Browsing by Author "Chu, CP"

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Expression dewatering of alum-coagulated clay slurries
(1997-05-01)
Chang, IL
;
Chu, CP
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
Filtration followed by expression characteristics of the alum-coagulated clay slurries are first reported in this paper. A strong correlation between alum chemistry and the dewatering efficiency exists. At pH 3, where the positively charged ions are the dominating species, the alum addition has only a minor improvement on dewatering efficiency. At pH 7 and pH 10, where sweep flocs enmeshment play the major role, dewatering performance improves continuously as alum dose increases. At pH 5.2, where a charge reversal regime exists, the dewatering efficiency exhibits a reversal phenomenon as well. The overall dewaterability follows: pH 5.2 > pH 3 > pH 7 > pH 10. A complete test consists of the filtration and expression stages, which are discussed separately. The filtration stage is discussed based on the average specific resistance and the residual moisture in the filtration cake. The expression stage is discussed based on the combined Terzaghi-Voigt rheological model, from which the fraction contributed by the secondary consolidation (B) and the particle creeping factor (eta) are evaluated. For the dewatering sake, a lower B and a higher eta are desired. Both parameters B and eta increase at elevated alum dose and/or lower pH value, while exhibiting a local minimum in charge reversal regime at pH 5.2. The optimal alum dose considering sludge dewaterability is discussed.
Expression dewatering of alum-coagulated clay slurries
(1997-05-01)
Chang, IL
;
Chu, CP
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
Filtration followed by expression characteristics of the alum-coagulated clay slurries are first reported in this paper. A strong correlation between alum chemistry and the dewatering efficiency exists. At pH 3, where the positively charged ions are the dominating species, the alum addition has only a minor improvement on dewatering efficiency. At pH 7 and pH 10, where sweep flocs enmeshment play the major role, dewatering performance improves continuously as alum dose increases. At pH 5.2, where a charge reversal regime exists, the dewatering efficiency exhibits a reversal phenomenon as well. The overall dewaterability follows: pH 5.2 > pH 3 > pH 7 > pH 10. A complete test consists of the filtration and expression stages, which are discussed separately. The filtration stage is discussed based on the average specific resistance and the residual moisture in the filtration cake. The expression stage is discussed based on the combined Terzaghi-Voigt rheological model, from which the fraction contributed by the secondary consolidation (B) and the particle creeping factor (eta) are evaluated. For the dewatering sake, a lower B and a higher eta are desired. Both parameters B and eta increase at elevated alum dose and/or lower pH value, while exhibiting a local minimum in charge reversal regime at pH 5.2. The optimal alum dose considering sludge dewaterability is discussed.
Polymer dose effects on filtration followed by expression of clay slurries
(1997-01-15)
Chang, IL
;
Chu, CP
;
Lee, DJ
;
Huang, C
;
環境工程研究所
Filtration followed by expression characteristics of cationic polymer conditioned clay slurries are reported for the first time in this work. As the polymer dosage increases, the resistance to filtration greatly decreases until a specific dose has been reached, where the zeta potential is close to zero. And further increase in polymer dose conversely raises the resistance. The expression data are interpreted by the Terzaghi-Voigt combined model, from which the model parameters are evaluated. The polymer conditioning has only a mild effect on the primary consolidation process but has, however, a considerable influence on secondary consolidation characteristics. When zeta potential changes from negative to positive, both the easiness of creeping of constituent particles within the sludge cake and the fraction of moisture removal by the secondary consolidation attain a maximum., The optimal polymer dose criterion considering the filtration and expression stages separately, or in combination, is (sic). (C) 1997 Academic Press
Temperature-dependent photoluminescence of highly strained InGaAsN/GaAs quantum wells (lambda=1.28-1.45 mu m) with GaAsP strain-compensated layers
(2005-08-01)
Lai, FI
;
Kuo, HC
;
Chang, YH
;
Tsai, MY
;
Chu, CP
The effects of nitrogen incorporation into the In(0.4)Ga(0.6)As(1-x)N(x)/GaAs single quantum wells (SQWs), where x = 0.5 and 2%, grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) were investigated using photoluminescence (PL) and high-resolution transmission electron microscopy (HRTEM). The evolution of the excitation-dependent PL and PL-peak position with temperature between 10 and 300 K shows that quantum-dot-like states occurred at that high nitrogen incorporation (x = 2%) and were confirmed by an HRTEM image which showed small dark regions about 2 - 3 nm in size was found in the interface of In(0.4)Ga(0.6)As(0.98)N(0.02) and GaAs. Our investigations indicate that high nitrogen incorporation into the In(0.4)Ga(0.6)As(1-x)N(x)/GaAs system influenced carrier localization and might cause the formation of the dot-like states.
The role of ionic surfactants in compression dewatering of alum sludge
(1998-10-01)
Chu, CP
;
Lee, DJ
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
This work has experimentally investigated the characteristics of filtration followed by consolidation dewatering of an alum sludge, with especial attention to the effects of adding ionic surfactants (SDS or CTAB), The filtration and consolidation stages at a pressure of 3000 psi were discussed separately, The efficiency of filtration is enhanced in the presence of surfactant molecules; however, the cationic surfactant (CTAB) raises the consolidation rate while the anionic surfactant (SDS) retards it, A newly proposed rheological model has been employed for interpreting the consolidation data. CTAB would not alter markedly the moisture distribution in the sludge, but SDS does increase markedly the amount of the tightly bound moisture by diminishing the portion occupied by pore water. The possible role of surfactants in the sludge flocs is considered. Both surfactants can be used as conditioning aids during the filtration stage. However, the applications of SDS to the consolidation stage are not encouraged. (C) 1998 Academic Press.