• Journal of the Korean GEO-environmental Society
• /
• v.15 no.12
• /
• pp.61-69
• /
• 2014

Carboxymethyl-${\beta}$-cyclodextrin (${\beta}$-CMCD), as a biodegradable surfactant with hydrophobic and hydrophilic properties, has potential advantages of being applicable to the simultaneous treatment of multiple contaminated soils. In this study, the desorption behaviors of r adionuclides such as cobalt (Co), strontium (Sr), and cesium (Cs) from the soil contaminated with them were experimentally investigated and the effectiveness of CMCD as a desorbent was evaluated. The desorption equilibrium of used radionuclides could be achieved within 1~3 hr and the desorption ratio from kaolin was higher than that from natural soil. The addition of CMCD of 2 g/L increased the desorption ratio by 5~20 % and the desorption ratio of used r adionuclides was shown in the order of Co > Cs > Sr. The experimental desorption data were fitted successfully by pseudo-second order kinetic model and the desorption rate of the r adionuclides was shown in the order of Cs > Co > Sr. Hysteresis between adsorption and desorption of the r adionuclides, as shown in the order of Sr > Co > Cs, increased as the desorption rate decreased. Consequently, it could be considered that the desorption rate was one of the significant factors of the hysteresis. The addition of CMCD as desorbent increased the amount of desorbed radionuclides and decreased the hysteresis. However, the CMCD could not completely desorb the radionuclides from soils even though the excess of CMCD was added.

• Applied Chemistry for Engineering
• /
• v.28 no.6
• /
• pp.663-669
• /
• 2017

Activated carbons were prepared from waste citrus peels using KOH, NaOH, and $ZnCl_2$ as activating chemicals. They were prepared at optimal conditions including the chemical ratio of 300%, activation time of 1.5h, and activation temperature of $900^{\circ}C$ for KOH, $700^{\circ}C$ for NaOH, and $600^{\circ}C$ for $ZnCl_2$, which were named as ACK, ACN, and ACZ, respectively. Using the activated carbons, their adsorption characteristics for three target gases such as acetone, benzene, and methylmercaptan (MM) were carried out in a batch reactor. The adsorption behavior of activated carbons for three target gases followed the Freundlich model better than the Langmuir. And the experimental kinetic data followed a pseudo-second-order kinetic model more than pseudo-first-order one. Following the intraparticle diffusion model suggested that the external mass transfer and particle diffusion were occurred simultaneously during the adsorption process.

• Membrane and Water Treatment
• /
• v.14 no.4
• /
• pp.163-173
• /
• 2023

The presence of high amounts of organic and inorganic contaminants in textile wastewater is a major environmental concern. Therefore, the treatment of textile wastewater is an urgent issue to save the aquatic environment. The disposal of large quantities of untreated textile wastewater into inland water bodies can cause serious water pollution. In this study, synthetic dye wastewater samples were prepared using orange dye in the laboratory. The synthetic samples were then treated by a batch adsorption process using the prepared activated carbon (AC) from date pits. The wastewater parameters studied were the pH, total dissolved solids (TDS), total suspended solids (TSS), electrical conductivity (EC) and salinity. The activated adsorption process showed that the maximum removal efficiencies of electric conductivity (EC), salinity, TDS and TSS were 65%, 92%, 89% and 90%, respectively. The removal efficiencies were proportional to the increase in contact time (30-120 min) and AC adsorbent dose (1, 3 and 5 g/L). The adsorption profile indicates that 5 g/L of adsorbent delivers better results for TDS, EC, TSS and salinity at contact time of 120 min. The adsorption characteristics are better suited to the pseudo-second-order kinetic model than to the pseudo-first-order kinetic model. The Langmuir and Freundlich isotherms were well suited for describing the adsorption or contact behavior of EC and TSS within the studied system.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.4
• /
• pp.653-660
• /
• 2001

In this paper, we designed 2303.15MHz frequency synthesizer for the purpose of the phase noise prediction. For the modeling of phase noise generated in the designed system through introducing the noise-modeling method suggested by Lascari we analyzed a variation of phase noise as according as that of offset frequency. Especially, for the third-order system of the PLL among some kinds of phase noise generated from VCO we analyzed the aspect of 1/f-noise appearing troubles in the low frequency band. Since it is difficult to analyze mathematically 1/f-noise in the third-order system of the PLL, introducing the concept of pseudo-damping factor has made an ease of the access of the 1/f-noise variance. we showed a numerical formula of 1/f-noise variance in the third-order system of the PLL which is compared with that of 1/f-noise variance in the second-order system of the PLL. As a result, In case of txco we found the reduce rapidly along the offset frequency after passed through that phase-noise was -160dBc/Hz before passed through a loop at 10kHz offset frequency and -162.6705dBc/kHz after passed through the loop, -180dBc/Hz at 100kHz offset frequency and -560dBc/kHz after passed through the loop. We can notice that the variance of third-order system more occurs (or the variance of second-order system in connection with noise bandwidth and variance factor of second-order and third-order system.

