• Clean Technology
• /
• v.18 no.4
• /
• pp.404-409
• /
• 2012

In this study, the effects of mixing intensity and coagulant dosages on the characteristics of floc growth for phosphorus removal were investigated. The experiments were conducted under Al/P molar ratio of 1.0, 1.5 and 2.0; rapid mixing intensity with G value of 100, 300, and 500 $s^{-1}$. The characteristics of floc growth were measured by flocculation index (FSI) and the removal efficiencies of phosphorus by using different size filters. The removal efficiencies of soluble phosphorus increased as Al/P molar ratio and rapid mixing intensity increased. However, the highest removal efficiencies of T-P were observed at G value of 300 $s^{-1}$. When Al/P molar ratio was lower than 1.0, the value of FSI at G value of 500 $s^{-1}$ was the largest. However, when Al/P ratio was larger than 1.0, the value of FSI at G value 300 $s^{-1}$ was the largest. Effects of mixing intensity and Al/P molar ratio on coagulation for phosphorus removal of synthetic and real wastewater effluent were observed to be similar.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.8
• /
• pp.549-556
• /
• 2012

T-P removal efficiency was analyzed according to the metal to initial T-P ratio (mole basis) with respect to the samples from different WWTPs having various initial T-P and SS conditions. Also, operating costs were calculated based on the injected coagulant amount and the amount of sludge production. Most experiments were conducted by the standard jar-test protocol. Molar ratio of coagulant dose was varied considerably according to the initial SS concentration range in secondary clarifier effluent samples which had above 0.5 mg/L of initial T-P. Based on 90% T-P removal efficiency, results were: At the initial SS range of below 10 mg/L, Alum (8%) = 11 mol Al/mol P needed and PAC (17%) = 9.6 mol Al/mol P needed; At the initial SS range of above 10 mg/L, Alum (8%) = 3.9 mol Al/mol P needed and PAC (17%) = 3.2 mol Al/mol P needed.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.8
• /
• pp.428-434
• /
• 2016

This study evaluated the efficacy of Ti-based coagulants on phosphorus (P) removal from municipal wastewater and compared them with Al-based coagulants. Jar test experiments were performed at various chemical doses and OH/Ti molar ratio (B value). The higher the intial phosphate ($PO_4-P$) concentration, the lower the [Ti]/[P] to reach a residual concentration below 0.2 mg P/L. Removal efficiencies of total phosphorus increased with an increased coagulant dose but decreased after the efficiencies reached their maximum value regardless of coagulant or B value. On the other hand, $PO_4-P$ removal showed an increasing trend with an increased coagulant dose, reaching the plateau value under large coagulant dose conditions for both Ti- and Al-based coagulants regardless of B value. The chemical dose of Ti-based coagulants was approximately twice higher than that of Al-based coagulants with the same P-removal efficiency. The coagulation efficiency was influenced by different B values.

• The Korean Journal of Ecology
• /
• v.28 no.6
• /
• pp.389-393
• /
• 2005

This study was carried out to investigate the effects of soil acidification on the growth of 3-year-old Pinus densiflora seedlings grown for 21 weeks in brown forest soils acidified with $H_2SO_4$ solution. The concentrations of Al in the acidified soils were increased with increasing amount of $H^+$ added to the soil. The total dry weight of the seedlings was reduced by the addition of the $H_2SO_4$ solution. In addition, there was a strong positive correlation (r=0.97, p<0.01) between the dry weight of the seedlings and the molar (Ca+Mg+K)/Al ratio of the soil. The seedlings with the molar (Ca+Mg+K)/Al ratio of 1.0 resulted from approximately 50% growth reduction compared with the control value. The results suggest that the molar (Ca+Mg+K)/Al ratio of the soil may be a useful indicator for assessing the critical load of acid deposition.

• Applied Chemistry for Engineering
• /
• v.28 no.5
• /
• pp.521-528
• /
• 2017

To find a recycling method for waste liquid crystal display (LCD) panel glasses, we investigated the synthesis process of zeolite with an ion exchange ability by hydrothermal reaction using waste LCD panel glass as a raw material. It was shown that the waste LCD panel glass can be used as a raw material for the production of zeolites having the ion exchange ability. Following conditions for the synthesis of the zeolite with an ion exchange ability were required : the molar ratio of Si to Al components of the waste LCD glass needs to be 2.0 to 2.8, and the temperature of $100^{\circ}C$ and reaction time of 12 hours are needed for the hydrothermal reaction. Based on the required conditions previously mentioned, the A type zeolite was synthesized when the molar ratio of the Si to Al component was 2.0, and the P type zeolite was produced when the molar ratio was 2.8. The type A zeolite synthesized by using the waste LCD panel glass showed a good ion exchange ability and heavy metal adsorption ability. Also, an excellent ion exchange capacity was observed as the crystal phase grows stably in a cubic phase.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.4
• /
• pp.231-236
• /
• 2011

The effects of magnesium and calcium ions on phosphorus removal by aluminium coagulation were investigated with various jar tests using settled raw sewage. Maximum TP (total phosphate) removal occurred at pH around 5~6 with aluminium coagulation, and it decreased above pH 6. TP and $H_nPO_4^{n-3}$ removal efficiencies, however, were kept above 95% at pH above 6 by adding the divalent metallic ions like magnesium or calcium ions on aluminium coagulation process. At molar ratio of Al/P ($Al^{3+}/H_nPO_4^{n-3}$) above 3, TP removal efficiency was as high as 80%, and residual TP less than 0.2 mg/L occurred at Al/P ratio above 6. TP removal efficiency was improved by adding magnesium or calcium ions and the optimum $Al^{3+}/Mg^{2+}$ and $Al^{3+}/Ca^{2+}$ ratios were about 2. The required dose of aluminium coagulant was reduced for equivalent amount of TP removal by adding magnesium or calcium ions, as a result sludge generation was also reduced.

