• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
• /
• pp.15-18
• /
• 2001

Sorption/desorption studies were conducted to determine sorption/desorption characteristics of phenolic compounds (phenol and 4-chlorophenol) in organically modified natural bentonite. The cationic exchange capacity (CEC) of bentonite was exchanged with a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the removal capacity of organic phenol contaminants dissolved in aqueous solution. This modification produces a change of the surface property of bentonite from hydrophilic to organophilic. The single-solute and bi-solute competitive adsorptions were performed In batch mode to investigate the removal of two toxic organic Phenols, chlorophenol and 4-chlorophenol on the HDTMA-bentonite. The adsorption affinity of the 4-chlorophenol was higher than phenol due to higher octanol:water partition coefficient (Kow). The single-solute and bi-solute competitive desorptions were also performed investigate the competitive desorption of the phenolic compounds from HDTMA-bentonite. Freundlich model was used to analyze the single-solute adsorption/desorption results, while the IAST model predicted the hi-solute adsorption/desorption equilibria. The IAST model well predicted hi-solute competitive adsorption/desorption behaviors.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2001년도 추계학술발표회
• /
• pp.19-22
• /
• 2001

The effects of pH on the sequential sorption/desorption of chlorinated phenols (2-chlorophenol, 2.4-dichlorophenol and 2,4,5-trichlorophenol) in HDTMA-montmorillonite were investigated by maintaining pH 4.85 or 9.15 in the sequential batch sorption and desorption experiments. The chlorinated phenols are hydrophobic ionizable orginic compounds; they can exist as either neutral (pH << pKa) or anionic (pH >> pKa) forms. Among the tested chlorinated phenols, 2,4,5-trichlorophenol showed the highest sorption affinity at pH 4.85 as expected by the $K_{ow}$ . Neutral speciation at pH 4.85 exhibited higher sorption affinity than anionic speciation at pH 9.15. Our results indicates that desorption of chlorinated phenols is strongly dependent on pH of the aqueous phase. Freundlich model was used to analyze the single-solute sorption/desorption results. The ideal adsorbed solution theory(IAST) was employed to predict the hi-solute sorption/desorption equilibria.

• 한국환경보건학회지
• /
• 제21권3호
• /
• pp.77-86
• /
• 1995

Lead(II) removal efficiency by natural kaolinite was investigated through laboratory experiments. This study was conducted in two phases-sorption and desorption. In the adsorption study, the influence of sorption kinetics and sorption isotherm and various parameters such as pH, temperature, coexisting other heavy metal ions on the lead adsorption was investigated. And desorption study was carried out in order to find the re-usability of kaolinite as an adsorbent. The results of the study are as follows. 1. Sorption kinetics was investigated under the condition of 2.5 mg/l adsorbent concentration, pH 6.5$\pm$0.05, temperature $30\pm 0.5\circ$C, initial lead(II) concentration 25 mg/l. Adsorption rate was initially rapid and the extent of adsorption arrived at adsorption equilibrium with 73% adsorption efficiency in an hour. 2. The sorption isotherm experiment was made with different initial lead(II) concentration. A linearized Freundlich equation was used to fit the acquired experimental data. As a result, Freundlich constants, the sorption intensity (1/n) was 0.47 and the measure of sorption (k) was 2.44. So, it was concluded that sorption of lead(II) by kaolinite is effective. 3. The effect of pH on lead(II) sorption by kaolinite shows that at a pH of 3, only 6% of the total lead(II) was adsorbed and at a pH 9, 97% of the lead(II) was removed. And the effect of temperature on lead(II) sorption by kaolinite shows that as the temperature increased, the amount of lead(II) sorption per unit weight of kaolinite increased. But the effect was minor (p<0.05). 4. Sorption isotherm of lead coexisting cadmium (II) or zinc (II) was lower than that of lead itself. It was caused by the result of competitive sorption to adsorption site. And there was no difference between the sorption isotherm of cadmium and zinc. 5. In desorption studies, only 5.12% desorption took place in distilled water, while 52.08% in 0.1 N hydrochloric acid. Consequently used kaolinite could be regenerated by hydrochoric acid.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2018년도 추계학술논문요약집
• /
• pp.253-254
• /
• 2018

• 한국토양비료학회지
• /
• 제49권5호
• /
• pp.541-547
• /
• 2016

In this experiment we investigated the influence of various anions including oxalic acid encountered as solution phase in soil on the adsorption and desorption of sulfate in Chungwon Bt soil. The effect of chloride and nitrate on the adsorption of sulfate was not significant, suggesting that sulfate was better able to compete for adsorption sites at concentrations studied, in contrast to the large reduction in the amount of chloride adsorbed in the presence of sulfate. The results of competition for sorption sites between sulfate and anion showed that the simultaneous presence of two anions in solution was effective in reduction of competing anion at a maximum value of adsorption, due to the similar adsorption mechanism for anion competition. Therefore, the variation in the buffer power of the acids will produce a change in the strength and amount of adsorption and the competitive ability.