• Environmental Engineering Research
• /
• v.21 no.4
• /
• pp.384-392
• /
• 2016

The aim of this study was to investigate the removal efficiency of $17{\alpha}$-methyltestosterone (MT) from aqueous solution by Salvinia cucullata Roxb. ex Bory in an active plant-based reactor with a specific focus on linear regression analysis for the sorption phenomena of MT onto the plant roots. A high performance liquid chromatographic method using UV detection (245 nm) was used to analyse the samples. The batch experiments of the active plant reactor (APR) were established to investigate the ability of Salvinia cucullata to remove MT from the liquid phase. The results revealed that 40% and 60% removal of MT from the liquid phase was observed at 5 min. and at 4 h, respectively. Salvinia cucullata can effectively remove MT from the aqueous solution in APRs. Kinetic studies revealed that the sorption phenomena of MT by Salvinia is best described using a linearized pseudo - second order model. Based on the kinetic parameters, it is likely that during the first 4 h of the contact (t = 0 to t = 4 h) sorption is the major driving mechanism of the disappearance of MT from aqueous solutions. However, at higher MT concentrations, diffusivity of MT has a significant effect on the migration of MT from the bulk stream to the root surface. The isotherm analysis revealed that the sorption kinetics favourably followed pseudo second-order. The results of isotherm analysis have indicated that the sorption of MT onto the root surfaces of Salvinia cucullata was favourable and almost irreversible.

• Journal of Environmental Science International
• /
• v.26 no.6
• /
• pp.719-728
• /
• 2017

In order to investigate the adsorption characteristics for Sr ion using the Na-X zeolite synthesized from coal fly ash, batch tests and response surface analyses were carried out. The adsorption kinetic data for Sr ions, using Na-X zeolite, fitted well with the pseudo-second-order model. The uptake of Sr ions followed the Langmuir isotherm model, with a maximum adsorption capacity of 196.46 mg/g. Thermodynamic studies were conducted at different reaction temperatures, with the results indicating that Sr ion adsorption by Na-X zeolite was an endothermic (${\Delta}H^o$>0) and spontaneous (${\Delta}G^o$<0) process. Using the response surface methodology of the Box-Behnken method, initial Sr ion concentration ($X_1$), initial temperature ($X_2$), and initial pH ($X_3$) were selected as the independent variables, while the adsorption of Sr ions by Na-X zeolite was selected as the dependent variable. The experimental data fitted well with a second-order polynomial equation by multiple regression analysis. The value of the determination coefficient ($R^2=0.9937$) and the adjusted determination coefficient (adjusted $R^2=0.9823$) was close to 1, indicating high significance of the model. Statistical results showed the order of Sr removal based on experimental factors to be initial pH > initial concentration > temperature.

• Environmental Engineering Research
• /
• v.13 no.2
• /
• pp.79-84
• /
• 2008

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.

• Advances in environmental research
• /
• v.5 no.1
• /
• pp.37-50
• /
• 2016

The main objective of this study is to evaluate adsorptive removal of Methylene Blue (MB) dye from aqueous solution using pumice powder. The effects of pH, adsorption time, agitation speed, adsorbent dose, and dye concentrations on dye adsorption were investigated. Process kinetics and isotherm model constants were determined accordingly. The results showed that adsorbent dose, dye concentration and agitation speed are the important parameters on dye adsorption and the removal of MB did not significantly change by varying pH. A total adsorption process time of 60 min was observed to be sufficient to effectively remove 50 mg/L MB concentration. The MB adsorption data obeyed both pseudo first order and second order kinetic models. Adsorption of MB by pumice fitted well both Langmiur and Freundlich isotherms ($R^2{\geq}0.9700$), except for 150 rpm agitation speed that system fitted only Langmiur isotherm. The results of this study emphasize that pumice powder can be used as a low cost and effective adsorbent for dye removal.

• Carbon letters
• /
• v.20
• /
• pp.10-18
• /
• 2016

Nanoporous carbon structures were synthesized by pyrolysis of grass as carbon precursor. The synthesized carbon has high surface area and pore volume. The carbon products were acid functionalized and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, transmission electron microscopy, and Energy Dispersive X-ray microanalysis. Acid functionalized nanoporous carbon was explored for use in removal of toxic Cr(VI) ions from aqueous media. An adsorption study was done as a function of initial concentration, pH, contact time, temperature, and interfering ions. The experimental equilibrium data fits well to Langmuir isotherm model with maximum monolayer adsorption capacity of 35.335 mg/g. The results indicated that removal obeys a pseudo-second-order kinetic model, and that equilibrium was reached in 10 min. A desorption study was done using NaOH. The results of the present study imply that acid functionalized nanoporous carbon synthesized from grass is an efficient, renewable, cost-effective adsorbent material for removal of hexavalent chromium due to its faster removal rate and reusability.

• Journal of Environmental Science International
• /
• v.24 no.11
• /
• pp.1331-1341
• /
• 2015

The removal of Sr ion and Cs ion was investigated to evaluate adsorption properties by using SAN-Zeolite beads immobilized with styrene acrylonitrile (SAN). The adsorption capacities increased with the decrease of SAN/zeolite ratio (SAR) from 2.5 to 0.83. The relationship of adsorption capacity ($q_e$) and SAR was described by experimental equation such as $q_e=20.88+137.81e^{-1.96SAR}$ ($r^2=0.9980$). The adsorption kinetics of Sr ion and Cs ion with SAN-Zeolite beads were fitted well by the pseudo-second-order model. The maximum adsorption capacities of Sr ion and Cs ion calculated from Langmuir isotherm model were 66.97 mg/g and 81.97 mg/g, respectively.