• 공업화학
• /
• 제31권5호
• /
• pp.495-501
• /
• 2020

In this study, zirconium fumarate of metal-organic framework (MOF-801) was solvothermally synthesized at 130 ℃ and characterized through powder X-ray diffraction (PXRD) analyses and porosity measurements from N₂ sorption isotherms at 77 K. The ability of MOF-801 to act as an adsorbent for the phosphate removal from aqueous solutions at 25 ℃ was investigated. The phosphate removal efficiency (PRE) obtained by 0.05 g/L adsorbent dose at an initial phosphate concentration of 60 ppm after 3 h was 72.47%, whereas at 5 and 20 ppm, the PRE was determined to be 100% and 89.88%, respectively, after 30 min for the same adsorbent dose. Brunauer-Emmett-Teller (BET) surface area and pore volume of the bare MOF-801 sample were 478.25 ㎡/g and 0.52 ㎤/g, respectively, whereas after phosphate adsorption (at an initial concentration of 60 ppm, 3 h), the BET surface area and pore volume were reduced to 331.66 ㎡/g and 0.39 ㎤/g, respectively. The experimental data of kinetic (measured at initial concentrations of 5, 20 and 60 ppm) and isotherm measurements followed the pseudo-second-order kinetic equation and the Freundlich isotherm model, respectively. This study demonstrates that MOF-801 is a promising material for the removal of phosphate from aqueous solutions.

• Food Science and Biotechnology
• /
• 제16권1호
• /
• pp.154-158
• /
• 2007

Adsorption isotherms for chaga mushroom powder as influenced by particle size were investigated using a gravimetric technique. Samples were equilibrated in desiccators containing sulfuric acid solutions of known water activity (0.11-0.93), then placed in temperature-controlled chambers for approximately ten days. Equilibrium moisture content (EMC) of chaga mushroom powder increased with water activity in all samples. EMC was slightly greater in the samples comprised of smaller particle size, however there was no marked difference in appearance between the three samples. The chaga mushroom powder exhibited Type II behavior. When the BET model was used to determine mean monolayer values, 0.077, 0.077, and 0.070 $H_2O/dry$ solid was observed for <250, 250-425, and $425-850\;{\mu}m$ sized samples, respectively, however mean monolayer values were 0.121, 0.111, and 0.101 $H_2O/dry$ solid, respectively, when the GAB model was used. The experimental EMC values were related to the computed values from Henderson's model. The coefficient of determination and standard error for the linear regression were 0.997 and 0.003, respectively.

• 공업화학
• /
• 제30권3호
• /
• pp.316-323
• /
• 2019

The adsorption of bisphenol A from an aqueous solution onto dried rice husk was investigated. Batch adsorption experiments were performed as a function of the pH, contact time, bisphenol A concentration, adsorbent dose and temperature. The concentration of Bisphenol A was measured by HPLC. The results showed that bisphenol A removal was highest at a solution pH value of 3, adsorbent dose of 4 g/L, and contact time of 75 min. The bisphenol A removal percentage decreased from 99.1 to 66.7%, when the bisphenol A concentration increased from 10 to 200 mg/L. The Langmuir isotherm and pseudo-second order kinetics provided the best fit for the experimental data. Thermodynamic parameters such as ${\Delta}G^0$, ${\Delta}H^0$ and ${\Delta}S^0$ were also evaluated and it was found that the sorption process was feasible, spontaneous and exothermic in nature. Overall, the studied absorbent can be used as an effective and low cost material to treat the industrial wastewater and aqueous solution containing phenolic compounds.

• 한국환경농학회지
• /
• 제40권1호
• /
• pp.40-48
• /
• 2021

BACKGROUND: Although the calcined oyster shell can be used as a calcium-rich adsorbent for phosphate removal, information about it is limited. The purpose of this study was to evaluate the phosphate adsorption characteristics and its mechanism using calcined oyster shells. METHODS AND RESULTS: In this study, calcined oyster shell (C-OS600) was prepared by calcining oyster shells (P-OS) at 600℃ for 20 min. Phosphate adsorption by C-OS600 was performed under various environmental conditions. Phosphate adsorption by C-OS600 occurred rapidly at the beginning of the reaction, and the time to reach equilibrium was less than 1 h. The optimal isotherm and kinetic models for predicting the adsorption of phosphate by C-OS600 were the Langmuir isotherm and pseudo-second order kinetic model, respectively, and the maximum adsorption capacity derived from the Langmuir isotherm was 68.0 mg/g. The adsorption properties of phosphate by C-OS600 were dominantly influenced by the initial pH and C-OS600 dose. In addition, SEM-EDS and FTIR analysis clearly showed a difference in C-OS600 before and after phosphate adsorption, which proved that phosphate was adsorbed on the surface of C-OS600. CONCLUSION: Overall, the calcined oyster shell can be considered as an useful and effective adsorbent to treat wastewater containing phosphate.

