• 청정기술
• /
• 제16권3호
• /
• pp.162-171
• /
• 2010

본 연구에서는 유기산, 무기산, 여러 첨가제들을 이용하여 옥내급수관의 스케일 제거에 적합한 환경친화적인 세정제를 개발하고자 연구를 수행하였다. 여러 유기산 중에서 oxalic acid, citric acid, malic acid 등의 경우 산화철 제거에 비교적 좋은 효율을 보였다. 이들 유기산들을 주축으로 하여 보조제를 첨가하여 옥내급수관 스케일의 주성분인 산화철 제거 평가실험을 하였다. 여러 첨가제 중에 비이온 계면활성제가 산화철 제거력 향상에 매우 뛰어남을 확인할 수 있었다. 그리고 산화철에 대해 높은 용해력을 보인 두 종류의 배합세정제 $F_1$과 $F_2$를 제조하였는데 배합세정제 $F_1$의 경우 유기산과 첨가제로만 이루어져 있어 기존의 화학세척제에 비하여 안전하고 환경친화적이지만 비교적 산화철 용해력이 조금 떨어졌고, $F_2$의 경우는 $F_1$에 무기산을 소량 첨가함으로 산화철 용해력을 보완해 줌으로써 보다 높은 산화철 세정력을 필요로 할 때 사용하는 것이 좋을 것으로 판단된다. 따라서 옥내급수관 세정 시 스케일의 정도에 따라 배합후보 세정제를 선택하는 것이 바람직하다고 판단된다.

• Membrane and Water Treatment
• /
• 제12권1호
• /
• pp.1-9
• /
• 2021

This study optimized the chemical cleaning process of discarded RO membranes for reuse in less demanding separation processes. The effect of physicochemical parameters, including the temperature, cleaning time, pH of the cleaning solution, and addition of additives, on the cleaning process was investigated. The membrane performance was evaluated by testing the flux recovery rate and salt rejection before and after the cleaning process. High temperatures (45-50 ℃) resulted in a better flux recovery rate of 71% with more than 80% salt rejection. Equal time for acid and base cleaning 3-3 h presented a 72.43% flux recovery rate with salt rejection above 85%. During acid and base cleaning, the best results were achieved at pH values of 3.0 and 12.0, respectively. Moreover, 0.05% concentration of ethylenediaminetetraacetic acid presented 72.3% flux recovery, while 69.2% flux was achieved using sodium dodecyl sulfate with a concentration of 0.5%; both showed >80% salt rejection, indicating no damage to the active layer of the membrane. Conversely, 0.5% concentration of sodium percarbonate showed 83.1% flux recovery and 0.005% concentration of sodium hypochlorite presented 85.2% flux recovery, while a high concentration of these chemicals resulted in oxidation of the membrane that caused a reduction in salt rejection.

• 한국재료학회지
• /
• 제28권8호
• /
• pp.440-444
• /
• 2018

An effective cleaning method for Ni removal in Ni-induced lateral crystallization(Ni-MILC) poly-Si TFTs and their electrical properties are investigated. The HCN cleaning method is effective for removal of Ni on the crystallized Si surface, while the nitric acid treatment results decrease by almost two orders of magnitude in the Ni concentration due to effective removal of diffused Ni mainly in the poly-Si grain boundary regions. Using the HCN cleaning method after the nitric acid treatment, re-adsorbed Ni on the Si surfaces is effectively removed by the formation of Ni-cyanide complexions. After the cleaning process, important electrical properties are improved, e.g., the leakage current density from $9.43{\times}10^{-12}$ to $3.43{\times}10^{-12}$ A and the subthreshold swing values from 1.37 to 0.67 mV/dec.

• 한국재료학회지
• /
• 제16권2호
• /
• pp.80-84
• /
• 2006

The removal efficiency of Cu and Fe contaminants on the silicon wafer surface was examined to investigate the effect of cleaning solutions on the behavior of metallic impurities. Silicon wafers were intentionally contaminated with Cu and Fe solutions by spin coating and cleaned in different types of cleaning solutions based on $NH_4OH/H_2O_2/H_2O\;(SC1),\;H_2O_2/HCl/H_2O$ (SC2), and/or HCl/$H_2O$ (m-SC2) mixtures. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). Cu ions were effectively removed both in alkali (SC1) and in acid (SC2) based solutions. When $H_2O_2$ was not added to SC2 solution like m-SC2, the removal efficiency of Cu impurities was decreased drastically. The efficiency of Cu ions in SC1 was not changed by increasing cleaning temperature. Fe ions were soluble only in acid solution like SC2 or m-SC2 solution. The removal efficiencies of Fe ions in acid solutions were enhanced by increasing cleaning temperature. It is found that the behavior of metallic contaminants as Cu and Fe from silicon surfaces in cleaning solutions could be explained in terms of Pourbaix diagram.

• 한국표면공학회지
• /
• 제28권1호
• /
• pp.23-33
• /
• 1995

AISI 304 stainless steel has high resistance to corrosion due to the presence of a self-healing chromium oxide film on the surface, which also accounts for the difficulty in plating. Surface cleaning of this alloy is of fundamental importance in gold plating since its effectiveness puts an upper limit on the quality of the final coating. The cleaning of AISI 304 stainless steel was investigated with elimination of artificial passive oxide film and degreasing of remaining buffing wax as stearic acid. The familiar cleaning methods i.e. ultrasonic cleaning, electro-cleaning and activation treatment were fabricated in this study. Activation treatment showed best cleaning efficiency for elimination of passive oxide film among these methods, which was also confirmed by AES (Auger electron spectrometer) analysis. However, the best condition of cleaning was obtained by combining these methods. Electrocleaning time, for degreasing the stearic acid layer, was decreased with increasing amount of added KCN.

