• Applied Biological Chemistry
• /
• v.41 no.2
• /
• pp.181-186
• /
• 1998

The effects of sewage treatment on characteristics of sludge as a composting material were investigated for a year during the initial operation at the full-scale Chunan sewage treatment plant. Due to the shortage of design capacity of belt press, a sludge dewatering unit, non-volatile solids were recirculating and concentrating in the treatment plant, resulting in an increase of MLSS and a decrease in F/M ratio at the activated sludge system. Special attention is required for long term operations since the increase of non-volatile solids in the plant would deteriorates the treatment efficiency. The sewage sludge of the Chunan sewage treatment plant showed 79.5% of water content, 11.6% of organic content, and C/N ratio of 6.1, and contained As 1.8 mg/kg, Cd 27 mg/kg, Hg <0.1 mg/kg, Pb 54 mg/kg, T-Cr 370 mg/kg, and Cu 1,100mg/kg of heavy metals. In order to be used as raw material for optimum composting, the sewage sludge requires bulking agents for moistrure/porosity control and a carbon source for adjusting C/N ratio. However, the sewage sludge is not adequate as a soil conditioner after composing due to a high content of heavy metals. If the sewage sludge has to he used as a soil conditioner after composting, it as required to identify and remove tire industrial wastewater portions in tire influent of the plant since heavy metals in the influent were mostly concentrated in dewatered sludge.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2009.11a
• /
• pp.19-20
• /
• 2009

최근 화학, 물리, 생명과학, 전기, 전자등의 다양한 분야에 활발하게 연구가 이루어지고 있는 초분자 화학은 선택적 분자인지를 위한 효율적인 골격구조와 나아가 다양한 계에 응용할 수 있다. 초분자 화학의 분자인지 과정의 특징은 일반적으로 수용체 (receptor 혹은 host)가 목표가 되는 기질 (substrate, analyte, 혹은 guest)에 대하여 선택적으로 식별하고 반응하는 것이다. 비공유 결합성 상호작용에 의하여 이루어지는 초분자 화학의 분자 인지 과정의 특징은 일반적으로 수용체 (receptor 혹은 host)가 목표가 되는 기질 (substrate, analyte, 혹은 guest)에 대하여 선택적으로 식별하고 반응하는 것이다. 이는 공유결합을 이용하는 분자화학과는 차별화 된 것이다. 수용체는 간단한 구조의 화합물 및 금속 이온들과 같은 기질과 가역적으로 상호 작용할 수 있는 착물을 형성한다. 최근들어 급격한 산업화가 진행되어 환경문제가 심각하게 대두 되어져 왔고, 그 중에서 특히 수은이나 카드뮴에 의한 질병, 납에 의한 중독 등 중금속에 의한 오염이 크게 나타남에도 불구하고, 현재 그러한 중금속을 검출함에 있어 많은 비용과 시간이 드는 문제점이 있다. 또한 우리에게 이로운 금속은 효율적 분석을 통해 환경계와 의료계에 많은 도움을 줄 것으로 사례되므로 화학센서 기술의 개발은 절실히 요구되어지고 있다. 이에 새로운 1,3-bisdicyanovinylindane 을 통해 $Hg^{2+}$ 금속의 감지 여부 알아보고, 그 특성을 파악하고자 한다. 1,3-indandion (2.18g, 14.9mmol), malononitrile (2.95g, 44.7mmol), ethanol 50ml를 20분간 상온에서 용해시킨다. 후에 sodium trihydrate acetate(3.05g)을 첨가한 후 5시간 동안 환류반응 시킨다. 이 과정에서 얻어진 용액을 필터과정을 통하여 에서 합성 반응 중에 생성된 불순물(1,3-dicyanovinylindane-1-one, monocondensation)을 제거한다. 필터과정을 통해 걸러진 미 반응 물질을 제�G 용반응욕액을 증류수(100ml)를 이용하여 희석시키고 난 후 염산을 이용, 산성화 시켜 고체 생성물을 얻어낸다. 이렇게 생성된 고체 생성물은 다시 필터 및 건조를 통하여 회색의 고체 화합물을 얻어낸다. 1,3-bisdicyanovinylindane과 금속이온에 대한 감응도를 확인하기 위하여 metanol/water(1:2)을 용매로 하여 금속이온의 농도를 변화시켜 발색특성을 살펴보았다. 본 색소화합물과 Hg2+에 대한 UV 흡광도 변화 적정결과와 그 화합물의 상태 살펴본 결과 금속이온이 0.2ml씩 더 참가되면서 색의 변화를 뚜렷하게 나타내었다. 반면 그 밖에 이온($Fe^{3+}$, $Ag^{2+}$, $Pd^{2+}$, $Zn^2$, $Fe^{2+}$, $Cu^{2+}$, $Pb^{2+}$)은 UV 흡광도 변화가 적거나 변화 자체가 없었다. 하지만 과량의 $Fe^{3+}$, $Ag^{2+}$, $Pd^{2+}$는 색상 변화를 나타내었으며,이와 같은 흡광도 변화는 금속에 따라 약간의 차이가 있지만, 420nm를 등흡수점으로 하여, 580nm의 파장 영역에 있는 흡수 밴드의 세기는 감소하는 반면 400nm 파장 영역에 있는 흡수 밴드의 세기가 증가하였다. 1,3-bisdicyanovinylindane 화합물은 다양한 생물계 및 환경계에서 요구되는 micro mol에서 milli mol 농도 영역의 $Hg^{2+}$ 이온의 선택적이고 민감한 검출과 정량적인 분석에 유용하게 사용될 수 있을 것이다.

