Comparison of Experimental and Simulated Adsorption of Binary Metal Ions using Sawdust Modified by Citric Acid
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and were evaluated as adsorbents for the removal of lead ions from aqueous solutions at room temperature. The effects of initial pH, mass of adsorbent, initial concentration of the metal, ionic strength and particle size were examined in batch experiments; pH exhibited a strong response to the levels of the lead (II) in the aqueous chemistry. Yet at the same time, and due to due to competition for the adsorption sites, and undesirable increase in ionic strength during the adsorption process was revealed. Moreover, in the equilibrium state, the mathematical adsorption model of Langmuir efficiently describes the competitive adsorption mechanism by both algae. The calculated parameters show a high adsorbent/adsorbate affinity, highlighting their potential utilization in the elimination of lead (II) from residual waters. Alga, lead (II), adsorption isotherm, pH, alginate, biosorption.
Biosorption
Langmuir adsorption model
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Buriti fibers were subjected to an alkaline pre-treatment and tested as an adsorbent to investigate the adsorption of copper, cadmium, lead and nickel in mono- and multi-element aqueous solutions, the results showed an increase in the adsorption capacity compared to the unmodified Buriti fiber. The effects of pH, adsorbent mass, agitation rate and initial metal ions concentration on the efficiency of the adsorption process were studied using a fractional 2(4-1) factorial design, and the results showed that all four parameters influenced metal adsorption differently. Fourier transform infrared spectrometry and X-ray fluorescence analysis were used to identify the groups that participated in the adsorption process and suggest its mechanisms and they indicated the probable mechanisms involved in the adsorption process are mainly ion exchange. Kinetic and thermodynamic equilibrium parameters were determined. The adsorption kinetics were adjusted to the homogeneous diffusion model. The adsorption equilibrium was reached in 30 min for Cu(2+) and Pb(2+), 20 min for Ni(2+) and instantaneously for Cd(2+). The results showed a significant difference was found in the competitiveness for the adsorption sites. A mathematical model was used to simulate the breakthrough curves in multi-element column adsorption considering the influences of external mass transfer and intraparticle diffusion resistance.
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Fractional factorial design
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With the aim of removing binary metal ions from aqueous solutions, the adsorption characteristics of sawdust modified with citric acid are investigated using adsorption kinetics and isotherms in both an experiment and a numerical simulation. The adsorption of metal ions is characterized by the competitive adsorption in binary metal ion systems that results from the stability constants between metal ions and citrate in the modified sawdust. These findings suggest that competitive adsorption and the affinities of the metal ion adsorbents play important roles in the removal of metal ions and that the numerical simulation can predict the adsorption characteristics of the modified sawdust.
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Surface reaction methodology was employed for the optimization of cadmium removal onto sawdust with respect to various physico-chemical parameters. FT-IR was principally employed for the assessment of the chemical structure of sawdust. The biosorption equilibrium data were best represented by Khan and Langmuir isotherms. The monolayer sorption capacity obtained from Langmuir model was found to be 41.21 mg/g. Biosorption showed pseudo second order rate kinetics at different initial concentration of Cd(II). The intraparticle diffusion study indicated that film diffusion may be involved in the current study. Thermodynamic parameters showed that the sorption process is exothermic and non-spontaneous.
Biosorption
Sawdust
Langmuir adsorption model
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Adsorption of heavy metals by sawdust was investigated to evaluate the effectiveness of using sawdust to remove heavy metals from aqueous solutions.Kinetic and isotherm studies were carried out by considering the effects of initial concentration and pH.The adsorption isotherms of heavy metals fitted the Langmuir or Freundlich model reasonably well.The adsorption capacity of metal was in the order Pb 2+ > Cu 2+ > Zn 2+ .A high concentration of co-existing ions such as Ca 2+ and Mg 2+ depressed the adsorption of heavy metal.Adsorption data showed that metal adsorption on sawdust follows a pseudo-second-order reaction.Kinetic studies also indicated that both surface adsorption and intraparticle diffusion were involved in metal adsorption on sawdust.Column studies prove that sawdust could be effective biosorbent for the removal of heavy metals from aqueous phase.
