Research On Geochemistry And Application Of Pelagic Clay From Chinese Investigation Area Of East Pacific Ocean

The sea clay has been paid attention by people since in 1930s, for the firsttime, foreign scholars discovered that the clay minerals, such as illite,montmorillonite and kaolinite, in the sediments from the Pacific are endowedwith crystal character. From then on, the research atmosphere on the sea claysediments has been activated, and while in 1960s, correlative works on thetype, distribution, cause of formation, and etc of the sea clay minerals.appeared one after the other. Nevertheless, our country began to study on it inlater period of 1970s, and in the middle stage of 1980s, investigations on theocean clay minerals, most of which is from the Pacific, started as well. The seaclay was mainly used for reflecting the change of the geologic environments,such as ancient geography, ancient climate, and ancient environment, due to itpossessing minute grain, out-of-order structure and variable composition. sothe research passion has been gone down to now.Investigation of the clay from the east Pacific, which was made to reflectthe change of the geologic environments, has already been exceedingly mature,especially the research on geochemistry characteristics of the REEs insediments and its indication meaning for the clay minerals. However, study onthe application of the ocean clay has not been reported yet. The resourcepotentiality of the clay and ooze in the world ocean is so tremendous, theamount of which is 2.1×10⁷km³ and 3.1×10⁷km³ respectively according to thereported data, that the application and development of these resources willhave significant meanings, in particular as the reserve resources. But first ofall, the geochemistry of pelagic clay should been researched and thenaccording the character to design the application research. Research on nanomaterial is the most important thing in the material preparation. It isrecognized that nano material is the most prospective material for 21 th century.Nesoporous material is a freshly inorganic non-metallic material. Since itsparticular structure and property it will have extensive application. So toprepare the nano/mesoporous material with pelagic clay is very important notonly in the application of sea clay but also in the material preparation. The paper contains five sections. They are geochemistry character ofpelagic clay sediments, purification and white increasing of pelagic clay.organic activation of pelagic clay, nano amorpher silica preparation withpelagic clay, crystal and mesoporous alumina reclaim from the deposed liquid.By test and analysis of the clay sediments, including mineral composition,chemical component, crystal structure, physical-chemistry properties, and etc,it demonstrates that the pelagic clay is provided with the characteristics ofminute granule, out-of-order structure, abundant organic substances and REEs.Bleaching test on the pelagic clay was carried out by adopting the chemicalreduction method and surface modification of the clay was conducted too.According the grain constitutes and the clay mineral's structure we preparedthe nano/mesoporous silica and alumina and optimized the technics parameters.The conclusions are as follow:1. The geochemical character of clay sedimentsThere are seven kind of mineral compositions in the area of China investigation. Themain constituent is clay mineral whose content is much more (>70%). exceptthat several samples are carbonate sediments. Their main mineral constituent isirregular I/S mixed layer, with a small quantity of kaolinite and chlorite.Feldspars and quartz were also detected. The quantity of organic substances.most of which is more than 1%, with the minority reached 10%. is greaterwhile comparing with the homogeneous clay in earths surface. Chemicalcomposition of the representative clay sediments shows that the ocean clay isabundant in REEs, and iron, manganese oxides content is larger which resultsin the low whiteness of the samples. As a result of the physical-chemistryproperties test of the ocean clay, the granule is fine, the crystallization is bad,and its microcosmical conformation is mainly of floccule and sandwich.2. Purification and white increasing of pelagic clayTo purify the pelagic clay with the method of suspend pervasion, theresult is that by drying the clay sediments and remake the slurry is better thanthe method of make the slurry directly, and the purity pelagic clay isincompact grain.In order to increase the whiteness of pelagic clay we performed it by using acid dissolving hydrogen reduction method just after a great number ofexperiment methods were tried. The specific surface area of pelagic clay isincreased, and the dispersing ability in organic