Elovich Equation Research Articles

Adsorption isotherm and kinetic study of gas-solid system of formaldehyde on oil palm mesocarp bio-char: Pyrolysis effect

The kinetic and isotherm studies of gas-solid system were represented by oil palm mesocarp bio-char as adsorbent and formaldehyde as adsorbate. Three kinetic model; i.e pseudo-first-order, pseudo-second-order and Elovich model and three isotherm model; i.e. Langmuir, Freundlich and Temkin isotherm were applied to evaluate the applicability of the equilibrium experimental data and the pyrolysis effect was studied. As a result, oil palm fiber carbonized at 500 °C and 700 °C was best presented by the Langmuir isotherm and oil palm mesocarp carbonized at 600 °C and 800 °C followed Temkin and Freundlich model, respectively. The formaldehyde adsorption was found favorable to happen at 25 °C with initial concentration of 0.5 ppm, 0.9 ppm, 0.75 ppm and 2.1 ppm as the Langmuir dimensionless constant, RL gave the value of 0 < RL < 1. Carbonization temperature of 500 °C, 600 °C, and 700 °C was kinetically presented by pseudo-first-order kinetic equation and carbonization temperature of 800 °C followed Elovich equation. As a conclusion, the pyrolysis of oil palm mesocarp does affect the isotherm and kinetic behavior of formaldehyde adsorption on oil palm char.

HEXAVALENT CHROMIUM ADSORPTION CAPABILITY ONTO CARBON BLACK: KINETIC AND THERMODYNAMIC ASPECTS

The adsorption rate and dynamic behaviour of the system are important factors in the process design and operation control. The aim of this study was to find a suitable kinetic model for the hexavalent chromium removal in a batch reactor. The experimental data were analyzed using four adsorption kinetic models – the pseudo first- and second-order equations, the Elovich equation and intraparticle diffusion equation – so as to determine the best fit equation for the adsorption of Cr(VI) onto the carbon black. The rate constants and related correlation coefficients for each kinetic model were calculated and discussed. Also, the predicted qe, cal values from the kinetic equations were compared with the experimental data. Results showed that the pseudo second- order equation provides the best correlation for the adsorption process, whereas the Elovich equation also good fits with the experimental data. The values of the thermodynamics parameters, including the energy of activation, suggest that physisorption is dominant for the adsorption of Cr(VI) onto the carbon black.

Toluene vapor sensing characteristics of novel copper(II), indium(III), mono-lutetium(III) and tin(IV) phthalocyanines substituted with 2,6-dimethoxyphenoxy bioactive moieties

This study presents the synthesis, characterization and toluene sensing properties of copper(II), indium(III) acetate, mono-lutetium(III) acetate and tin(IV) phthalocyanines substituted with 2,6-dimethoxyphenol bioactive groups at the peripheral and non-peripheral positions. The effects of the substituent’s position on the toluene vapor detection capabilities of these compounds were investigated. Adsorption data were analyzed by using first-order and Elovich equations in order to investigate the adsorption kinetics. It was found that the kinetics of the toluene adsorption strongly depends on the position of the substituent groups. Our results showed that the Elovich equation fits the experimental data well for non-peripherally substituted Pc based sensors, while the pseudo first-order model best describes the adsorption data for peripheral substituted Pc based sensors.

Removal of Levofloxacin from aqueous solution by Magnesium-impregnated Biochar: batch and column experiments

ABSTRACTAdsorption of levofloxacin (LEV) onto four types of magnesium (Mg)-impregnated biochars, fabricated via thermal pyrolysis of wood chips pretreated with MgSO4 was investigated. The Mg-impregnated biochars were characterized with various tools and techniques. Batch sorption experiments were conducted to determine the sorption kinetics and isotherms of LEV onto the Mg-impregnated biochars. The pseudo-second order kinetic model described the adsorption kinetic data better than the pseudo-first order kinetic model and the Elovich equation. Due to multi-mechanisms, the Freundlich model described the experimental isotherms better than the Langmuir model. The Langmuir maximum adsorption capacities of the Mg-impregnated biochars to LEV ranged from 7.38 to 25.2 mg g−1. In the fixed-bed column experiment, higher bed height and lower flow rate led to greater LEV removal. Findings from this work indicate that Mg-impregnated biochars can be used as an alternative adsorbent to effectively remove LEV from aqueous solutions.