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In this study, the competitive separation of lead, cadmium, and nickel ions from aqueous solutions using a commercial activated carbon (AC) has been investigated and optimized using response surface methodology (RSM). The optimal conditions to reach the highest adsorption capacity for these metals were found as follows: initial pH = 6.3, temperature = 56.8°C, and shaking speed = 308 rpm. Under these conditions, the sequence of adsorption capacity toward the metal ions was as follows: Pb (II): 9.44 mg g−1 > Cd (II): 9.37 mg g−1 > Ni (II): 4.52 mg g−1. The effect of shaking speed on the adsorption capacity of AC was higher than the effects of the initial pH and temperature, indicating the more important role of physisorption than chemisorption in the adsorption of these metal ions. This was confirmed by the results of thermodynamic studies. The equilibrium adsorption data were fitted to the Freundlich, Langmuir adsorption isotherm models and the Dubinin–Radushkevich model parameters were evaluated. All the models were tested and all were shown to represent the experimental data satisfactorily. The thermodynamic parameters such as ΔH, ΔS, and ΔG were computed from the experimental data. These values show that the adsorption is endothermic and spontaneous. The positive value of ΔS° indicates increasing of randomness at the solid/liquid interface during the adsorption of metal ions on AC.
Physisorption
Endothermic process
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Langmuir adsorption model
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In this work, the efficiency of walnut shell as a low-cost and natural adsorbent for removing metal ions from aqueous solution and electroplating wastewater has been studied. Batch experiments were conducted to study the effect of some parameters such as contact time, initial concentration, solution pH and temperature on the adsorption of Cu(II), Zn(II) and Cd(II) by walnut shell. Langmuir and Freundlich models were employed for the mechanistic analysis of experimental data and the observation reveals that in our system adsorption follows the Langmuir isotherm. The maximum adsorption capacity of Cu(II), Zn(II) and Cd(II) were found to be 14.53, 7.47 and 7.29 mg/g, respectively. The pseudo-first-order and pseudo-second-order models were employed for kinetic analysis of adsorption process. It was found that adsorption process follows pseudo-second-order kinetics. The adsorption process was subjected to thermodynamic study revealing that adsorption of these metals on the natural adsorbent was spontaneous and endothermic in nature. According to the experimental investigation, walnut shell seems to be an effective, natural, low-cost and alternative adsorbent for the removal of these metal ions from aqueous solutions. The efficacy of walnut shell in the treatment of effluent from electroplating industry has been explored and the results have been found encouraging.
Endothermic process
Langmuir adsorption model
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Biosorption
Endothermic process
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In the present study, chemically modified Aleppo pine (Pinus halepensis Miller) sawdust was used for removal of phosphate from water. Biosorbent preparation process included size fractionation, extraction for surface activation, acid prehydrolysis, and treatment with urea. Sorption of phosphate ions onto biosorbent was studied using the batch technique. The effect of different parameters such as contact time, adsorbate concentration, and temperature was investigated. The adsorption kinetics data were best described by the pseudo-second-order rate equation, and equilibrium was achieved after 40 min. The Langmuir and Freundlich equations for describing adsorption equilibrium were applied to data. The constants and correlation coefficients of these isotherm models were calculated and compared. The adsorption isotherms obey the Freundlich equation. The thermodynamic parameters like free energy, enthalpy and entropy changes for the adsorption of phosphate ions have been evaluated and it has been found that the reaction was spontaneous and endothermic in nature. The low value of activated energy of adsorption, 3.088 kJ/mol, indicates that the phosphate ions are easily adsorbed on the sawdust. Results suggest that the prepared chemically modified Aleppo pine sawdust has potential in remediation of contaminated waters by phosphate
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