• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.257-262
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• 2013

The fluorine-containing waste water tends to show a higher removal efficiency through the coagulative precipitation process with calcium. However the tetrafluoroborate produced from the etching process is difficult to remaval due to it's low reactivity with calcium. The objective of this study is improving the efficiency of fluoride ion removal in tetrafluoroborate through decomposing. Research on tetrafluoroborate decomposition depending on reaction pH, temperature, and aluminum dosage were conducted, using a laboratory-scale reactor. The result shows that the reaction of tetrafluoroborate with aluminum is faster with lower pH, higher water temperature, and higher Al/T-F (Aluminum/Total Fluoride) mole ratio. It is found that there was no big change in concentration after over 120 minutes of reaction. This study is to be able to improve the efficiency of tetrafluoroborate and fluoride wastewater treatment by using aluminum.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.469-473
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• 2017

In this study, the rheological characteristics of kerosene based gel propellants were investigated. For the gelling agent, Thixatrol$^{(R)}$ has been used with 100 nm nano-sized aluminium particle addition. Three gellant contents of 2.5 wt%, 5 wt% and 7.5 wt% kerosene gels were first investigated where aluminium particles contents of 10 wt% and 20 wt% were added to 7.5 wt% gellant case. The viscosities of each sample measured by rotational rheometer show that the viscosity augments as gellant or aluminium content increases while the 20 wt% aluminum content resulted in failure of measurement due to the agglomerations of aluminum particles.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.205-211
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• 2010

The water-sewage cohesion agent(polyaluminumchloride(PAC)) and NaOH were used to synthesize $Al(OH)_3$. For various additions of NaOH, characteristics of the synthesized $Al(OH)_3$ was analysed by XRD, SEM and PSA. According to XRD analysis, small amount of NaOH(NaOH:PAC=15g:100g) resulted in amorphous form of $Al(OH)_3$. By increasing NaOH(NaOH:PAC=20g:100g), the mixture of gibbsite(37%), bayerite(35%) and boehmite(28%) were produced. By adding more NaOH(NaOH:PAC=25g:100g), binary mixtures of gibbsite(67%) and bayerite(33%) were formed. Finally, high addition of NaOH(NaOH:PAC=30g:100g) gave the high concentration of gibbsite(gibbsite:bayerite=83:17). Also, SEM analysis indicated that the product featured the plate form with 20 and 30g of NaOH addition. Furthermore it was found that the particle size of the product decreased with the addition of NaOH.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.351-355
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• 2001

This research was carried out to find out the possibility of using Faraday's law in analyzing the electrocoagulation system. Bench-scale reactor equipped with aluminum electrode plates was operated using synthetic wastewater which received sodium chloride for conductivity adjustment. Phosphate was added to the wastewater to induce the precipitation with Al. The amount of aluminum dissolved from the electrodes could be predicted by Faraday's law with a difference less than 5%. This difference was greater at a higher electric current, probably due to the increased solution temperature. However, effect of pH on the dissolution of the aluminum was negligible. The result of this study suggested that the operating condition of electrocoagulation system could be developed using the Faraday's law when the pollutant concentration is given.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.477-483
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• 2007

A coagulation process for RO (reverse osmosis) membrane pretreatment system was an effective technology to remove colloidal and particulate matters. However, coagulant residuals from the pretreatment process may negatively affect RO membrane performance. The bench-scale coagulant exposure study was performed to investigate the effect of their residual on adsorbed mass which related to the membrane performance. Coagulant addition in this study ranged from 0 to 5mg/L ferric chloride, alum, and 2mg/L cationic polymer(poly-di-methyldiallyl ammonium chloride) as coagulant aids. This results showed that adsorbed mass is not significantly increased during short-time period, however, accumulated mass of coagulants on the membrane surface is significantly increased during long-time experimental period. The effect of pH on coagulants adsorption characteristics was significantly differed due to the electrostatic repulsive interactions between soluble coagulants and membrane surface charge. This data suggest that the RO membrane performance of drinking water treatment plant could be decreased by adsorption of residual coagulants when applied for the coagulant pretreatment process.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.2
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• pp.295-302
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• 2012

