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1.
This paper presents a study on the batch adsorption of a basic dye, methylene blue (MB), from aqueous solution onto ground hazelnut shell in order to explore its potential use as a low-cost adsorbent for wastewater dye removal. A contact time of 24 h was required to reach equilibrium. Batch adsorption studies were carried out by varying initial dye concentration, initial pH value (3–9), ionic strength (0.0–0.1 mol L?1), particle size (0–200 μm) and temperature (25–55°C). The extent of the MB removal increased with increasing in the solution pH, ionic strength and temperature but decreased with increase in the particle size. The equilibrium data were analysed using the Langmuir and Freundlich isotherms. The characteristic parameters for each isotherm were determined. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were represented well by Langmuir isotherm equation. The maximum adsorption capacities for MB were 2.14?×?10?4, 2.17?×?10?4, 2.20?×?10?4 and 2.31?×?10?4 mol g?1 at temperature of 25, 35, 45 and 55°C, respectively. Adsorption heat revealed that the adsorption of MB is endothermic in nature. The results indicated that the MB strongly interacts with the hazelnut shell powder.  相似文献   

2.
Removal of arsenic from water reservoirs is the issue of great concern in many places around the globe. As adsorption is one of the most efficient techniques for treatment of As-containing media, thus the present study concerns application of iron oxides-hydroxides (akaganeite) as adsorbents for removal of this harmful metal from aqueous solution. Two types of akaganeite were tested: synthetic one (A) and the same modified using hexadecyltrimethylammonium bromide (AM). Removal of As was tested in batch studies in function of pH, adsorbent dosage, contact time, and initial arsenic concentration. The adsorption isotherms obey Langmuir mathematical model. Adsorption kinetics complies with pseudo-second-order kinetic model, and the constant rates were defined as 2.07?×?10?3and 0.92?×?10?3 g mg?1 min?1 for the samples (A) and (AM), respectively. The difference was caused by significant decrease in adsorption rate in initial state of the process carried out for the sample AM. The maximum adsorption capacity achieved for (A) and (AM) akaganeite taken from Langmuir isotherm was 148.7 and 170.9 mg g?1, respectively. The results suggest that iron oxides-hydroxides can be used for As removal from aqueous solutions.  相似文献   

3.
Cattle manure vermicompost has been used for the adsorption of Al(III) and Fe(II) from both synthetic solution and kaolin industry wastewater. The optimum conditions for Al(III) and Fe(II) adsorption at pH?2 (natural pH of the wastewater) were particle size of ≤250?µm, 1 g/10 mL adsorbent dose, contact time of 4 h, and temperature of 25°C. Langmuir and Freundlich adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R 2 values from 0.90 to 0.98. In synthetic solution, the maximum adsorption capacity of the vermicompost for Al(III) was 8.35 mg g?1 and for Fe(II) was 16.98 mg g?1 at 25°C when the vermicompost dose was 1 g 10 mL?1, and the initial adjusted pH was 2. The batch adsorption studies of Al(III) and Fe(II) on vermicompost using kaolin wastewater have shown that the maximum adsorption capacities were 1.10 and 4.30 mg g?1, respectively, at pH?2. The thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous.  相似文献   

4.
The kinetics and mechanism of methylene blue adsorption onto raw pine cone biomass (Pinus radiata) was investigated under various physicochemical parameters. The extent of the methylene blue dye adsorption increased with increases in initial dye concentration, contact time and solution pH but decreases with the amount of adsorbent, salt concentration and temperature of the system. Overall the kinetic studies showed that the methylene blue adsorption process followed pseudo-second-order kinetics among various kinetic models tested. The different kinetic parameters including rate constant, half-adsorption time and diffusion coefficient are determined at different physicochemical conditions. Equilibrium data were best represented by Langmuir isotherm among Langmuir and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine cone biomass was 109.89 mg/g at 30°C. The value of separation factor, R L, from Langmuir equation and Freundlich constant, n, both give an indication of favourable adsorption. Thermodynamic parameters such as standard Gibbs free energy (?G 0), standard enthalpy (?H 0), standard entropy (?S 0) and the activation energy (A) were calculated. A single-stage batch absorber design for the methylene blue adsorption onto pine cone biomass has been presented based on the Langmuir isotherm model equation.  相似文献   