• Korean Chemical Engineering Research
• /
• 제55권1호
• /
• pp.121-129
• /
• 2017

$TiO_2$, $Al_2O_3$, $ZrO_2$, $SiO_2$와 같은 다양한 담체에 습식함침법을 이용하여 Pd 기반 촉매를 제조하여 일산화탄소 존재하에 수소의 선택적 산화반응에 적용하였다. 제조된 촉매는 물리화학적 특성을 알아보기 위하여 XRD, $N_2$ 흡착, CO-, (CO+$H_2O$)-TPD, CO-TPR, XPS등의 특성분석을 수행하였다. CO-TPD와 (CO+$H_2O$)-TPD를 통해 $CO_2$ 탈착에 대한 $H_2O$의 영향을 알아보았으며 이러한 TPD 결과는 $H_2/CO$ 전환율과 상관관계가 있음을 확인하였다. 사용된 촉매 중에서 $Pd/ZrO_2$가 $H_2$ 전환율 측면에서 가장 활성이 좋은 것으로 나타났다. $H_2O$가 첨가된 선택적 $H_2$ 산화반응에서는 $H_2O$, CO, $H_2$가 경쟁흡착을 하였으며, 첨가된 $H_2O$가 CO 및 $H_2$의 반응을 촉진시켰다.

• 청정기술
• /
• 제17권1호
• /
• pp.41-47
• /
• 2011

순수한 $MnO_2$ 산화물을 과망간산칼륨과 망간아세테이트를 사용하여 침전법으로 제조하였고 소성온도를 달리하여 CO 산화반응을 수행하였다. 촉매의 물리화학적 특성을 알아보기 위하여 XRD, $N_2$ 흡착, $H_2-TPR$, CO-TPD 등의 특성분석을 수행하였다. $MnO_2$-300 촉매는 9nm 크기 근처의 좁은 기공크기 분포로 존재하며 $181m^2/g$의 높은 비표면적을 보였다. XRD와 $H_2-TPR$ 분석으로 $MnO_2$ 촉매는 $Mn^{4+}$와 $Mn^{3+}$의 산화상태임을 확인하였다. CO-TPD 분석으로 소성온도가 높아질수록 탈착되는 $CO_2$의 양이 감소하는 것을 확인하였다. $MnO_2$ 촉매의 소성온도에 따른 최적 활성에서는 $300^{\circ}C$에서 소성한 촉매가 가장 좋은 활성을 나타냈으며, $200^{\circ}C$ 이하에서 100%의 CO 전환율을 보였다. 수분 존재하의 CO 산화반응은 활성점에 $H_2O$와 CO의 경쟁 흡착으로 촉매의 활성을 감소시켰으며 수분제거 시 활성이 건조조건과 동일하게 회복되었다.

• 청정기술
• /
• 제16권2호
• /
• pp.132-139
• /
• 2010

서로 다른 몰비의 Cu-Mn 혼합산화물을 공침법으로 제조하여 $30^{\circ}C$에서 CO 산화반응을 수행하였다. 제조된 촉매는 CO 산화반응에서 반응 활성과 연관시키기 위하여 XRD, $N_2$ 흡착 및 탈착, XPS, $H_2-TPR$ 등의 특성분석을 수행하였다. 제조된 촉매의 질소흡착 등온곡선은 4형태로 7-20 nm크기의 세공이 존재하며, Mn의 함량이 증가함에 따라 BET 표면적은 17에서 $205m^2{\cdot}g^{-1}$ 으로 증가하였다. XPS 분석으로 Cu-Mn 혼합산화물 상의 Cu는 주성분이 2+의 산화상태임을 확인하였고, Mn은 +3과 +4의 산화 상태를 나타냈다. Cu-Mn 촉매의 함량 및 비율에 따른 최적 활성을 실험 조사한 결과, $30^{\circ}C$의 반응온도에서 Cu/(Cu+Mn)의 몰비가 0.5일 때 가장 좋은 활성을 나타냈으며, 이를 기준으로 화산형 형태의 반응 곡선을 나타냈다. 수분 존재하의 CO 산화반응은 활성점에 수분과 CO의 경쟁흡착으로 촉매의 활성을 감소시켰으며 최종적으로는 활성금속 성분과 하이드록실 그룹을 형성하였기 때문이다.