• 한국식품저장유통학회지
• /
• 제21권3호
• /
• pp.334-340
• /
• 2014

볶음온도에 따른 옥수수 분말의 흡습특성을 구명하기 위하여, 옥수수 낟알을 160, 180, 200, 220, $240^{\circ}C$에서 20분간 볶은 후 분쇄하고, $20^{\circ}C$에서 각 분말의 수분활성도($a_w$) 0.11, 0.33, 0.53, 0.75, 0.90에 따른 평형수분함량(EMC)을 측정하여 등온흡습곡선을 작성하였다. 볶은 옥수수 분말의 등온흡습곡선은 $a_w$ 증가에 따른 EMC 증가가 전형적인 sigmoid 형태를 보였으며, $a_w$ 0.53 이상의 영역에서는 동일 $a_w$에서 볶음온도가 고온일수록 높은 EMC를 나타내었다. 옥수수 분말의 등온흡습곡선은 볶음온도의 뚜렷한 영향이 없이 Oswin, Caurie, Henderson, Halsey 모델로 설명이 가능하였으며, 가장 적합한 모델은 Oswin인 것으로 나타났다. 단분자층 수분함량은 전범위의 $a_w$영역에서 GAB 방정식으로 예측할 수 있었으며, 볶음온도가 높아짐에 따라 증가하는 경향을 보여서 $180^{\circ}C$에서는 0.043 kg $H_2O/kg$ solids, $240^{\circ}C$에서는 0.053 kg $H_2O/kg$ solids을 각각 나타내었다. 이로써 옥수수의 볶음온도가 분말의 $20^{\circ}C$ 흡습특성에 영향을 미치는 것으로 확인되었다.

• Environmental Engineering Research
• /
• 제14권3호
• /
• pp.164-169
• /
• 2009

A powder form of aluminum (hydr)oxides is not suitable in wastewater treatment/filtration systems because of low hydraulic conductivity and large sludge production. In this study, aluminum (hydr)oxide-coated sand (AOCS) was used to remove phosphate from aqueous solution. The properties of AOCS were analyzed using a scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectrometer (EDS) and an X-ray diffractometer (XRD). Kinetic batch, equilibrium batch, and closed-loop column experiments were performed to examine the adsorption of phosphate to AOCS. The XRD pattern indicated that the powder form of aluminum (hydr)oxides coated on AOCS was similar to a low crystalline boehmite. Kinetic batch experiments demonstrated that P adsorption to AOCS reached equilibrium after 24 h of reaction time. The kinetic sorption data were described well by the pseudo second-order kinetic sorption model, which determined the amount of P adsorbed at equilibrium ($q_e$ = 0.118 mg/g) and the pseudo second-order velocity constant (k = 0.0036 g/mg/h) at initial P concentration of 25 mg/L. The equilibrium batch data were fitted well to the Freundlich isotherm model, which quantified the distribution coefficient ($K_F$ = 0.083 L/g), and the Freundlich constant (1/n = 0.339). The closed-loop column experiments showed that the phosphate removal percent decreased from 89.1 to 41.9% with increasing initial pH from 4.82 to 9.53. The adsorption capacity determined from the closed-loop experiment was 0.239 mg/g at initial pH 7.0, which is about two times greater than that ($q_e$ = 0.118 mg/g) from the kinetic batch experiment at the same condition.