• Applied Chemistry for Engineering
• /
• v.24 no.1
• /
• pp.67-71
• /
• 2013

$FeCl_3$ has been used as an etchant for metal etching such as Fe, Cu, and Al. In the process of metal etching, $Fe^{3+}$ is reducted to $Fe^{2+}$ and the etching rate becomes slow and etching efficiency decreased. Waste $FeCl_3$ etchant needs to be regenerated because of its toxicity and treatment cost. In this work, HCl was initially mixed with the waste $FeCl_3$ and then, strong oxidants, such as $O_2$ and $H_2O_2$, were added into the mixed solution to regenerate the waste etchant. During successive etching and regeneration processes, oxygen-reduction potential (ORP) was continuously measured and the relationship between ORP and etching capability was investigated. Regenerated etchant using a two vol% HCl of the total etchant volume and a very small amount of $H_2O_2$ was very effective in recovering etching capability. During the etching-regeneration process, the same oxygen-reduction potential variation cannot be repeated every cycle since concentrations of $Fe^{2+}$ and $Fe^{3+}$ ions were continuously changed. It suggested that the control of etching-regeneration process based on the etching time becomes more efficient than that of the process based on oxygen reduction potential changes.

• Membrane Journal
• /
• v.21 no.1
• /
• pp.22-29
• /
• 2011

During the maintenance, repair and replacement process of circuit breaker, $SF_6$ reacted with input air in arc discharge, which led to the production of by-product gases (eg, $N_2$, $O_2$, $CF_4$, $SO_2$, $H_2O$, HF, $SOF_2$, $CuF_2$, $WO_3$). Among these various by-product gases, $N_2$, $O_2$, $CF_4$ is major component. Therefore, the effective separation process is necessary to recycle the $SF_6$ gas from the mixture gas containing $N_2$, $O_2$, $CF_4$. In this study, the membrane separation process was applied to recycle the $SF_6$ gas from the mixture gas containing $N_2$, $O_2$, $CF_4$. The concentration of $SF_6$ gas in gas produced from the electric power industry is over than 90 vol%. Therefore, we made the simulated gas containing $N_2$, $O_2$, $CF_4$, $SF_6$ which the concentration of $SF_6$ gas is minimum 90 vol%. From the results of membrane separation process of $SF_6$ gas from $N_2$, $O_2$, $CF_4$ $SF_6$ mixture gases, PSF membrane shown the highest recovery efficiency 92.7%, in $25^{\circ}C$ and 150 cc/min of retentate flow rate. On the other hand, PC membrane shown the highest recovery efficiency 74.8%, in $45^{\circ}C$ and 150 cc/min of retentate flow rate. Also, the highest rejection rate of $N_2$, $O_2$, $CF_4$ is 80, 74 and 58.9% seperately in the same operation condition of highest recovery efficiency. From the results, we supposed the membrane separation process as the effective $SF_6$ separation and recycle process from the mixture gas containing $N_2$, $O_2$, $CF_4$, $SF_6$.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.28 no.3
• /
• pp.15-26
• /
• 2020

