oil processing plants, has been converted into a low cost adsorbent. The groundnut husk was treated and meshed to adsorb crude oil from water at various experimental conditions. Investigations include the effects of sorbent dosage, particle size, contact time and temperature on the adsorption of crude oil. Meshed groundnut shell, especially less than 150 µm, exhibited high affinity for oil adsorption with time. The optimum adsorption temperature range lies between 25 – 45°C. The adsorption data indicates that a pseudo-second-order equation could be used to study the adsorption kinetics and the correlation coefficient of 0.9985 indicates that the sorption process is dominated by adsorption process. The results demonstrate that crude oil removal by adsorption onto this abundantly available low cost and readily biodegradable material is feasible. With high affinity for oil and low water pick up, meshed groundnut shell adsorbent could be said to be oleophilic or hydrophobic.

Effectiveness of acid-treated agricultural stones used in biopurification systems to avoid pesticide contamination of water resources caused by direct losses: Part I. Equilibrium experiments and kinetics

Several recent publications report the use of low-cost and locally available adsorbents in biopurification systems to eliminate pesticides from water. Nonetheless, the literature is insufficient to cover this problem, and more investigations are needed in this field to evaluate the possible application of economical adsorbents to prevent pesticide water resources contamination caused by direct losses. This study focuses on the fate of endosulfan metabolites, in small-scale biopurification systems, using as adsorbents treated and untreated organic agricultural stones (date, olive and avocado). The effects of sorbent particle size, adsorbent dose, contact time, concentration of pesticide solution and temperature on the adsorption processes were systematically studied in batch experiments. Pesticide determination was carried out using stir bar sorptive extraction and gas chromatography coupled with mass spectroscopy. Maximum removal efficiency (94.8%) was reached for endosulfan sulfate (0.1 mg L −1) using the acid-treated date stones (ATOS) fraction <125 μm (solid/liquid ratio: 1 g L −1). According to the general behavior of the adsorption mechanism, date stones show the higher removal efficiency followed by olive and avocado stones, respectively. The analyses of the results reveal that the thermo chemical treatment improves notably the pesticides adsorption efficiency of the studied sorbents and that the adsorption decreases when the pesticide solubility rises. Experimental adsorption data were analyzed according to various kinetic models. Lagergren and Morris–Weber equations were applied to fit the kinetic results. The second order model was the most suitable and intra-particle diffusion was found to be the rate controlling the adsorption process.

Carbonaceous Composites from Agricultural Wastes for Adsorption of Hydrocarbon Contamination in Water

&lt;p&gt;Mechanical recovery of oil by oil sorbents is one of the most important countermeasures in marine oil-spill response. The preparation of oil-sorbents from agricultural waste increases economic return and reduces pollution. The sorption capacities of the carbonized rice husks and the apricot stone compared in relation to different petroleum products. Sorption capacity showed strong dependence on the particle size of sorbent and oil film thickness. The phase composition, microstructure and morphology of the composite material C/SiO&lt;sub&gt;2&lt;/sub&gt;, prepared by carbonize of rice husks were investigated by X-ray diffraction analysis, FTIR spectrometry and scanning election microscope&lt;em&gt; &lt;/em&gt;(SEM).&lt;/p&gt;

Kinetics of Adsorption at Solid/Solution Interfaces Controlled by Intraparticle Diffusion: A Theoretical Analysis

The utility of Weber−Morris and Lagergren linear representations for describing the kinetics of sorption at solid/solution interfaces controlled by intraparticle diffusion is discussed. The effects of different sorbent particle sizes and nonlinear adsorption isotherm equations (including the nonlinearity caused by surface energetic heterogeneity) and the changing sorbate concentration in the bulk phase have been taken into account. The conclusion can be drawn that both Lagergren and Weber−Morris plots seem to be general linear representations inherent in the intraparticle diffusion model and can be used for most adsorption systems. However, for quantitative analysis of kinetic data, more sophisticated methods need to be applied. Moreover, reliable conclusions can be drawn about a given system only by combined analysis of kinetic and equilibrium data.