Evaluation of Controlled Release Urea on the Dynamics of Nitrate, Ammonium, and Its Nitrogen Release in Black Soils of Northeast China.

Controlled release urea (CRU) is considered to enhance crop yields while alleviating negative environmental problems caused by the hazardous gas emissions that are associated with high concentrations of ammonium (NH4+) and nitrate (NO3−) in black soils. Short-term effects of sulfur-coated urea (SCU) and polyurethane-coated urea (PCU), compared with conventional urea, on NO3− and NH4+ in black soils were studied through the buried bag experiment conducted in an artificial climate chamber. We also investigated nitrogen (N) release kinetics of CRU and correlations between the cumulative N release rate and concentrations of NO3− and NH4+. CRU can reduce concentrations of NO3− and NH4+, and PCU was more effective in maintaining lower soil NO3−/NH4+ ratios than SCU and U. Parabolic equation could describe the kinetics of NO3− and NH4+ treated with PCU. The Elovich equation could describe the kinetics of NO3− and NH4+ treated with SCU. The binary linear regression model was established to predict N release from PCU because of significant correlations between the cumulative N release rate and concentrations of NO3− and NH4+. These results provided a methodology and data support for characterizing and predicting the N release from PCU in black soils.

Preparation of Zeolite F as Slow Release Fertilizers from K‐Feldspar Powder

AbstractInfluence of KOH concentration and reaction time on the synthesis of zeolite F from K‐feldspar, and the kinetics of potassium slow release from the product were studied. X‐ray diffraction (XRD), Fourier transformation infrared spectrometry (FTIR), and scanning electron microscopy (SEM) were applied to characterize the as‐synthesized samples. The XRD results indicate that there exist K−G zeolite (K2Al2SiO6⋅H2O) with hexagonal structure at the KOH concentration of 2 mol⋅kg−1 and zeolite F (KAlSiO4⋅1.5H2O) with tetragonal structure at 4–5 mol⋅kg−1. In terms of synthesis efficiency, crystallization time of 12 h was chosen as optimal condition. The surface area and pore diameter of zeolite F sample synthesized in 4 mol⋅kg−1 at 95 °C for 12 h were investigated by surface area analyzer, the values of which are 27 m2/g and 0.513 nm, respectively. Slow‐release testing results suggest that the potassium cumulative release fraction of zeolite F in water for 42 d is up to 68.97% and can be fitted well with Elovich equation.

Apoplastic and symplastic uptake of phenanthrene in wheat roots.

The contamination of agricultural crops by polycyclic aromatic hydrocarbons (PAHs) has drawn considerable attention due to their carcinogenicity, mutagenicity, and toxicity. However, the uptake process of PAHs in plant roots has not been clearly understood. In this work, we first study the radial uptake of phenanthrene in hydroculture wheat roots by vacuum-infiltration-centrifugation method. The concentration-dependent kinetics of apoplastic and symplastic uptake at phenanthrene concentrations of 0-6.72μM for 4h can be described with the Langmuir and Michaelis-Menten equations, respectively; whereas, their time-dependent kinetics at 5.60μM phenanthrene for 36h follow the Elovich equation. The apoplastic and symplastic uptake increases with temperature of 15-35°C. The apparent Arrhenius activation energies for apoplastic and symplastic uptake are 77.5 and 9.39KJmol-1, respectively. The symplastic uptake accounts for over 55% of total phenanthrene uptake, suggesting that symplast is the dominant pathway for wheat root phenanthrene uptake. Larger volume of symplast in roots and lower activation energy lead to the greater contribution of symplast to total uptake of phenanthrene. Our results provide not only novel insights into the mechanisms on the uptake of PAHs by plant roots, but also the help to optimize strategies for crop safety and phytoremediation of PAH-contaminated soil/water.