5.
Phosphorus is one of the key elements causing lake eutrophication. This paper deals with phosphate removal by Sponge iron in batch and fixed-bed operation. Isotherm and kinetic studies are conducted. The isotherm data is described by the Freundlich and Langmuir model, while the kinetic data of adsorption is fitted by the pseudo-second-order kinetic model. The saturated adsorption capacity of Langmuir isothermal equation is about 3.25 mg/g. The concomitant anions have adverse effect on phosphate adsorption and the effects follow the order: NO3??>?Cl??>?SO42?. The phosphate adsorption capacities of SI were improved significantly under the acidic condition. The results of the fixed-bed operation show that, with the increase of the influent phosphate concentrations, the breakthrough curve becomes steeper while the break point time decrease. According to the Adams–Bohart model, the critical height of the column decrease from 0.135 to 0.105 m when the contact time increased from 10 to 30 min with the influent concentration of 1.0 mg/L. According to BDST model, the critical bed depth is 0.15 m when the influent concentration of phosphate is 1.0 mg/L and the contact time (h) is 20 min.  相似文献   

6.
The application of magnetite-immobilized chitin in pentachlorophenol (PCP) removal was demonstrated in this study. The physicochemical parameters for immobilization of chitin by magnetite, and for PCP adsorption using magnetite-immobilized chitin were optimized. For chitin immobilization, the optimized conditions were: magnetite to chitin (m:c) ratio at 1:2, initial pH 6, 25°C, 200 rpm and 60 min in batch system. The immobilization efficiency (IE) was 99.4% and immobilization capacity (IC) was 2.0 mg chitin mg?1 magnetite. High initial pH (pH?>?11) and temperature (>30°C) lowered the IE and IC. For PCP (10 mg l?1) adsorption, the optimized conditions were: 1,500 mg l?1 immobilized chitin, initial pH 6, 25°C, 200 rpm and 60 min in batch system. The removal efficiency (RE) was 57.9% and removal capacity (RC) was 5.4 mg g?1. The adsorption ability of immobilized chitin decreased with pH and temperature increased. However, increasing the amount of immobilized chitin (24,000 mg l?1) can increase the RE up to 92%. Both chitin immobilization and PCP adsorption exhibited Langmuir and Freundlich adsorption isotherms. Results in this study indicated that magnetite-immobilized chitin was a cost-effective and environmental friendly adsorbent to remove environmental pollutants such as PCP.  相似文献   

7.
Methylene Blue Adsorption onto Water Hyacinth: Batch and Column Study   总被引：1，自引：0，他引：1  
The adsorption of methylene blue cationic dye by water hyacinth root was studied in a batch system. The experimental data isotherms were analyzed using the Langmuir and Freundlich equations. The monolayer adsorption capacity for methylene blue dye was found as 0.187?kg?kg?1. Three kinetic models (the pseudo-first order, the pseudo-second order, and the unified approach) were used to calculate the adsorption rate constants. The kinetic data along with equilibrium constants (maximum monolayer capacity and Langmuir constant) fitted well with unified approach model for different initial concentrations, and the rate constants were determined. Laboratory column experiments were conducted to evaluate the performance of water hyacinth root for methylene blue sorption under dynamic flow conditions. Breakthrough curves were plotted for the methylene blue adsorption on the adsorbent using continuous flow column operation by varying the bed height (0.06?C0.12?m) and the feed concentrations (0.1?C0.2?kg?m?3). Different column design parameters, such as depth of exchange zone, adsorption rate, and adsorption capacity, were calculated. At the end, an attempt has also been made to model the data generated from column studies using the empirical relationship based on Bohart?CAdams model.  相似文献   

8.