FBC desulfurization process using coal with low sulfur content, high oxidizing conditions and metamorphic limestones

A metamorphic limestone and a dolomite were employed as SO2 sorbents in the desulfurization of gas from coal combustion. The tests were performed in a fluidized bed reactor on a bench and pilot scale. Several parameters such as bed temperature, sorbent type, and sorbent particle size at different Ca/S molar ratios were analyzed. These parameters were evaluated for the combustion of coal with low-sulfur/high-ash content, experimental conditions of high air excess and high O2 level in fluidization air. Under these conditions, typical of furnaces, few published data can be found. In this work, a medium level of desulfurization efficiency (~60%) for Ca/S = 2 was obtained.

Adsorptive features of acid-treated olive stones for drin pesticides: Equilibrium, kinetic and thermodynamic modeling studies

The adsorption behavior of drin pesticides from aqueous solution onto acid treated olive stones (ATOS) was investigated using stir bar sorptive extraction and gas chromatography coupled with mass spectroscopy. The effects of sorbent particle size, adsorbent dose, contact time, concentration of pesticide solution and temperature on the adsorption processes were systematically studied in batch shaking sorption experiments. Maximum removal efficiency (94.8%) was reached for aldrin (0.5 mg L −1) using the fraction 63–100 μm of ATOS (solid/liquid ratio: 1 g L −1). Experimental data were modeled by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms. The Freundlich isotherm model ( R 2 = 0.98–0.99) fitted the equilibrium data better than the Langmuir and D–R isotherm models, with low sum of error values (SE = 1.4–9.2%). The mean adsorption free energy derived from the D–R isotherm model ( R 2 = 0.95–0.99) showed that the adsorption of drin pesticides was taken place by weak physical forces, such as van der Waals forces and hydrogen bonding. The calculated thermodynamic parameters, Δ H, Δ S and Δ G prove that drin pesticides adsorption on ATOS was feasible, spontaneous and exothermic under examined conditions. The pseudo first order, pseudo second order kinetic and the intra-particle diffusion models were used to describe the kinetic data and rate constants were evaluated.

Drin pesticides removal from aqueous solutions using acid-treated date stones

This work describes the potential applicability of chemically and thermally treated date stones for removing drin pesticides (aldrin, dieldrin and endrin) from aqueous solutions. The effect of several parameters, such as sorbent particle size, adsorbent dose, shaking speed, shaking time, concentration of pesticide solution and temperature, was evaluated by batch experiments. Pesticide determination was carried out using stir bar sorptive extraction and gas chromatography coupled with mass spectroscopy. Maximum removal efficiency (93%) was reached using 0.1 g of acid-treated date stones (ATDS) (63–100 μm) and 100 mL of aldrin (0.5 mg L −1). The removal efficiency of drin pesticides decreased in the order of aldrin, dieldrin and endrin, and decreased as the temperature rose. Adsorption data were processed according to various kinetic models. Lagergren and Morris-Weber equations were applied to fit the kinetic results. The second order model was the most suitable on the whole, and intra-particle diffusion was found to be the rate-controlling the adsorption process. According to adsorption kinetic data, 3.5 h were considered as the equilibrium time for determining adsorption isotherms. Adsorption data were analyzed by the Langmuir, Freundlich and Dubinin–Radushkevich adsorption approaches. Experimental results showed that the Freundlich isotherm model best described the adsorption process. In addition, thermodynamic parameters such as Δ H, Δ S and Δ G were calculated. Negative values of Δ H and Δ G indicate the exothermic and spontaneous nature of pesticide adsorption on ATDS.

Sorption of Nitrobenzene from Aqueous Solution on Organoclays in Batch and Fixed-Bed Systems

Organoclays were synthesized using different quaternary ammonium salts namely, stearyldimethylbenzylammonium chloride, dioctadecyldimethylammonium chloride, and hexadecyltrimethylammonium bromide and employed as a sorbent for sorption of nitrobenzene from aqueous solution. Among the organoclays studied, stearyldimethylbenzylammonium as organic modifier was found to have highest sorption capacity and was further used in fixed-bed sorption study. The effect of flow rate, sorbent particle size, feed concentration, temperature, and the amount of organic modifier in organoclay on sorption of nitrobenzene were studied. The column parameters required for the design of the fixed-bed sorption systems such as time for primary sorption zone to move up its length, total time required for establishment of primary sorption zone, rate at which the exchange zone is moving up/down through the bed, fractional capacity, the height of the exchange zone, percentage of the total column saturated at breakthrough and breakthrough capacity were evaluated on the basis of breakthrough curves. Desorption of nitrobenzene was also carried out by water as elution solvent. The Yoon−Nelson model was used to depict the breakthrough behavior for sorption of nitrobenzene on organoclay in the fixed-bed system.