To recover phosphorus from incinerated sewage sludge ash(ISSA), ISSA were extracted with sulfuric acid solution, and the optimal phosphorus recovery conditions were experimented by comparing the recovered phosphorus contents and heavy metals by raising pH. Also the phosphorus recovery efficiency was compared when acid extract was reused or classified by particle size of ISSA. The optimal conditions for recovering phosphorus from ISSA were 1N sulfuric acid solution with an L/S ratio of 10, and an extraction time of 30 minutes. Considering the addition of alkali substances and the content of heavy metals in the recovered sediment, it is concluded to recover phosphorus under pH 5. Reuse of the ISSA extract increased the recovery rate of phosphorus by 14~21% depending on the reuse rate (100 and 50%), but it also increased zinc contents to 33 and 21%, and copper contents to 35 and 20%, respectively. The experiment of ISSA divided into four sections by particle size showed that there was no distinct advantage of phosphorous recovery by classification of certain particle size of ISSA. The removal of heavy metals from extracts through EDTA and cation exchange resin showed no definite effect.

• Resources Recycling
• /
• v.25 no.2
• /
• pp.33-41
• /
• 2016

A scale up tests (380 kg/day) using a continuous solvent extraction and electro-winning system was carried out to separate and recover cobalt from a solution containing 1.91 g/L Co and 14.65 g/L Ni. The solution was obtained during a process including solvent extraction and precipitation stages for removal of Cu and Fe from a synthetic sulfuric acid solution of manganese nodule matte. The optimal condition for solvent extraction was : solvent concentration of 0.22M Na-Cyanex 272 (45% saponified with NaOH) and O:A phase ratios of 1:1.5, 10:1 and 1.5:1 used in extraction, scrubbing and stripping stages, respectively. The extraction and stripping efficiencies were found to be 99.8% and 99.88%, respectively. The stripped solution contained 40.27 g/L Co with 4 ppm Ni. Cobalt metal of 99.963% purity was yielded with current efficiency of 67% and current density of $0.563A/dm^2$ during the electro-winning process.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.3
• /
• pp.314-322
• /
• 2008

This study was carried out to assess aerobic stabilized waste sludge as liquid fertilizer for the growth of cucumber, cabbage and chrysanthemum. Sludge was pretreated with NaOH(40 meq/L) at 40$^{\circ}C$ for 330 min. The number of fecal coliforms in batch test sludge fertilizer was more efficiently reduced than those in continuous one, maybe due to longer SRT. All produced fertilizer belonged to class B according to US EPA requirement at least. Among 6 heavy metals regulated in Korea, As, Cd and Hg were not detectable in plant amended with fertilizer whereas the concentration of Cr, Cu and Pb in plant was less than 10 mg/kg dw. However, Zn and Ni, which were restricted in other country, but not in Korea, were detected in most amount of 118 mg/kg and 15.7 mg/kg, respectively. Furthermore, based on dry weight of plant, digested sludge(5.4 mg, dw) functioned as better fertilizer rather than activated sludge (4.3 mg, dw), much more fertile when those sludge was pretreated(1.24 mg, dw) compared to untreated one(1.12 mg, dw). But its fertility was 60$\sim$80% of commercial fertilizer and accumulation of Zn, Ti and Cr in plant was founded. Therefore, it could be concluded that sludge-fertilizer can be used for flower unlimitedly, but for edible plant limitedly as additive fertilizer.