Removal of refractory organics from saline concentrate produced by electrodialysis in petroleum industry using bone char

In a scenario of hydric scarcity, water reuse is essential to minimize make-up; however, increased salinity comes along with recycling streams. Crystallization has been evaluated to remove dissolved ions; nevertheless, contaminants affect its efficiency. In this context, the removal of residual organics from the saline concentrate from electrodialysis applied for water reuse in a Brazilian petroleum refinery was investigated. Aiming at establishing a sustainable virtuous circle, bone char, a waste from food industry, 0.5–1.4 mm particle size, was used as adsorbent for refractory organics removal. Equilibrium adsorption time of 4 h was determined from batch experiments (through 72 h, at 25.0 ± 0.1 °C, pH 7.6 ± 0.5 and 200 ± 1 rpm, solid/liquid ratio of 10 g kg−1) in a shaker and a removal of 54% for dissolved chemical oxygen demand (COD) was observed. Adsorption kinetics (pseudo-first and pseudo-second order; Elovich equation) and equilibrium isotherms were evaluated. Pseudo-second order model for kinetics (R2 = 0.9993; k2 = 0.0184 mg−1 min−1; qe = 3.21 mg g−1) and Freundlich isotherm model best fitted to experimental data (R2 = 0.995), suggesting physisorption in multiple layers. The adsorbent thermal regeneration was evaluated (at 300, 500 and 700 °C, for 60, 120 and 180 min). Partial thermal regeneration was achieved at lower temperature and time demands (300 °C and 60 min—dissolved COD removal was around 40% after the first cycle of regeneration). Further investigation, including scaling-up and a cost-benefit analysis, is necessary in order to assess its use as a viable low-cost alternative for this type of effluent.

Simultaneous Dynamics and Kinetics of Soil Phosphorus Under Different Fertilizer Systems During Two-Growth Seasons of Maize

ABSTRACTThis study investigated phosphorus (P) dynamics and kinetics in calcareous soil under inorganic, organic, and integrated (inorganic+organic) fertilizer systems during two growing seasons of maize in two soil depths (0–0.15 and 0.15–0.30 m). A field experiment was conducted with 150, 300, and 400 kg ha−1 triple superphosphate (TSP), 7.5 and 15.0 ton ha−1 (on dry matter basis) farmyard manure (FYM), and integrated systems. In order to analyze Olsen P, soil samples were collected in 30-day-intervals after planting. The results showed that at the end of the two growing seasons of maize, the lowest magnitudes of Olsen P0–0.15 m were 6.0, 6.8, 7.4, and 7.6 mg kg−1 for the control, 7.5 FYM, 15 FYM, and 150 TSP, respectively. The highest magnitudes of Olsen P0–0.15 m were 12.4, 11.5, 11.4, and 11.1 mg kg−1 for 300 TSP+15 FYM, 400 TSP+7.5 FYM, 400 TSP+15 FYM, and 300 TSP+7.5 FYM, respectively. The same trends were observed for Olsen P0.15–0.30 m. Heterogeneous diffusion model demonstrated that Elovich equation could best describe the experimental data (mean; R2 = 0.98, SE = 0.29). The highest P supply rates (PSR) were 4.73, 3.91, and 3.86 mg kg−1day−1 (days after application) for 400 TSP, 400 TSP+15 FYM, and 300 TSP, respectively. The models of P supply capacity of soil could estimate P supply of soil under different fertilizer systems (R2 = 0.84–0.95). The present study improved the understanding of the capacity and rate of P supply by considering P uptake by grain maize. Fertilizer recommendations depend on the accessibility of fertilizer types suggested to help choose the best fertilizer systems.