The coagulation of combined sewer overflows ($CSO_{s}$) was investigated by jar-testing with several commercial coagulants. $CSO_{s}$ sample showed different characteristics of coagulation from secondary wastewater with three common coagulants, aluminum sulfate, ferric chloride and polyaluminum chloride (PACl). Jar-tests showed that relatively wide range of optimal SS and T-P removal yielded with alum and ferric chloride compared with cationic polymers, though efficient SS and T-P removal can be achieved with all three coagulants. The decrease of pH was caused by the increase in dosage of aluminum sulfate, ferric chloride and PACl as coagulants. The pH was changed from 7.0 to 4.7 with the dosages of ferric chloride 25 mL/L. Aluminum sulfate revealed pH of 5.0 and PACl was highest pH of 5.4 after dosing of coagulants. The optimal pH to treat $CSO_{s}$ with aluminum sulfate were 6-6.5; with PACl 6-7, and with ferric chloride higher than 7.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.1
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• pp.15-24
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• 2010

Coagulation can be used for pretreatment of NF membrane filtration. Foulants such as organic matter and particulate can be removed effectively with the process while high flux recovery is maintained. Recently various types of polyaluminium coagulants including polyaluminium chloride(PAC) are commercially available for water treatment. This study examines effects of polymeric Al and hydrolysis products of PAC on nanofiltration membrane performance. Dominant hydrolysis products were polymeric Al, $Al(OH)_3$, and ${Al(OH)_4}^{-1}$ at acidic, neutral, and alkaline pH conditions, respectively. Under acidic pH condition, flux decline was increased with increasing PAC concentrations, possibly due to polymeric Al adsorption on membrane pore and/or surfaces. For neutral and alkaline pH conditions, little flux decline was observed with increasing PAC concentrations except the highest ${Al(OH)_4}^{-1}$ concentration, with which rapid flux decline was shown. Removal of ionic matters was also varied with pH conditions in this study. Especially, conductivity removal was substantially low and $Ca^{2+}$ concentration in the permeate was quite high at neutral pH condition.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.05a
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• pp.243-246
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• 2006

수산양식장에서 양식 후 버려지는 패각을 이용하여 인의 제거실험을 하였다. 연속식 실험에서 재순환 하지 않은 경우와 비교할 때 300% 재순환에서는 제거율이 45%정도 증가하였다. 황산알루미늄을 주입한 후 인의 제거율을 비교했을 때 인 제거율이 93%로써 약 70%가 증가하였다. 이에 재순환율의 증가와 응집제의 주입으로 인의 제거율이 크게 향상됨을 알 수 있었다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2004.11a
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• pp.67-70
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• 2004

역세척 후 응집제를 여과사에 주입한 수 여과를 실시한 결과 초기에 높게 나타났던 탁도의 거의 제거되는 것을 알 수 있었으며 pH의 변화에 따른 초기의 탁도 변화는 pH5와 pH7에서 보다 낮은 탁도의 수질을 얻을 수 있었다. pH5부근에서 알루미늄의 존재형태가 $Al(OH)^{2+},\;Al(OH)_2^+$로 많이 존재하며, pH7에서는 $Al(OH)_3$으로 존재하여 모래 표현의 (-) 전하를 감소시킬 수 있는 결과로 판단되었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.26-36
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• 2007

The thermal response characteristics of nozzle liner for a solid rocket motor applying highly aluminized PCP or HTPB propellant with slotted tube grain have been investigated. The SEM photographs of aluminum oxide particles taken from nozzle liner show that the PCP propellant with the finer and less contents of oxidizer can offer greater possibility for increasing aluminum agglomeration than the HTPB propellant. The PCP propellant shows locally greater mechanical erosion at 4 circumferential areas of the nozzle entrance in line with grain slot due to the impingement of large particles, but the HTPB propellant shows greater thermochemical ablation at the nozzle blast tube, the throat insert and the exit cone because of relatively much more mole fraction of $H_2O\;and\;CO_2$ in combustion gases.