Study On Red Tide Organisms Mitigation With Clay Modified By New Types Of Surfactant

In the dissertation, four kinds of surfactants — dialkyl-polyoxyethenyl quaternary ammonium compound (DPQAC), trialkyl-polyoxyethenyl quaternary ammonium compound (TPQAC), C8 Alkyl glucoside quaternary ammonium compound (C8AGQAC), C12 Alkyl glucoside quaternary ammonium compound (C12AGQAC) as the reagents for clay-modification were investigated in the following four fields: (1) the sorption behavior of four kinds of surfactants on clays and the relevant influencing factors; (2) the removal efficiency and influence mechanism of organo-clays against red tide organisms; (3) the kinetics of organo-clays removal red tide organisms; (4) the toxicity of surfactants and the influence of organo-clays on mariculture animals. The four kinds of new type surfactants were first used into red tide management, and the above study was on the basis of the study of our laboratory, the study results could provide valuable evidence for the further study of organo-clays and their application in the management of red tide.Ⅰ. The sorption behavior of four kinds of surfactants — DPQAC, TPQAC, C8AGQAC and C12AGQAC on clays and the relevant influencing factors were investigated, an emphasis was made on their saturate sorption amount. 1. DPQAC and TPQAC could be adsorbed on kaolin and bentonite very quickly, and they could reach equilibration in 2 minutes, the isotherms of their sorption can be described very well by the double-surface Langmuir isotherm. In distilled water the saturate sorption amount of TPQAC on kaolin was about 78 mg/g, but on bentonite was about 224mg/g; the saturate sorption amount of DPQAC on kaolin was about 17 mg/g, but on bentonite was about64mg/g. When in seawater the saturate sorption amount of TPQAC was higher, it was about 260mg/g on kaolin and 1060mg/g on bentonite. So the increase of ion strength can result in the increase of sorption amount.2. The sorption of C8AGQAC and C12AGQAC could reach equilibration in 2 minutes, the isotherms of their sorption can be described very well by the single surface Langmuir isotherm. In distilled water the saturate sorption amount of C12AGQAC on kaolin was about 14.8 mg/g, but on bentonite was about 32.8mg/g; the saturate sorption amount of C8AGQACon kaolin was about 9.9 mg/g, but on bentonite was about 14.8mg/g. When in seawater the saturate sorption amount was higher.3. Diagnostic adsorption apex of clays modified by quaternary ammonium compound could be found in 2925-2928cm"1 and 2854cm"1 by analysis of FT-IR, they were caused by C-H stretching bands of alkyl ammonium cations. And the diagnostic adsorption apex of 1465-1468 cm"1 in the IR spectrum was caused by C-H bending vibration of (CH3)4N+. Therefore the reaction of cation exchange in bentonite modification really took place.II. The influence of DPQAC, TPQAC, C8AGQAC and C12AGQAC on the growth of algae in low concentration and the eradicative effect in high concentration were studied first, and then the removal efficiency of red tide organisms by organo-clays was also investigated.1. The eradicative efficiency of TPQAC Gemini surfactant on red tide organisms was better than DPQAC, it could seriously affect the growth of algae at lmg/L concentration in 3 days and perish algae at 2mg/L concentration in short time period. The algae removal ability of clays modified by two kinds of Gemini surfactants was very good, the removal efficiency could reach 90% at the concentration of 20-30mg/L, while which of rude clays was only about 10-20%, so the modification consumedly improved the efficiency of clays and reduced their concentration, which solved the leavings question of large clay insufflation.2. Two kinds of Alkyl glucoside quaternary ammonium compounds —C8AGQAC and C12AGQAC could seriously affect their growth at l-1.5mg/L concentration in 3 days and eradicate red tide organisms at 1.5-2.5mg/L concentration in 24 hours. Clays modified hy CXAGQAC. anH C12AGQAC had very good ability of flocculating algae, they could form big floccule with algal cells, which was propitious to removing algae. Moreover, the algae removal efficiency of clays modified by Alkyl glucoside quaternary ammonium compound could reach 90% at the concentration of 50mg/L, while which of rude clays was only about 20% at the same concentration, so which also improved the efficiency of clays and reduced their concentration.III. The kinetics of red tide organism coagulation with clays modified by four kinds of surfactants were studied, the effects of different kinds and concentrations of clays, the second component added in clays and the pH of media were examined.1. Two methods of kinetics experiment — methods of spectrophotometer and fluorometry were compared. When using the method of spectrophotometer, the sedimentation kinetics of red tide organism coagulation with clays was well fit for the secondary reaction; but when using the method of fluorometry, it was fit for the hyperbola model much better. Moreover, the experimental results also proved that using fluorometry could avoid the great change of permeance efficiency caused by clays' sedimentation when using spectrophotometer, which availably avoided the influence of clay sedimentation and reflected the essential of algal sedimentation and coagulation well and truly.2. The sedimentation rate of Scrippsiella trochoidea coagulated with clays modified by C12AGQAC was the fastest among four kinds of organo-clays. different kinds and concentrations of clays, the second component added in clays and the pH of media all could influence the sedimentation rate, among which adding the second component in clays was the most efficient method to improve the algal removal efficiency.IV. The toxicity of four kinds of surfactants and the influence of clays modified by them on mariculture animals were examined and the eco-effects of organo-clayswere discussed. In the experiment Penaeus japonicus and Neomysis awatschensis were used as the representative mariculture.1. Firstly the toxicity of DPQAC was examined, its LC50 to the larvae of Penaeus japonicus was 61.9mg/L while to Neomysis awatschensis was 31.8mg/L, so the latter was more sensitive than the former. Meanwhile the results proved that the toxicity of this new type of surfactant was 50 times lower than the conventional ones, clays modified by which did not evidently influence the mariculture when it was used in removing red tide organisms.2. The LC50 of TPQAC to Neomysis awatschensis was 16.7mg/L, and which of C12AGQAC was 17.5mg/L, so their toxicity were all higher than DPQAC, but were still 30 times lower than the conventional ones, clays modified by all of these two types of surfactants did not evidently influence the mariculture when they were used in removing red tide organisms.