Release and kinetics of arsenic and plumbum in the Songhua River surficial sediments

To estimate the pollution of As and Pb in the Songhua River which flows through the major rice-producing regions in China, the present study investigated the level and release of As and Pb in surficial sediments which collected from nine sites in Songhua River (M1-M9). The concentration of As and Pb was ranged as follows: As=3.104~15.01μg/g, Pb=20.10~37.42μg/g; the average concentration: As=6.466±3.077μg/g, Pb=28.88±5.077μg/g. By analysis vertically, the average concentration of As was 5.166±1.496μg/g in the upstream, 5.815±1.793μg/g in the midstream, and 9.716±4.977μg/g in the downstream. The average concentration of Pb was 27.83±4.552μg/g in the upstream, 28.66±6.333μg/g in the midstream, and 30.99±4.837μg/g in the downstream. It indicated that the concentration of As and Pb increased gradually from upstream to downstream. As existed mainly as insoluble state and Pb existed mainly as sulfide and organic combining state in surficial sediments, and the species of As and Pb could transform with the change of the circumstance. The release of quantity of As was higher than Pb. The pH of 6 was not conducive to the release of As and Pb. When the temperature was 35 and 6°C, the release of As and Pb in surficial sediments were restrained, respectively. Fumaric acid and citric acid played an important role in promoting the release of As, but not conducive to Pb. Furthermore, the reasonable aeration rate was beneficial to the release process of As and Pb in surficial sediment. By kinetic analysis, the Elovich equation (Ct=84.931-8.952lnt) could be used to describe the dynamic process of the release of As in a relatively short time. The Elovich equation (C t =2.724+1.3724lnt) and double constant rate equation (lnC T =1.4646+0.1522lnT) could well describe the dynamics process of the release of Pb.

Microwave assisted modification of activated carbons by organic acid ammoniums activation for enhanced adsorption of acid red 18

Three organic acid ammoniums (ammonium succinate (AS), ammonium tartrate (AT) and ammonium citrate (AC)) were employed to modify Phragmites australis (PA)-based activated carbons during phosphoric acid activation via microwave irradiation to improve acid red 18 (AR 18) removals from aqueous solutions. The physicochemical properties of the modified (PAC-AS, PAC-AT and PAC-AC) and unmodified carbons (PAC) were systematically characterized. The nitrogen content, pHiep and basic foundational groups of the modified carbons increased however their surface areas decreased after modification. FTIR and XPS analyses revealed that N-containing groups such as NH, CONH and NH2 were effectively introduced on modified carbons' surfaces. Although PAC-AS and PAC-AT had lower surface area than PAC, their adsorption capacity were higher due to larger amount of N-containing groups. The adsorption kinetic data were simulated well by the Elovich equation and the equilibrium data were best fit to the Freundlich model for all PACs. The adsorption of AR 18 on PACs decreased with increasing pH values. The maximum AR 18 adsorption capacity followed an order of PAC-AS (115.93mg/g)>PAC-AT (104.23mg/g)>PAC (90.52mg/g)>PAC-AC (57.99mg/g), indicating that AS and AT are promising activating agents for activated carbons to improve their AR18 adsorption performances.

Competitive sorption of nickel, copper, lead and cadmium on okra leaves (Abelmoschus esculentus)

In this study, potential of okra leaves for the removal of Ni(II), Cu(II), Pb(II) and Cd(II) from the mixed metal aqueous solution were evaluated. The data were analyzed by Freundlich, Langmuir, D-R, Flory-Huggins and Halsey adsorption models. Pseudo first order rate, Pseudo second order rate, Morris-Weber and Elovich equations were employed to understand the kinetics of the reaction. The characterization of the adsorbent was carried out by EDX and FTIR techniques. The order of maximum metal uptake calculated by D-R isotherm was Cu(II) &gt; Pb(II) &gt; Cd(II) and Ni(II), 453 mg g-1, 81 mg g-1, 13.82 mg g-1 and 1 mg g-1 respectively, with the energy of adsorption in the range of 9-15 for Ni(II) and Cd(II) expected for the ion exchange nature of adsorption and 7-8 for Cu(II) and Pb(II) showing the physical nature of adsorption. The calculated thermodynamic parameters like Gibbs free energy and enthalpy change demonstrate that adsorption process was spontaneous and endothermic in nature. Further it was observed that all four metal ions could be adsorbed at pH 6 with detection limits of 0.04-0.1 µg L-1. The method was successfully applied for the removal of these metal ions from the ground water, tap water and wastewater samples collected from different areas of Pakistan.