• 한국응용과학기술학회지
• /
• 제21권4호
• /
• pp.306-312
• /
• 2004

An acid cleaning agent (AACA) for aluminum was prepared by blending of sorbitol, n-octanoic acid, MJU-100A, Tetronix T-701, PPA-23, C8-83 and phosphoric acid. With the prepared AACA, degreasing, foam height, etching and derusting tests were carried out. As a result, AACA-4 and AACA-7 showed better cleaning ability than commercial acid cleaning agents.

• 청정기술
• /
• 제18권3호
• /
• pp.272-279
• /
• 2012

본 연구에서는 유기산과 여러 첨가제들을 사용하여 상수도의 정수장이나 배수지 벽면에 침적되어 있는 스케일 제거에 활용할 수 있는 친환경적인 세정제를 개발하고 현장 적용을 수행하였다. 정수장의 벽면의 스케일 분석결과 산화규소($SiO_2$), 산화알루미늄($Al_2O_3$), 산화철($Fe_2O_3$), 산화망간(MnO) 등 주로 금속산화물로 이루어져 있는 것을 알 수 있었다. 그리고 여러 유기산 중에서 말릭산(malic acid), 말론산(malonic acid), 시트릭산(citric acid)과 산화규소를 제외한 산화알루미늄, 산화철, 산화망간 등의 금속산화물에 비교적 좋은 용해력을 보여주었다. 이들 유기산들을 일정 무게비율로 배합하여 산화알루미늄, 산화철, 산화망간의 혼합 금속산화물의 용해력 실험 결과 여러 유기산 배합 비율 중 말릭산, 말론산, 시트릭산이 6 : 2 : 2 배합비율로 만든 10 wt% 유기산 혼합용액이 정수장 및 배수지의 스케일 제거효율이 약 29%로 가장 뛰어났음을 확인할 수 있었다. 이들 유기산 혼합용액에 비이온 계면활성제를 첨가하여 배합한 세정제 용액이 유기산 혼합용액만을 사용한 경우보다 더욱 높은 금속산화물 용해력을 가지는 것을 확인 할 수 있었다. 특히, 알콜에톡실레이트 계열의 LA-7 비이온계면활성제를 0.2% 첨가하는 경우 약 35%의 스케일 제거효율을 보여주었다. 그렇지만 유기산 혼합용액에 살균제를 첨가하는 경우 스케일 제거효율이 저하되었다. 이것은 계면활성제가 오염물의 유화분산 성질에 의해 스케일 제거력 향상에 도움을 주지만 살균제의 경우에는 살균제의 산화력에 의하여 스케일의 물에 대한 용해력을 떨어뜨려 스케일 제거에 방해를 하기 때문인 것으로 판단된다. 이러한 기초실험 결과를 바탕으로 유기산 혼합용액에 첨가제인 계면활성제, 살균제 등을 넣고 배합된 세정제를 사용하여 D시의 상수도 정수장 및 배수지의 스케일 세척시험에 성공적으로 적용시킬 수 있었다.

• Membrane and Water Treatment
• /
• 제10권4호
• /
• pp.277-286
• /
• 2019

In 2014, the first demineralization plant, using nanofiltration (NF) membrane coupled with renewable energies was realized at Al Annouar high school of Sidi Taibi, Kenitra, Morocco. This project has revealed difficulties related to the membrane performances loss (pressure increase, flux decline, poor water quality of the produced water and increase of energy consumption), as consequences of membrane fouling. To solve this problem, an autopsy of the membrane was done in order to determine the nature and origin of the fouling. The samples of membrane and fouling were then analyzed by scanning electron microscopy using a scanning electron microscope (SEM) connected with an energy dispersive X-ray (EDX) detection system and X-ray diffractometer (XRD). Moreover, three cleaning solutions (hydrochloric acid, nitric acid and sulfuric acid) were tested and assessed in a single cleaning step to find the suitable one for the fouled membrane to regain its initial permeability and performances. The analysis of the experimental results showed that the fouling layer is mainly composed of calcium carbonate (inorganic fouling). Results showed also that the permeability is improved by the hydrochloric acid cleaning (pH=3) with a cleaning efficiency of 93%. Cleaning efficiency did not exceed 75 % with nitric acid (pH=3) and 40 % with sulfuric acid (pH=3).

• 한국동물위생학회지
• /
• 제36권4호
• /
• pp.273-281
• /
• 2013

This study investigated the effects of the alkaline detergent and acid rinse used for cleaning milking machines on the eight commercially available teatcup liner materials. The sample liners prepared for use in the clean-in-place process were analyzed by ultraviolet spectrophotometer, ion chromatography and liquid chromatography. Among the eight liner materials, the ultraviolet spectra of 3 sample liners were shown to have a similar peak shape after cleaning, but the ultraviolet spectra peak shape of 5 sample liners was noticeably changed. No products were detected by ion chromatography in any of the liner materials used in this study. When the liner materials were only treated with alkaline detergent, some additional peaks were observed using liquid chromatography which indicate the creation of molecular substance and elution from liner materials, however, these peaks disappeared when the liner materials were cleaned with the acid rinse. Therefore, we propose that an acid rinse should be applied, after cleaning the milking machine with the alkaline detergent.

• Membrane and Water Treatment
• /
• 제6권2호
• /
• pp.141-160
• /
• 2015

This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3 and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron and sodium rejections are irreversible in most cases.