A Preliminary Study On The Formation Mechanism Of Halloysite From Weathering

As one of the most commonly seen clay minerals,Kaolin group minerals are widely used in industrial applications.Halloysite,has a great industrial value for its special hollow tubular structure as well as its high biocompatibility.However,this value has been greatly impaired by the challenges in purification and separation of this often low nature reserved Halloysite from associated mineral impurities like kaolinite,quartz,feldspar,mica,iron oxide,etc.In this paper,X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were used to compare the mineral composition and formation of Suzhou and Maanshan hydrothermal kaolin hydrothermal kaolin,Jingdezhen Kaolin derived from weathering,and Mangnong sedimentary kaolin in Inner Mongolia,as well as their transformation process from original rock minerals to kaolin group minerals.Result:Large amount of halloysite was observed in hydrothermal and leaching forming kaolin and exists several possible reaction sequences:Albite?Halloysite.K-feldspar?Kaolinite,and Muscovite?Halloysite;but none halloysite was observed in sedimentary kaolin.Extra attention was paid to the Halloysite from the weathering of Muscovite on Jingdezhen weathered granite.Through detailed observation on weathered muscovite,it is found that the Halloysite weathered from muscovite can be divided into two categories based on their formation and spatial distribution:Most of the halloysite is present as long filaments with a uniform occurrence and is found on both the exposed(001)surfaces and edges of muscovite.In contrast,a small amount of the halloysite-like mineral occurs as stumpy,sheet stacking,which has an irregular appearance and occurs mainly at the margins of the muscovite plates.It is proposed that the halloysite was derived from the surface leaching of muscovite by two possible mechanisms:dissolution-precipitation or local dissolution-rearrangement of residue structure.Based on the observation of geological,This study was designed and carried out the simulating muscovite weathering experiment of Halloysite formation,dissolved muscovite was observed and part of the plates curled like tiles,or more like filaments,this indicate the formation of halloysite by mode of local dissolution-rearrangement of residue structure.