KINETICS OF SCANDIUM SORPTION BY IMPREGNATE CONTAINING PHOSPHINOXIDE

The kinetics of scandium sorption with impregnate-containing extractant – phosphine oxide based on hypercrosslinked polystyrene from nitric acid solutions was studied using a method of limited solution volume. A sample of sorbent obtained by impregnation contained 0.233 g extractant/g impregnate. Under batch conditions, the influence of temperature in the range 293-313 K on the kinetics of scandium sorption by impregnate was studied. It was revealed that the saturation of impregnate by scandium is established in 20-30 min. For the processing of integral kinetic scandium sorption curves, the pseudo-first and pseudo-second-order models, as well as the Elovich equation, were used. The values of the rate constants calculated from the pseudo-second-order model, describing the kinetic data with the best correlation coefficients (R2 0.931-0.995), reach (9.51-10.4) g∙(mmol∙min)-1. The activation energy of scandium sorption, calculated by an equation similar to the Arrhenius equation, is (2.8±0.2) kJ / mol. Due to the improved kinetic characteristics compared with traditional sorbents, hypercrosslinked polystyrene impregnates containing phosphine oxide can be used to extract of scandium from solutions formed during the processing of scandium-containing raw materials.Forcitation:Pyae Phyo Aung, Veselova O.A., Troshkina I.D. Kinetics of scandium sorption by impregnate containing phosphinoxide. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 28-30.

Inorganically modified clay minerals: Preparation, characterization, and arsenic adsorption in contaminated water and soil

The use of modified clay minerals for adsorbing arsenic (As) in contaminated soils is an underexplored area of research. The adsorption behavior of As onto inorganically modified smectite and kaolinite both in aqueous and soil media was studied. X-ray diffraction, infra-red spectroscopy, scanning and transmission electron microscopy studies confirmed successful modification of smectite through Fe-exchange and Ti-pillaring, and kaolinite through phosphate binding. The modified smectites were more efficient than phosphate-bound kaolinite in adsorbing As both in water and soil systems. Kinetic study revealed that the clay products reached adsorption equilibrium within 3h, and the data well fitted to the power function and simple Elovich equation (R2>0.90). The Freundlich isotherm model best described the As adsorption data (R2>0.86) of the modified clay products in both the systems. The Ti-pillared smectite exhibited the highest As adsorption capacity (156.54μgg−1) in the aqueous medium, while the Fe-exchanged smectite was the best material in the soil system (115.63μgg−1). The partition coefficient (Kd) and adsorption efficiency (%) data also maintained the similar trend. Precipitation of As and binuclear complex formation also took place in the soil system which made the metalloid non-labile as the time passed. The inorganically modified clay products reported here hold a great potential to adsorb As in contaminated groundwater, drinking water as well as soil.

Cr(VI) removal from aqueous solutions using aluminosilicate minerals in their Pb-exchanged forms

This work investigated the removal of Cr(VI) from aqueous solutions by employing Pb-modified zeolite, vermiculite and perlite as adsorbents. Natural zeolite and vermiculite exhibited high Pb2+ adsorption (~80% of the total Pb2+ concentration in solution), while perlite resulted in low lead adsorption (21%). Subsequently, the Pb-modified zeolite and vermiculite exhibited high Cr(VI) adsorption. The maximum Cr(VI) adsorption capacity as predicted by the Langmuir isotherm was 18.9mgg−1 for zeolite and 23.0mgg−1 for vermiculite. Langmuir was the isotherm equation that best fitted the experimental data. In terms of kinetics the Elovich equation represented the best fit to Cr(VI) adsorption on the studied modified minerals. The lowest mineral concentration that was tested (10gL−1) resulted in the highest solid phase equilibrium concentration. Desorption experiments were not effective since the desorption percent achieved with NaCl solution was very low (4–6%). Cr(VI) removal using Pb-modified minerals can be applied in the successive treatment of industrial wastewater first for lead and then for Cr(VI) removal.