• Journal of Korean Society of Forest Science
• /
• v.97 no.3
• /
• pp.266-273
• /
• 2008

The effects of soil acidification on the seedling growth and nutrition of Pinus densiflora and Quercus acutissima were investigated. The relationship between the seedling growth and molar (Ca+Mg+K)/Al ratio of in soil solution was examined. The results suggested that growth inhibition of seedling Pinus densiflora and Quercus acutissima was due to the low pH of soil solution, which was followed by leach of Al into soil solution, and decrease of essential elements, such as Ca in aerial pant of the seeding caused by the increase of Al concentration in subterranean pant of the seedlings. The level of growth inhibition was determined not only by Al concentration, but also by the balance of inorganic elements, Al, Ca, Mg and K. The growths of two species in total dry weight were clearly inhibited when molar (Ca+Mg+K)/Al ratio of the soil was lower than 6.0. The growth in dry weight, in the condition of the molar ratio was 0.8, was decreased 60% or 50% for the seedling of Pinus densiflora or Quercus acutissima respectively. It was concluded that the molar (Ca+Mg+K)/ Al ratio could be an important index for evaluation of the effects of soil acidification, due to acid deposition such as acid rain, on growth of trees and nutrition. And it might be a more useful indicator for evaluation of critical load of acid deposition on forest ecosystems.

• Journal of Korean Society of Forest Science
• /
• v.87 no.4
• /
• pp.611-619
• /
• 1998

This study was carried out to examine the effects of soil acidification on growth and nutrient status of 2 - year - old Pious densiflora Sieb. et Zucc. seedlings grown for 120 days in brown forest soils acidified with $H_2SO_4$ solution with or without leaching rations from the soil. The concentrations of A1 in the acidified soils increased with increasing amount of $H^+$ added to the soil. The total dry weight of the seedlings was decreased by the addition of the $H_2SO_4$ solution. The increase of Al concentration in the belowground part resulted from the decreased concentration of essential mineral elements such as Ca and Mg in the aboveground part. In addition, a strong positive correlation(r=0.96, p<0.001) was observed between the dry weight of the seedlings and the molar (Ca+Mg+K)/A1 ratio of the soil solution. When the molar (Ca+Mg+K)/Al ratio was approximately 7.0, the dry weight of the seedlings began to decrease compared with that of the seedlings in the control treatment. The seedlings with the molar (Ca+Mg+K)/Al ratio of 1.0 resulted from approximately 40% growth reduction compared with the control value. The results suggest that the molar (Ca+Mg+K)/Al ratio of the soil solution may be a useful indicator for assessing the critical load of acid deposition.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.3
• /
• pp.66-74
• /
• 1999

InAlGaAs/InGaAs HBTs with the various emitter junction gradings(xf=0.0-1.0) and the modified collector structures (collector- I;n-p-n, collector-II;i-p-n) are simulated and analyzed by HMC (Hybrid Monte Carlo) method in order to find an optimum structure for the shortest transit time. A minimum base transit time($ au$b) of 0.21ps was obtainsed for HBT with the grading layer, which is parabolically graded from $x_f$=1.0 and xf=0.5 at the emitter-base interface. The minimum collector transit time($\tau$c) of 0.31ps was found when the collector was modified by inserting p-p-n layers, because p layer makes it possible to relax the electric field in the i-type collector layer, confining the electrons in the $\Gamma$-valley during transporting across the collector. Thus InAlGaAs/InGaAs HBT in combination with the emitter grading($x_f$=0.5) and the modified collector-III showed the transit times of 0.87 psec and the cut-off frequency (f$\tau$) of 183 GHz.

• Journal of the Korean Ceramic Society
• /
• v.28 no.5
• /
• pp.373-382
• /
• 1991

The effect of Ca/P mole ratio (Ca/P=1.60, 1.67, 1.75) in the initial solution on the mechanical properties of alumina added hydroxyapatite was investigated. Hydroxyapatite was synthesized by precipitation method using Ca(NO3)2$.$4H2O and (NH4)2HPO4 as starting materials and 5 wt% of ${\alpha}$-Al2O3 was added to precipitation solution. The powder was calcined at 800$^{\circ}C$ and sintered at 1,150∼1,400$^{\circ}C$ under water vapor atmosphere. With the increasing of Ca/P mole ration in the initial solution, the amount of tricalcium phosphate formed from the decomposition of hydroxyapatite reduced and the sinterability and mechanical properties were increased. The bending strength and Vickers hardness of the specimen sintered at 1,300$^{\circ}C$ with the Ca/P mole ratio of 1.75 in the initial solution were 230 MPa and 650 kg/$\textrm{mm}^2$, respectively. The improvement of mechanical properties was attributed to not only the effect of Ca/P mole ratio but also the strengthening of sintered body by Al substitution for P ions.