Purpose

Anion exchange resin has been shown to be efficient for adsorption of humic acid (HA). However, the mechanism of the effect(s) of the molecular weight (MW) of HA on the adsorption by anion exchange resin needs to be further explored. The objective of this work was to investigated the effect(s) of HA MW on their adsorption and desorption behavior by interacting with anion exchange resin.

Materials and methods

HA fractions with different MW were obtained by ultrafiltration and characterized. For adsorption kinetic study, the magnetic polyacrylic anion exchange resin (NDMP) was shaken with each HA fraction. The amounts of HA in the solutions at different sampling times were obtained by measurement of the total organic carbon. For isotherm study, batch experiments were performed to obtain the isotherms of each HA fractions. The effects of pH value and the regeneration efficiency for HA fractions with different MW were all investigated.

Results and discussion

The characterization reveals that aromaticity of HA increases as the MW rises, while the negative charge follows the order: HA3 (2,500–1,000 Da)?>?HA4 (>10,000 Da)?>?HA2 (1,000–2,500 Da)?>?HA1 (<1,000 Da). The adsorption amount of HA increases as the negative surface charge rises. Thus, HA3 has the largest adsorption amount by NDMP resin among HA fractions, while the adsorption amount of HA1 is the smallest. HA2 adsorption could be modeled by Freundlich equation, suggesting the interaction between HA2 and NDMP is a heterogeneous process. However, the adsorption isotherms of HA3 and HA4 were both better described by Langmuir equation than Freundlich equation. In addition, the resin fouling follows the order: HA2?>?HA1?>?HA4?>?HA3.

Conclusions

The aromaticity of HA freactions increases as MW rises. HA fractions with 1,000?–?2,500 Da have the largest surface negative charge, while the fractions with MW lower than 1,000 Da are almost electroneutral. The adsorptions of HA fractions onto NDMP suggest there is little effect of size exclusion on adsorption, and the adsorption behavior mainly depends on the negative charge of HAs.  相似文献   

9.
The batch sorption experiments were carried out using a novel adsorbent, freshwater macrophyte alligator weed, for the removal of basic dye malachite green from aqueous solution. Effects of process parameters such as initial solution pH, contact time, adsorbent concentration, particle size, and ion strength were investigated. The adsorbent was characterized by FT-IR. The adsorption of malachite green by alligator weed was solution pH dependent. The adsorption reached equilibrium at 240 min for two particle size fractions. The pseudo-first-order equation, Ritchie second-order equation, and intraparticle diffusion models were tested. The results showed that adsorption of malachite green onto alligator weed followed the Ritchie second-order equation very well and the intraparticle diffusion played important roles in the adsorption process. The Langmuir and Freundlich equations were applied to the data related to the adsorption isotherms and the observed maximum adsorption capacity (q max) was 185.54 mg g?1 at 20°C according to the Langmuir model. The effects of particle size, adsorbent concentration, and ionic strength on the malachite green adsorption were very marked. The alligator weed could serve as low-cost adsorbents for removing malachite green from aqueous solution.  相似文献   

10.
Effluents containing phosphorous as phosphate ions are frequently discharged in freshwater resources contributing to the eutrophication and directly interfering in the biological equilibrium. Clam shell residues and sewage sludge were combined for preparing efficient adsorbents for phosphate removal from aqueous medium. The adsorbents were characterized before and after adsorption testing, and the adsorption equilibrium and kinetics were investigated. Phosphate removal of 89?±?1% was attained for samples prepared with 0.1?< X <?1.0, where X corresponds to sewage sludge/clam shell mass ratio. The analyses of the experimental errors indicated that the phosphorous removal followed the Elovich kinetic model, which describes adsorption in very heterogeneous surfaces. On the other hand, the best modelling was achieved using the Koble–Corrigan isotherm model, which incorporate different aspects of both Langmuir and Freundlich isotherms to represent the equilibrium data. The observed adsorption capacity (21.4 mgP g?1) are comparable or greater to that observed for other adsorbents described in the literature.  相似文献   