Potential toxic trace element (PTE) contamination in Baoji urban soil (NW China): spatial distribution, mobility behavior, and health risk.

Rapid urbanization and industrialization may cause increased exposure levels to potential toxic trace elements (PTEs) and associated health risks for population living in cities. The main objectives of this study are to investigate systematically the occurrence, source, fate, and risk of PTE contamination from industrial influence in Baoji urban soil. Seven PTE levels (Pb, Zn, Cu, Cr, V, Sb, and As) were surveyed in 50 composite samples from Baoji urban soil by wavelength dispersive X-ray fluorescence spectrometry. Results reveal that the long-term industrial activities have increased PTEs Pb (409.20mg/kg mean value), Cu (107.19mg/kg mean value), Zn (374.47mg/kg mean value), and Sb (26.00mg/kg mean value) to enrich in urban soil at the different extents. The same results concur with the significant similarity of spatial distribution patterns of Pb, Zn, Cu, and Sb (slightly similar distribution) interpolated by GIS, implying a considerable Pb, Zn, Cu, and Sb contamination pool in urban soil disturbance from local metallic industrial activities. Whereas As in study area mainly controls parent material leaching and therefore has natural sources. Cr and V with the heterogeneous spatial distributions are possibly inclined to coal combustion sources. Those conclusions are also confirmed by the results of multivariate analysis. The chemical forms of PTEs fractionated by BCR three-stage sequential extraction procedure show that Pb and Cu are highly associated to the reducible phase (62.55 and 36.41%, respectively). However, Zn is highly associated to the oxidizable phase (33.68%), and a significant concentration is associated to acid and water extractable fractionation of 15.93% for Zn and 34.40% for Pb. In contrast, As, Cr, V, and Sb are mainly bound to the residual phase (>65% for all elements) with low concentrations retained to water extractable fractionation. The health risk assessed by a new classification Modified Integrate Risk Assessment Code (MI-RAC) reveals that the Pb poses the extremely high risk for human health than others. The results of PTE leaching in organic acids (artificial chelating agent and LMMOAs) indicate that low pH and more carboxyl groups of organic acid can quickly increase the PTEs release from soil and induce more mobility. By comparison, DTPA and EDTA are the effective extractant for Pb and Sb. The leaching kinetics of most PTEs are best described with the Elovich equation model and which involve the ligand exchange (LE) and ligand-enhanced dissolution (LED) two major process. It is a conclusion that long-term metallic industrial activities would accelerate the PTE accumulations in Baoji urban soil and enhance their mobility in a local scale. The considerable mobility and extremely high risk of Pb in Baoji ecoenvironment should be paid more attentions, and the phytoremediation with organic acid leaching assistant could be used to reduce total metal content of multiPTE contaminants in Baoji soils. The research will give the scientific knowledge for controlling the pollution of PTEs in urban soil and can be used as guidance to control the soil pollution in similar cities worldwide.

Leaching Kinetics of Hemimorphite in Ammonium Chloride Solution

The leaching kinetics of hemimorphite (Zn4Si2O7(OH)2·H2O) in ammonium chloride solution was presented in detail. Effects of stirring speed (150–350 rpm), leaching temperature (75–108 °C), particle size of hemimorphite (45–150 μm), and the concentration of ammonium chloride (3.5–5.5 mol/L) on the zinc extraction rate were studied. The zinc extraction rate enhanced slightly with the increase in stirring speed, but increased significantly with an increase in the leaching temperature and ammonium chloride concentration. Zinc extraction was enhanced significantly in the first 60 min with decreasing particle size, but had little effect on the leaching process after 60 min. Scanning electron microscopy (SEM) analysis showed that some silica gel formed in the leaching process was not separated from the hemimorphite surface, but covered some of the active particle surface. The Elovich equation successfully described the leaching kinetics of hemimorphite in ammonium chloride solution with an apparent activation energy of 405.14 kJ/mol at temperatures of 75–90 °C and 239.61 kJ/mol at temperatures of 95–108 °C, which is characteristic for a chemically-controlled process. Silica gel is generated at temperatures of 75–90 °C and decomposed into silica at temperatures of 95–108 °C.

