• Environmental Engineering Research
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• v.16 no.2
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• pp.55-60
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• 2011

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.

• Membrane and Water Treatment
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• v.7 no.5
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• pp.403-416
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• 2016

The possibility of using carica papaya leaf powder for removal of copper from wastewater as a low cost adsorbent was explored. Different parameters that affect the adsorption process like initial concentration of metal ion, time of contact, adsorbent quantity and pH were evaluated and the outcome of the study was tested using adsorption isotherm models. A maximum of 90%-94.1% copper removal was possible from wastewater having low concentration of the metal using papaya leaf powder under optimum conditions by conducting experimental studies. The biosorption of copper ion was influenced by pH and outcome of experimental results indicate the optimum pH as 7.0 for maximum copper removal. Copper distribution between the solid and liquid phases in batch studies was described by isotherms like Langmuir adsorption and Freundlich models. The adsorption process was better represented by the Freundlich isotherm model. The maximum adsorption capacity of copper was measured to be 24.51 mg/g through the Langmuir model. Pseudo-second order rate equation was better suited for the adsorption process. A dynamic mode study was also conducted to analyse the ability of papaya leaf powder to remove copper (II) ions from aqueous solution and the breakthrough curve was described by an S profile. Present study revealed that papaya leaf powder can be used for the removal of copper from the wastewater and low cost water treatment techniques can be developed using this adsorbent.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.562-568
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• 2019

Cylindrical shape extrudates of calcium silicate hydrate (CSH) were prepared using different percentages of polyvinyl alcohol (PVA) / sodium alginate (SA) mixtures as binders and an aqueous solution containing 6% $H_3BO_3$ and 3% $CaCl_2$ was used as a cross linking agent. As the quantity of alginate increases, the phosphate removal efficiency and capacity were decreased. Among four different extrudate samples, the sample prepared by 8% PVA + 2% SA showed the highest phosphate removal efficiency (59.59%) and capacity (29.97 mg/g) at an initial phosphate concentration of 100 ppm and 2.0 g/L adsorbent dosage. Effects of the adsorbent dosage, contact time and initial phosphate concentration on the sample were further studied. The removal efficiency and capacity obtained by a 4.0 g/L adsorbent dose at an initial phosphate concentration of 100 ppm in 3 h were 79.38% and 19.96 mg/g, respectively. The experimental data of kinetic and isotherm measurements followed the pseudo-second-order kinetic equation and Langmuir isotherm model, respectively. These results suggested that the phosphate removal was processed via a chemisorption and a monolayer coverage of phosphate anions was on the CSH surface. The maximum adsorption capacity ($q_{max}$) was calculated as 23.87 mg/g from Langmuir isotherm model.

• Clean Technology
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• v.9 no.2
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• pp.81-85
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• 2003

A simple method of isotherm determination for HPLC is discussed. The equilibrium-dispersive model describing the behavior of elution peaks in HPLC for single component is solved numerically by using PDE solver Macsyma$^{(R)}$(Macsyma Inc., Arlington, MA, USA.) and compared to the experimental data obtained in overloaded isocratic chromatography with caffeine as model species. The effect of sample concentration and flow velocity on the band profiles of elution peaks are described.

• Journal of Environmental Health Sciences
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• v.24 no.1
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• pp.98-103
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• 1998

A study on the removal of mercury and lead by microorganisms, Saccharomyces cerevisiae and Aureobasidium pullulans, was performed, in which the comparison of adsorption model between these two heavy metals was done. The amounts of mercury removed were more than those of lead in both microorganisms. In case of mercury, the adsorption isotherm of S. cerevisiae was accorded with Langmuir model but A. pullulans was followed to Freundlich model. In the case of lead, however, the adsorption isotherm had opposite results. The adsorption rate of mercury to S. cerevisiae was faster than that of A. pullulans, but in the case of lead, it revealed contrary results. It seems, therefore, that the type of microorganisms used as biosorbents should be selected differently with the type of heavy metals removed for applying these to real adsorption process.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.45-51
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• 2010

Cadmium (Cd) adsorption by the activated carbon containing hydroxyapatite (HAP) was investigated. Cd adsorption with different HAP mass ranged from 10% to 30%. With more HAP, more Cd was adsorbed. These results suggest that the higher HAP dose causes an increase of the ion exchange potential in HAP sorbent. Kinetics and equilibrium studies were investigated in series of batch adsorption experiments. Langmuir and Freundlich isotherm models were fit to the equilibrium data and Cd adsorption on HAP sorbent were found to follow the Freundlich isotherm model well in the initial adsorbate concentration range. The simple kinetic model, the pseudo first order kinetic model and the pseudo second order kinetic model, were used to investigate the adsorption. The adsorption reaction of Cd followed the pseudo second order kinetic model, and the adsorption pseudo second order kinetic constants ($k_2$) increased with increasing initial HAP amounts onto activated carbon. Also, intraparticle diffusion model was used to investigate the adsorption mechanism between adsorbate and adsorbent in the aqueous phase. Surface adsorption reaction and intraparticle diffusion occur simultaneously Cd adsorption mechanism from aqueous phase in this study.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.505-512
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• 2017