KINETIC AND EQUILIBRIUM STUDIES OF CR(III) AND CR(VI) SORPTION FROM AQUEOUS SOLUTION USING ROSA GRUSS AN TEPLITZ (RED ROSE) WASTE BIOMASS

The biosorption of Cr(III) and Cr(VI) from synthetic solution using dried untreated and pretreated Rosa gruss an teplitz waste biomass was evaluated in this study. The results showed that initial pH, biosorbent dose, sorbent particle size, initial metal concentration, time and temperature affected chromium uptake capacity of rose biomass. The effect of twenty different pretreatments including gaseous and other reagents on Cr(III) and Cr(VI) uptake capacity of Rosa gruss an teplitz waste biomass was comprehensively described. Uptake capacity of Rosa gruss an teplitz waste biomass was significantly affected after pretreatment. The metal uptake capacity of biomass was not only found related to nature of pretreatment but also found strongly related to oxidation state of chromium. The estimation of the correlation coefficients for Cr(VI) showed that the experimental data fit better to Freundlich model. The Langmuir isotherm provided the best correlation for Cr(III) onto the rose waste biomass. The biosorption phenomenon was dependent on the temperature with maximum adsorption at 30˚C. Biosorption of Cr(III) and Cr(VI) ions on to biomass followed pseudo 2nd order adsorption kinetic model. The results confirmed that rose waste biomass is a potential biomaterial to remove Cr(III) and Cr(VI) ions with a high biosorption capacity 45.03 mg/g and 48.75 mg/g for Cr(III) and Cr(VI) respectively.

Kinetics of sorption of lead on bed sediments of River Hindon, India

A number of low cost waste sorbent have been used for removal of heavy metals, however, few studies have been carried out on the sorption process on riverbed sediments in their natural state of occurrence. Stream sediments adsorb certain solutes from streams, thereby significantly changing the solute composition, but little is known about quantitatively describing sorption phenomena and rates of these processes. In the present investigation, sorption of lead ions on river bed sediments of river Hindon, a tributary of river Yamuna, India has been studied to demonstrate the role of bed sediments in controlling metal pollution. The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time and particle size has been studied. The sorption of lead ions increased with respect to pH and sorbent dose and decreased with sorbent particle size. Two important geochemical phases, iron and manganese oxide, also play important role in the sorption process. The sorption data were analysed using Langmuir and Freundlich isotherm models to determine the mechanistic parameters related to the sorption process. Further, although lead ions have more affinity for the fine fraction of the sediment, but the overall contribution of coarser fraction to sorption is more as compared to clay and silt fraction. The kinetic data suggest that the sorption of lead on bed sediments is an endothermic process, which is spontaneous at low temperature. The uptake of lead is controlled by both bulk and intraparticle diffusion mechanism.

Bismuth recovery from acidic solutions using Cyphos IL-101 immobilized in a composite biopolymer matrix

Impregnated resins prepared by the immobilization of an ionic liquid (IL, Cyphos IL-101, tetradecyl(trihexyl)phosphonium chloride) into a composite biopolymer matrix (made of gelatin and alginate) have been tested for recovery of Bi(III) from acidic solutions. The concentration of HCl slightly influenced Bi(III) sorption capacity. Bismuth(III) sorption capacity increased with IL content in the resin but non-linearly. Maximum sorption capacity reached 110–130 mg Bi g −1 in 1 M HCl solutions. The mechanism involved in Bi recovery was probably an ion exchange mechanism, though it was not possible to establish the stoichiometric exchange ratio between BiCl 4 − and IL. Sorption kinetics were investigated through the evaluation of a series of parameters: metal concentration, sorbent dosage, type and size of sorbent particles and agitation speed. In order to reinforce the stability of the resin particles, the IL-encapsulated gels were dried; this may cause a reduction in the porosity of the resin particle and then diffusion limitations. The intraparticle diffusion coefficients were evaluated using the Crank's equation. Additionally, the pseudo-first-order and pseudo-second-order equations were systematically tested on sorption kinetics. Metal can be desorbed from loaded resins using either citric acid or KI/HCl solutions. The sorbent could be recycled for at least three sorption/desorption cycles.

