Studies On Mechanism And Methodology Of Organo-clay In Removing Red Tide Organisms

Harmful algal blooms (HABs), so called "red tides", now occur annually in manycoastal waters and cause grievous environmental problems even poison human. Manyworld organizations and state governments have focus their attentions on studyingbloom dynamics and finding out the promising and effective management methods.Scattering clay is thought as one of the most promising methods though the algalremoval by natural clays is not efficient enough. In this dissertation we importedhexadecyltrimethylammonium (HDTMA) into clays when we prepared organo-clays toovercome clay shortcomings of low removal efficiencies and deficient flocculation.Firstly, characteristics and influencing factors of HDTMA adsorption in kaolinite andmontmorillonite were studied. Results indicated that HDTMA adsorption bymontmorillonite was not identical to that by kaolinite. According to the optimizedmethod different organo-clays were prepared. Secondly, algal removal efficiencies bythe different organo-clays were examined. Results suggested that the algal removalefficiency by clay was considerably improved by HDTMA modification. The mainfactors influencing the efficiencies of the organo-clays were clay types, adsorption ofHDTMA, incubation time, ion strength and reaction temperature. Thirdly, the influencesof HDTMA on the algal physiological functions were measured and themicro-structures of algae stressed by HDTMA and flocculated with organo-clayparticles were observed separately through transmission electron microscope (TEM)and scanning electron microscope (SEM). Results indicated that HDTMA in metastablestate in organo-clays might be one of the key factors which determined algal removalefficiency. Our results also showed that HDTMA could improve clay flocculation withred tide algae. Lastly, the influence of organo-clay on mariculture animals wasexamined and the eco-effects of organo-clay were discussed. The best way of thecomplexes application was studied and the corresponding mesocosm tests (CEPEX) inEast China Sea were conducted in April and May in 2003. The results revealed that theorgano-clays could effectively remove red tide organisms without evident harm tomariculture animals.