• Environmental Engineering Research
• /
• 제21권2호
• /
• pp.152-163
• /
• 2016

Present study investigates the potential of cassava peel and rubber tree bark for the removal of Cr (VI) from aqueous solution. Removal efficiency of more than 99% was obtained during the kinetic adsorption experiments with dosage of 3.5 g/L for cassava peel and 8 g/L for rubber tree bark. By comparing popular isotherm models and kinetic models for evaluating the kinetics of mass transfer, it was observed that Redlich-Peterson model and Langmuir model fitted well ($R^2$ > 0.99) resulting in maximum adsorption capacity as 79.37 mg/g and 43.86 mg/g for cassava peel and rubber tree bark respectively. Validation of pseudo-second order model and Elovich model indicated the possibility of chemisorption being the rate limiting step. The multi-linearity in the diffusion model was further addressed using multi-sites models (two-site series interface (TSSI) and two-site parallel interface (TSPI) models). Considering the influence of interface properties on the kinetic nature of sorption, TSSI model resulted in low mass transfer rate (5% for cassava peel and 10% for rubber tree bark) compared to TSPI model. The study highlights the employability of two-site sorption model for simultaneous representation of different stages of kinetic sorption for finding the rate-limiting process, compared to the separate equilibrium and kinetic modeling attempts.

• Advances in environmental research
• /
• 제8권1호
• /
• pp.23-38
• /
• 2019

In this study, Malachite Green (MG) dye removal from synthetic wastewaters by adsorption process using raw boron enrichment waste (BEW) and it's modifications (with acid and ultrasound) were aimed. 81% MG removal was obtained by BEW at optimum equilibrium conditions (time: 40 min., dosage: 500 mg/dm³, pH: 5-6, speed: 200 rpm, 298 K). MG removal from wastewaters using acid modified boron enrichment waste (HBEW) was determined as 82% at optimum conditions (time: 20 min., dosage: 200 mg/dm³, pH: 10, speed: 200 rpm, 298 K). For ultrasound modified BEW (UBEW), the highest MG removal percent was achieved as 84% at optimum conditions (time: 30 min, dosage: 375 mg/ dm³, pH: 8, speed: 200 rpm, 298 K). The equilibrium data of Malachite Green was evaluated for BEW, HBEW and UBEW adsorbents by using sorption isotherms such as Langmuir, Freundlich and Temkin models, out of which Langmuir model (R² = 0.971, 0.987 and 0.984) gave better correlation and maximum adsorption capacity was found to be 147.05, 434.78 and 192.30 mg/g, respectively. The adsorption kinetics followed the pseudo-second-order kinetic equation for sorption of MG onto wastes. A look at thermodynamic data reveals that natural sorption is spontaneous and endothermic because of free negative energy exchange and positive change in enthalpy, respectively. The results indicated that boron enrichment waste, and HCl and ultrasound-modified boron enrichment waste served as good alternative adsorbents in dye removal from wastewater.

• 한국재료학회지
• /
• 제27권3호
• /
• pp.166-171
• /
• 2017

Removal of phosphate from environmental water has become more important to prevent eutrophication. In the present study, sorption behavior of phosphate onto magnesite was investigated under different conditions. The optimum pH of phosphate adsorption was determined to be 6.0. The adsorption capacity was found to decrease with increasing temperature, which indicates that a low temperature was beneficial for phosphate adsorption. The sorption capacity for phosphate was found to be 10.2 mg/g at an initial concentration of 100 mg/L and a dose of 2 g/L. The first order kinetic equation and Freundlich isotherm model fit the data well. Phosphate adsorption on magnesite was explained by electrostatic attraction and weak physical interactions.

• 산업기술연구
• /
• 제27권A호
• /
• pp.195-202
• /
• 2007

Milled Korean pine (Pinus densiflora) wood was used to evaluate its adsorption capacity of Cu(II) ions from aqueous solution by running a series of batch experiments. Prior to the tests, the milled woods were pretreated with 1N NaOH, 1N $HNO_3$, and distilled water, respectively, to examine the effect of pretreatment. Within the tested pH range between 3 and 6, copper adsorption efficiency of NaOH-treated wood(96~99%) was superior to the $HNO_3$-treated wood(19~31%) and distilled water-treated wood(18~35%). The efficiency of copper removal by wood enhanced with increasing solution pH and reached a maximum copper ion uptake at pH 5~6. Adsorption behavior of copper onto both raw and $HNO_3$-treated woods was mainly attributed to interaction with carboxylic acid group. For NaOH-treated wood, carboxylate ion produced by hydrolysis or saponification was a major functional group responsible for Cu sorption. NaOH treatment of wood changed the ester and carboxylic acid groups into carboxylate group, whereas $HNO_3$ treatment did not affect the production of functional groups which could bind copper. A pseudo second-order kinetic model fitted well for the sorption of copper ion onto NaOH-treated wood. A batch isotherm test using NaOH-treated wood showed that equilibrium sorption data were better represented by the Langmuir model than the Freundlich model.