CYPHOS IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride) Immobilized in Biopolymer Capsules for Hg(II) Recovery from HCl Solutions

A composite polymer (made of gelatin and alginate) was used for the synthesis of Cyphos IL 101-immobilized resins. These resins (with varying size and different ionic liquid (IL) content) have been tested for the recovery of mercury from concentrated HCl solutions (0.1–5 M HCl concentrations). Prior to the study of sorption performance on resins, the reactivity of Cyphos IL 101 versus mercury was tested using solvent extraction methodology. These results showed that the extraction was hardly affected by the concentration of HCl and that an ion exchange mechanism was probably involved in metal recovery (binding of HgCl4 2-). The performance of these resins for Hg(II) recovery was tested through sorption isotherms and uptake kinetics, investigating the effect of resin size, ionic liquid content, metal concentration, agitation speed, and resin state (dry state versus wet state). Sorption capacity (which was proportional to the IL content) can reached up to 150 mg Hg g−1 in 1 M HCl; this sorption capacity was decreased by increasing chloride concentration. The kinetics were described well by the pseudo-second order equation and by the intraparticle diffusion equation (the so-called Crank's equation). The intraparticle diffusion coefficient was in the range of 10−11–1.2 × 10−10 m2 min−1. The kinetic profiles were controlled by the IL content, sorbent dosage, and the sorbent particle size. Drying of the resins significantly decreased diffusion rates in the resins. The presence of competitor metals did not affect sorption capacity except when stable chloro-anionic species such as in the case of Zn(II) were formed. Mercury can be desorbed using 6 M nitric acid solutions; and the sorbent can be recycled for at least six sorption/desorption cycles without significant decrease in the sorption performance.

Mercury vapor release from broken compact fluorescent lamps and in situ capture by new nanomaterial sorbents.

The projected increase in the use of compact fluorescent lamps (CFLs) motivates the development of methods to manage consumer exposure to mercury and its environmental release at the end of lamp life. This work characterizes the time-resolved release of mercury vapor from broken CFLs and from underlying substrates after removal of glass fragments to simulate cleanup. In new lamps, mercury vapor is released gradually in amounts that reach 1.3 mg or 30% of the total lamp inventory after four days. Similar time profiles but smaller amounts are released from spent lamps or from underlying substrates. Nanoscale formulations of S, Se, Cu, Ni, Zn, Ag, and WS2 are evaluated for capture of Hg vapor under these conditions and compared to conventional microscale formulations. Adsorption capacities range over 7 orders of magnitude, from 0.005 (Zn micropowder) to 188 000 μg/g (unstabilized nano-Se), depending on sorbent chemistry and particle size. Nanosynthesis offers clear advantages for most sorbent chemistries. Unstabilized nano-selenium in two forms (dry powder and impregnated cloth) was successfully used in a proof-of-principle test for the in situ, real-time suppression of Hg vapor escape following CFL fracture.

Comparison of the mopping ability of chemically modified and unmodified biological wastes on crude oil and its lower fractions

Activated and unactivated powders of goat hair and coir (coconut husk) separated into two particle sizes were used to mop up spills of crude oil, diesel, kerosene and petrol. It was observed that the materials (sorbents) mopped up appreciable volumes of the hydrocarbon liquids (sorbates) within 90min of contact. Activation, particle size of sorbents and molecular weight (chain length) of sorbates (hydrocarbon) are major determining factors. Carbonization and particle size enhanced the mopping ability as follows – carbonized 325μm>uncarbonized 325μm>carbonized 625μm>uncarbonized 625μm, thus activated sorbents with large surface area (small particle size) mopped more hydrocarbons than unactivated of the same particle size. The sorbates were mopped in the order – crude oil>diesel>kerosene>petrol. It was further observed that goat hair (keratin protein) with oleophilic and aquaphobic properties adsorbed more of all the hydrocarbons than coir at all sizes and treatment. Large quantities of the mopped oils were recovered by mere pressing while the waste sorbents with 0.5–2.0% leachable residual oil could be utilized as alternative to fire wood.