11.
Three novel composite adsorbents, sulfate-coated zeolite (SCZ), hydrotalcite (SCH), and activated alumina (SCAA), were characterized and employed for the removal of phosphate from aqueous solution using equilibrium and kinetic batch experiments. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectrum were used to study the surface characteristics of the coated layer. Equilibrium tests showed that the adsorption of phosphate followed both Langmuir and Freundlich isotherms. The powder-type SCZ was better for phosphate removal (maximum binding energy, ???=?111.49?mg?g?1) compared to hydrotalcite and activated alumina. The adsorption of phosphate was considered to take place mainly by ion exchange. The kinetic data followed a pseudo-second-order kinetic model. The initial adsorption of phosphate onto the sulfate-coated adsorbents was fast, indicating that the sulfate-coated materials developed in this study can be used as promising adsorbents for the removal of phosphate from wastewater or sewage.  相似文献   

12.
A highly effective zirconium-modified activated sludge (Zr(IV)-AS) adsorbent was prepared from activated sludge and applied to remove phosphate from aqueous solutions by batch and column experiments. Characterized results revealed that zirconium was successfully loaded onto the activated sludge (AS), and the specific surface area and pore volume were substantially improved after zirconium loading on the AS. Zr(IV)-AS exhibited a high adsorption affinity for phosphate and the maximum adsorption amount was 27.55 mg P·g?1 at 25 °C. Adsorption isotherms of phosphate could be described by the Langmuir model, and the adsorption kinetics were well described by the pseudo-second-order model. Phosphate adsorption on Zr(IV)-AS increased monotonically with decreasing solution pH. The presence of SO42? in water resulted in slightly decreased phosphate adsorption on the adsorbent even at a high concentration (25 mmol/L), and a greater influence of HCO3? on adsorption could be ascribed to the increased solution pH with the addition of the HCO3?. Column adsorption experimental results showed that the adsorbent has excellent phosphate adsorption properties and that the effluent can meet the requirement of phosphorus in the national wastewater discharge standard of China. Phosphate-saturated Zr(IV)-AS can be effectively desorbed in 0.1 mol L?1 NaOH solution, and the regenerated adsorbent still possessed the high capacity. The adsorption between the adsorbent and the phosphate is due to the electrostatic interaction and anionic exchange at the surface of the Zr(IV)-AS. Furthermore, this approach provides a possibility of treating wastewater with waste and has the potential for industrial applications for the removal of phosphate from wastewater.  相似文献   

13.
In the present work, we have applied a green method for the synthesis of silver nanoparticles (AgNPs) onto amino-functionalized silica using Nigella sativa (black seed) aqueous extract as an eco-friendly and efficient reducing agent. The factors influencing the functionalization of silica and AgNPs loading have been considered. The samples were characterized by elemental analysis, FTIR, XRD, TGA, SEM, and EDX and used for the removal of indigo carmine (IC) dye from aqueous solution. The mean particle size of immobilized AgNPs was calculated from the XRD pattern using the Scherrer equation and is equal to about 26 nm. Adsorption experiments were carried out as batch studies at different contact times, temperature, adsorbent dosage, and initial dye concentrations. The IC adsorption equilibrium was attained after about 20 min of contact time. The equilibrium data shows that the Langmuir model was more reasonable to depict the IC adsorption, and the maximum adsorption capacity of IC is 73.05 mg/g. Based on the kinetic analysis, the adsorption process follows a pseudo-second-order equation. The estimation of the thermodynamic parameters such as the Gibbs free energy, entropy, and enthalpy changes of the adsorption process indicated the feasibility and endothermic nature of IC adsorption. The modified surface was found to be extremely stable in the aqueous medium, and no significant leaching of AgNPs was observed. Thus, immobilization of AgNPs may advance reuse, reduce environmental risks associated with leaching of AgNPs, and enhance cost-effectiveness.  相似文献   