The adsorption characteristics of Sr ion in aqueous solution was examined using zeolite NaA powder (Z-PA) and pellets (Z-BA). In batch experiment, the adsorption of Sr ions by Z-BA and Z-PA was well expressed by pseudo-second-order kinetic model than psedo-first-order kinetic model. Experimental isotherm results was well fitted to Langmuir isotherm model and the maximum adsorption capacities obtained from Langmuir isotherm model were 233.32 mg/g for Z-PA and 164.60 mg/g for Z-BA, respectively. The continuous experiment results showed that the total Sr ion uptake (q) increased, but the breakthrough time, effluent volume ($V_{eff}$) and total removal (R) of Sr ion decreased with the Sr ion concentration. The breakthrough curves obtained from the experiment was modeled by Thomas model.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.2
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• pp.27-34
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• 2014

Kinetic and isotherm properties of the cadmium adsorption onto calcium sand and granite soil were evaluated by batch experiments. The pHs of calcium sand and granite soil were 9.51 and 6.33, respectively, showing that the precipitation of heavy metals can be occurred due to the increase of pH when the calcium sand is used as an adsorbent. The pseudo-second-order model described the adsorption kinetics satisfactory with correlation coefficients over 0.999. The equilibrium adsorption capacities of calcium sand and granite soil were 2.10 and 2.16 mg/g, respectively. The adsorption isotherm followed the Freundlich isotherm model, indicating the cadmium adsorbed onto the heterogeneous surfaces of adsorbents.

• Macromolecular Research
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• v.16 no.6
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• pp.492-502
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• 2008

This study examined the adsorption of a synthetic cutting fluid and cutting fluid effluent on chitosan and SDS-modified chitosan, Chitosan and SDS-modified chitosan were prepared in form of beads and fibers. A series of batch experiments were carried out as a function of the initial concentration of cutting fluid, contact time and pH of the fluid. The contact angle study suggested that the SDS-modified chitosan was more hydrophobic than chitosan. The Zeta potential study showed that chitosan, SDS-modified chitosan and synthetic cutting fluid had a point of zero charge (PZC) at pH 7.8, 9 and 3.2, respectively. SDS-modified chitosan has a greater adsorption capacity than chitosan. The experimental results show that adsorption capacity of the cutting fluid on 1.0 g of SDS-modified chitosan at pH 3 and for a contact time of 120 min was approximately 2,500 g/kg. The adsorption capacity of chitosan and SDS-modified chitosan increased with decreasing pH. The Langmuir, Freundlich, and Brunauer Emmett and Teller (BET) adsorption models were used to explain the adsorption isotherm. The Langmuir isotherm fitted well with the experimental data of chitosan while the BET isotherm fitted well with the SDS-modified chitosan data. Pseudo first- and second-order kinetic models and intraparticle diffusion model were used to examine the kinetic data. The experimental data was fitted well to a pseudo second-order kinetic model. The significant uptake of cutting fluid on chitosan and SDS-modified chitosan were demonstrated by FT-IR spectroscopy, SEM and heat of combustion.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.5
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• pp.631-639
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• 2013

The removal of phosphate from surface water is becoming increasingly vital to prevent problems such as eutrophication, particularly near urban areas. Recent requirements to reduce high concentrations of phosphate rely on physicochemical methods and adsorbents that must be effective even under strict conditions. The phosphate removal efficiencies of two adsorbents, Fe-Mn-Si oxide and Fe-Mn oxide, were investigated and the data used to compare kinetics and isotherm models. The maximum adsorption capacities of the two adsorbents were 47.8 and 35.5 mg-$PO{_4}^{3-}/g$, respectively. Adsorptions in both cases were highly pH dependent; i.e., when the pH increased from 3 to 9, the average adsorption capacities of the two adsorbents decreased approximately 32.7 % and 20.3 %, respectively. The Freundlich isotherm model fitted the adsorption of Fe-Mn-Si oxide more closely than did the Langmuir model. Additionally, anionic solutions decreased adsorption because of competition with the anions in the adsorbing phosphate. Although affected by the presence of competing anions or a humic substance, Fe-Mn-Si oxide has better adsorption capacity than Fe-Mn oxide.