solvent becomes better whileincreasing its whiteness. The optimized conditions are vitriol 25%, reducer2.0g/L, solid to liquid 4:1, reacting time 4h. The whiteness will increasedabout 49% at best, and 98.5% iron can be removed. To calcine the pelagic clayat 800℃can increase the clay whiteness too.3. Organic activation of pelagic clayThe purified sample was modified by mechanical chemistry surfacemodification method. After a series of modification conditions, modifiers, andetc were sieved, we draw a conclusion that the silane and alminate are the bestmodifiers. The water-absorbing ratio of the modified sample decreasesobviously, and its dispersing ability in organic medium improves evidently.X-ray diffraction analysis indicates that the out-of-order degree of the claymineral increases after modification, and the space between layers increase too.which demonstrates that organic modifier takes up partly interspaces betweenthe layers of the clay, improving the water absorbing ability between the layers.thus, in favour of the sample dispersing in organic medium easier. In the sameway, that the ratio surface area of the modified sample decreases is the resultof the modifier molecules entering the structure of the clay, and stuffing uppartial pores while grinding.Wet modification was the process of organic activation, during which thewashed, filtrated cake of the acid treated sample was made into slurryimmediately, and modified by adding into modifiers in the course of stirring. Itreveals that the modified result is the best when the slurry thickness was 30%,reaction time was 40 minutes, and the added silane quantity was 3.0%.4. Nano amorpher silica preparation with pelagic clayWe investigate the leaching ratio of aluminum by acid soakage and alkalimelting. The result of acid soakage shows that the leaching ratio of aluminumhas not passed 50%, subordinate to the intending result. The result of alkalimelting shows that the leaching ratio of aluminum has achieved 100%, thebest synthesis condition is: More effective alkali to destroy the crystal structure of abyssal clay is NaOH, the dosage is 2.5272 g (the dosage ofabyssal clay is 1.0000 g); smelting temperature is 650℃; the time of smeltingis 30 min. silicon component exist in form of solvable liquor.Base on the specific surface area testing, there many factors influence itsspecific surface area as the dosage of dispersant, age time, and sinteringtemperature. The best synthesis conditions to acquire largest specific surfacearea are as below: gelatin liquor s volume is 40 mL(0.01 g/mL), the dosage ofhydrochloric acid is 6 mL, and the adding speed of acid is 3 mL/min; the agetime is 12 h; washing the filter residue to get pH=5-6, the sinteringtemperature is 700℃, then the product get max specific surface area, the datais 1056 m²Â·g^-1. compare with the flocculent and flake pattern of abyssal, theporous silica is branch-like or mesh-like pattern. So the porous silica haspotential to be modified.The transformation of abyssal to porous silica is detected by IR analysiswhen use alkali melting it. The acid adding system influence the structure ofsamples, the experiment approve that, at the low speed of acid adding, theproducts hold large specific surface area. Compare with many dispersant,samples hold most priority properties while use gelatin as dispersant.5. Nano and mesoporous alumina reclaim from the deposed liquidAdd NH₃.H₂O to the liquid after amorpher silica preparation, andgain the sediments. Use NaOH solution to redissolve the sediments, and let theA1³⁺ separated from other ions. Add CO₂ gas to the solution and let NaAlO₂hydrolyae to form Al(OH)₃. To calcine the Al(OH)₃ we can gain theα-Al₂O₃.The optimized technic conditions are taking polyethylene glycol 6000 as thedispersant agent, stirring it for 0.5h, adding CO₂ let PH=6.0, stirring 2h,plating it for 24h, to calcine it at 1200℃for ln, we can get theα-Al₂O₃.SEM testing indicates that the grains of Al₂O₃ are smaller than 100nm.The optimized preparation conditions of mesoporours Al₂O₃ areneutralizing the Al(OH)₃ to A1(NO₃)₃, adding the mobile agent 1.5g and100ml0.5mol/L NH₃·H₂O to 18 mlAl(NO₃)₃ solution, stirring and heating it to75℃, using 1mol/L HNO₃ and 1mol/L NH₃·H₂O to accommodate the PH ofsolution, stirring it at 75℃for 140min, and the gelatine was obtained. Plating the gelatine at the room temperature for 48h, drying it at 80℃, to calcine it at250℃and holding the temperature for 1.5h, to rise the temperature to 500℃,holding the temperature for 4h, we can gain the mesoporous Al₂O₃. N₂absorption testing states that the porous of alumina are equality and theaperture is about 2.6 nm.By recycling the alumina the solution changed from acidity to neutralitywhich prevents the environmental pollution.