14.
In the present work, a biosorbent was produced through the alkaline washing of Brazilian ironwood fruits. Infrared and thermogravimetric analyses showed changes in the obtained biosorbent with the removal of extractives, whose micrograph presents a more fibrous structure for the treated material. The biosorption behavior of the methylene blue dye shows efficiency at pH above five, and at alkaline pH, it reaches removal efficiency of up to 90% for five successive cycles. Adsorption kinetics is fast and fits the pseudo-second-order model, which, with the best fit of the Langmuir isotherm model, indicates a chemical adsorption mechanism. The thermodynamic trials express the spontaneity of biosorption and enthalpy and entropy variations of ??10.47 kJ mol?1 and 51.84 J mol?1 K?1, respectively. The maximum biosorption capacity is of 125.2 mg g?1 for the temperature of 25 °C, consisting in a low-cost alternative for the removal of this type of contaminant from an aqueous medium.  相似文献   

15.
Tamarind fruit shell was used as a low-cost biosorbent for the removal of methylene blue from aqueous solution. The various factors affecting adsorption, such as agitation, pH, initial dye concentration, contact time, and temperature, were investigated. The dye adsorption capacity was strongly dependent on solution pH as well as temperature. The Langmuir isotherm model showed good fit to the equilibrium adsorption data, and the maximum adsorption capacity obtained was 1.72 mg g?1 at 303 K. The kinetics of adsorption followed the pseudo-second-order model and the rate constant increased with increase in temperature, indicating endothermic nature of adsorption. The Arrhenius equation was used to obtain the activation energy (E a) for the adsorption system. The activation energy was estimated to be 19.65 kJ mol?1. Thermodynamic parameters such as Gibbs free energy (ΔG 0), enthalpy (ΔH 0), and entropy (ΔS 0) were also investigated. Results suggested that adsorption of methylene blue onto tamarind fruit shell was a spontaneous and endothermic process. The present investigation suggests that tamarind fruit shell may be utilized as a low-cost adsorbent for methylene blue removal from aqueous solution.  相似文献   

16.
Abstract

Organic anions affect solute mobility in soils. This study evaluated citrate and oxalate adsorption (0 to 4 mmol L?1, soil–solution 1∶100, pH 5.5, ionic strength 30 mmol L?1 as NaCl, 72‐h reaction) and desorption (pH 5.5, 30‐mmol L?1 NaCl, 72 h) on A‐ and B‐horizon samples of two Brazilian Oxisols. Langmuir and Freundlich isotherms were used to assess adsorption maximum, distribution coefficients (Kf, Ku), and buffer index. Adsorption maximums (mol kg?1) for red Latossol‐A, red Latosol‐B, red‐yellow Latosol‐A, and red‐yellow Latosol‐B horizons follow: citrate 0.0318, 0.0272, 0.0289, 0.0392; oxalate 0.0641, 0.0329, 0.0538, 0.0380. Kf (mol1?1/n kg?1 L1/n) follows: citrate 0.3550, 0.3781, 0.4211, 0.2024; oxalate 1.0916, 0.0637, 1.8228, 0.0922. Buffer index (mol kg?1)(mol kg?1)?1 follows: citrate 0.0841, 0.0756, 0.0738, 0.0264; oxalate 0.3787, 0.0862, 0.3233, 0.1082. Both anions showed great affinity for variable‐charge soils. The distribution curves for Ku showed higher adsorption energy in B‐ than in A‐horizons.  相似文献   