Biosorption of cadmium ions from aqueous solution by modified Auricularia Auricular matrix waste

In order to reduce the harm of cadmium(II) to environment and health, the NaOH modified Auricularia Auricular matrix waste (AAMW) was used to adsorb cadmium(II) in aqueous solution. The cadmium(II) adsorption onto modified AAMW was pH and concentration-dependent, high pH and cadmium(II) initial concentration favored the adsorption. This biosorption underwent a rapidly physical process followed by a slowly chemical process and equilibrated at 60 min with a adsorption capacity of 35.51mg/g. The experimental data fitted well with Freundlich isothermal model and Elovich equation model. The amino, hydroxy, carboxy and phosphonate groups were responsible for cadmium(II) adsorption onto modified AAMW. Sodium hydroxide could remove the impurities on the adsorbent and provide more space for cadmium(II) binding as well as increase polarity of the adsorbent. The ion exchange also took place during the adsorption process. The adsorption capacity remained 14.02mg/g after three reuse cycles.

Kinetic Sorption of 2,4-Dichlorophenol and Rhodamine-B from Aqueous Solutions onto Modified Phragmites Australis

This study investigates the potential use of activated carbon prepared from Phragmites Australis for the removal of 2,4-dichlorophenol (DCP) and Rhodamine-B (RB) from aqueous solutions. P. Australis activated carbon (PAAC), a new adsorbent, was prepared from P. Australis by H3PO4 activation. The sorption behavior and the rate-controlling sorption step has been discussed from the pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion models. It was found that the adsorption of 2,4-DCP and RB onto PAAC both followed pseudo-second-order model. Adsorption mechanism studies revealed that the process followed both surface adsorption and particle diffusion. Accordingly, the activated carbon developed in this study is effective and practical for utilization in wastewater treatment for 2,4-DCP and RB removal.

The Release Characteristics of Cr(Ⅵ) in Contaminated Soil by Dynamic Simulation of Acid Rain

The release characteristics of Cr(â…¥) from contaminated soil, spiked with inorganic salts of Cr(â…¥),were investigated by dynamic leaching experiment in soil column with simulated acid rain. The soil samples were divided into five groups (i.e., A, B, C, D, E). Respectively, the contents of Cr(â…¥) were 100mg, 135mg, 170mg, 205mg, 240mg in per kilogram soil. In general, with the leaching time extension, the Cr(â…¥) concentration of leachate was declined obviously, repectively, A was from 0.55 to 0mg/L, B was from 1.12 to 0.12mg/L, C was from 2.65 to 0.62mg/L, D was from 1.84 to 2.27mg/L, E was from 1.87 to 0.12mg/L. The release rate of Cr(â…¥) was initially rapid and gradually declined after the fourth leaching. Cr(â…¥) loss percentage of leachate from soil was as high as 2.11%, 5.36%, 11.06%, 9.24%, 10.94% after leaching experiment. The results show that The release processes of Cr(â…¥) from soil were fitted with mathematical equations. The amended Elovich equation could better describe the release processes of Cr(â…¥).It implies that The release process of Cr(â…¥) is affected by a diffusion factor and reaction rate but not simply conformed to the first order kinetics. The pH values of leachate under simulated acid rain, whose pH value was 3.8, was in the range of 8.0 to 8.4. It implies that the pH values of leachate have nothing to do with Cr(â…¥) concentration in soil, and the soil has buffer capacity for H+. With this study and its results, the release of Cr(â…¥) in soil to ground water can be Predicted and the theoretical and technical support can be provided for ecological environment restoration.