Decarbonation Rates of Cycled CaO Absorbents

Decarbonation rates of cycled CaO sorbent were measured for a wide range of particle sizes (0.25−4 μm), temperatures (747−830 °C), and relative CO2 concentrations (0−95%). The decarbonation rate was found to decay exponentially with an increase in partial CO2 pressure that can be explained by assuming CaO nuclei formation is the rate-limiting step. A differential particle model using two variable parameters was successfully applied to fit the experimental data. An approximate analytical expression is put forward for the decarbonation rate as a function of sorbent texture, temperature, CO2 pressure, particle size, and Sherwood number.

Removal of total phenols from olive-mill wastewater using an agricultural by-product, olive pomace

The purpose of this study was to investigate the sorption of total phenols, which are contained in olive-mill wastewater (OMWW), on solid by-products of olive pomace processing mills. Preliminary batch experiments were conducted using three different types of olive pomace, dried olive pomace (OP-1), dried and solvent extracted olive pomace (OP-2) and dried, solvent extracted and incompletely combusted olive pomace (OP-3). According to the results, OP-3 showed high performance for total phenols sorption and stability. For sorbent concentration of 10 g L −1 and sorbate concentration of 50 mg L −1, more than 40% of initial total phenols concentration was removed. Sorption kinetics was well described by the pseudo-second order rate model ( R 2 > 0.99). Total phenols removal efficiency was improved by increasing sorbent concentration and solution's pH or decreasing particle size of the sorbent material. The Langmuir and Freundlich isotherms sufficiently described OP-3 sorption capacity for the concentration range studied (50–500 mg L −1). Fixed bed sorption experiments showed that lower flow rates and smaller particle size of sorbent resulted in longer column exhaustion time and higher initial removal efficiency. Experiments with thermally or chemically regenerated OP-3 showed that sorption capacity deteriorated after regeneration.

Removal of Hydrogen Sulfide from a Steam-Hydrogasifier Product Gas by Zinc Oxide Sorbent

Removal of H2S by a commercially available zinc oxide sorbent was studied using a packed-bed reactor for desulfurizing the gas produced from steam-hydrogasification of carbonaceous materials. Experimental runs were conducted to monitor sulfur removal efficiency and H2S breakthrough time for the operation variables such as reaction temperature, steam content, space velocity, inlet H2S concentration, and sorbent particle size. For the inlet gas with 45 vol % steam content, the initial sulfur removal efficiency exhibited a maximum around 636 K. Varying the steam content of inlet gas affected the equilibrium of sorbent sulfidation in a reversible way, leading to the decrease of sulfur capture capacity of the sorbent as the steam content increased. Increasing the space velocity from 8 000 to 24000 h-1 decreased sulfur capture capacity significantly, indicating the deterioration of gas−solid contact in the reactor at the increased gas flow rates. Inlet H2S concentration was varied from 100 to 800 ppmv to reflec...

Mercury Sorption on Chitosan

Mercury sorption on chitosan was investigated in batch and continuous systems. Chitosan sorption properties were determined through sorption isotherms. Langmuir and Freundlich equations were used for the modeling of isotherms at pH 5. In batch systems, maximum sorption capacities reached 550 mg Hg/g. Sorption kinetics have been studied as a function of sorbent particle size and stirring rate. Dynamic removal of mercury was tested in a fixed bed reactor investigating the following parameters: particle size, column size, flow velocity and metal ion concentration. Clark and Adams-Bohart models were evaluated for the simulation of breakthrough curves. This study shows that chitosan is an effective sorbent for the treatment and recovery of mercury from dilute effluents at near neutral pH.

Increasing the efficiency of an air separation plant by varying the cycle stage durations

A mathematical model of a plant for oxygen-enriched air production by pressure swing adsorption is proposed. The model takes into account the experimentally determined actual dependence of the longitudinal dispersion coefficient on the gas velocity and the sorbent particle size. The relationship between the plant efficiency and the duration of each of the operating cycle stages is studied using an ad hoc computer program for numerically solving the model equations. It is shown that optimization of the durations of cycle stages increases the thermodynamic efficiency of the plant to 20–22% in comparison to industrial plants.