17.
The adsorption of Cu(II) ions by sodium-hydroxide-treated Imperata cylindrica (SoHIC) leaf powder was investigated under batch mode. The influence of solution pH, adsorbent dosage, shaking rate, copper concentration, contact time, and temperature was studied. Copper adsorption was considered fast as the time to reach equilibrium was 40–90 min. Several kinetic models were applied and it was found that pseudo-second-order fitted well the adsorption data. In order to understand the mechanism of adsorption, spectroscopic analyses involving scanning electron microscope (SEM) coupled with energy-dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectrophotometer were carried out. Ion exchange was proven the main mechanism involved as indicated by EDS spectra and as there was a release of light metal ions (K+, Na+, Mg2+, and Ca2+) during copper adsorption. Complexation also occurred as demonstrated by FTIR spectra involving hydroxyl, carboxylate, phosphate, ether, and amino functional groups. The equilibrium data were correlated with Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. Based on Langmuir model, the maximum adsorption capacity was recorded at the highest temperature of 310 K, which was 11.64 mg g?1.  相似文献   

18.
In this study, activated red mud was used to develop an effective adsorbent in order to remove a toxic azo dye (tartrazine E102) from aqueous solutions. To increase the adsorption capacity, the red mud was activated by acid-heat treatment using 20 wt.% HCl (RM-HCl). To establish the optimum operating parameters, the influence of pH, adsorbent dose, contact time, initial dye concentration, and stirring rate was investigated. The adsorption equilibrium was studied using Langmuir, Freundlich, Dubinin-Radushkevich, Temkin isotherm models, and the characteristic parameters for each adsorption isotherm were determined. The kinetics of the adsorption process was analyzed by means of pseudo-first-order and pseudo-second-order models. The maximum removal efficiency obtained under optimum conditions was 84.72%. These results were in accordance with the isotherm and kinetic data. The results suggested that tartrazine adsorption process follows the pseudo-second-order kinetic model and also that fits Langmuir isotherm model. The maximum monolayer adsorption capacity was 136.98 mg/g.  相似文献   

19.
Sugarcane bagasse soot is an agro-industrial residue rich in carbon that can be transformed into value-added materials, such as activated carbons. Therefore, this work aimed at producing activated carbon from sugarcane bagasse soot, using CO2 at 800, 850, and 900 °C, and investigating its efficiency to adsorb methylene blue as model contaminant. The results showed that the surface area and pore volume increased in the obtained carbons, with high specific areas (up to 829 m2/g), and the isotherms of the N2 adsorption describe mesoporous materials. The morphology of the prepared activated carbons showed that sugarcane bagasse soot and the activated carbons kept the fibrous structure of sugarcane bagasse, but after activation, they have cavities that resemble a honeycomb. Adsorption studies with methylene blue dye showed that the activation process resulted in adsorption capacities up to 11 times higher than sugarcane bagasse soot, which is comparable with commercial activated carbon. Dye adsorption kinetics could be described by a pseudo-second-order dependency in the studied materials, and the adsorption isotherms were better fitted by the Langmuir model. It is emphasized that cost-effective materials that are similar to commercial activated carbon were obtained.  相似文献   

20.
The adsorption capacity of pine tree leaves for removal of methylene blue (MB) from aqueous solution was investigated in a batch system. The effects of the process variables, such as solution pH, contact time, initial dye concentration, amount of adsorbent, agitation speed, salt concentration, and system temperature on the adsorption process were studied. The extent of methylene blue dye adsorption increased with increase in initial dye concentration, contact time, agitation speed, temperature, and solution pH but decreased with increased in amount of adsorbent and salt concentration. Equilibrium data were best described by both Langmuir isotherm and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine tree leaves biomass was 126.58?mg/g at 30?°C. The value of separation factor, R L , from Langmuir equation and Freundlich constant, n, both give an indication of favorable adsorption. The intrapartical diffusion model, liquid film diffusion model, double exponential model, pseudo-first and second order model were used to describe the kinetic and mechanism of adsorption process. A single stage bath adsorber design for the MB adsorption onto pine tree leaves has been presented based on the Langmuir isotherm model equation. Thermodynamic parameters such as standard Gibbs free energy (??G 0), standard enthalpy (??H 0), and standard entropy (??S 0) were calculated.  相似文献   

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