| As "green and high quality development" is getting more and more attention,the efficient and high value utilization of resources and environmentally friendly construction of materials have become the focus of both academic and industrial circles.Inorganic pigments are widely used in paints,coatings,printing and dyeing,plastics,etc.Because of their excellent light,heat and weather resistance and more uniform color distribution,they have become indispensable materials in people’s daily life and industrial production.However,most inorganic pigments(such as cadmium red and cadmium yellow)contain toxic heavy metals,which will cause serious environmental pollution and health hazards during production and use,and have been gradually banned in recent years,so it is urgent to develop low-cost,high-efficiency and safe inorganic pigments.Iron-based inorganic pigments are favored because of their rich color range,low cost and non-toxicity,but the production process of traditional iron-based pigments requires the use of concentrated acid and serious environmental pollution.In view of this,this thesis proposes a research idea of in situ mineralization of natural nano-clay induced Fe(Ⅲ)for the preparation of Fe-based hybrid pigments.Using natural clay mineral fiber sepiolite(SEP)as a stable carrier and the only precipitant,one-step hydrot hermal reaction was used to prepare Fe-yellow and Fe-red hybrid pigments with excellent performance,bright color and high stability,respectively,and the structure and properties of the pigments were systematically investigated.The main research contents and results are as follows:(1)The brightly colored and structurally stable iron yellow hybrid pigments were formed by in situ inducing the conversion of Fe(Ⅲ)to hydroxy iron oxide on the surface of natural clay mineral fiber SEP as a carrier and green precipitant.The results show that the negatively charged SEP can adsorb part of Fe(Ⅲ)in solution by electrostatic and ion exchange,and the weakly alkaline SEP can induce the in situ conversion of Fe(Ⅲ)ions to hydroxyiron oxide on its surface under hydrothermal action and anchor stably on the surface of SEP fibers to obtain SEP/α-FeOOH hybrid pigments with one-dimensional fibrous morphology(named as SIY).The colorimetric method of CIE1976L*a*b* version was used to test the color properties of the pigment,and the color parameters of SIY were L*=69.82,a*=14.19,b*=39.54,which were better than those of commercially available iron yellow under high temperature environment.The variation range of Δb* values is within 1.5,0,3.59 and1.5,respectively.Since SIY contains clay,it exhibits better suspension and dispersion than commercially available iron yellow in the dispersion medium.After silane modification,the modified SIY exhibited hydrophobicity and self-cleaning properties(contact angle ≥ 140°).(2)Red iron-based hybrid pigments(SIR)with excellent color properties and stability were prepared by a one-step hydrothermal reaction using nano-clay mineral fiber SEP as a carrier and mineralizer and iron-and aluminum-rich solutions as a source of metal ions.During the hydrothermal reaction,the ions in the solution were converted into Fe/Al oxides,and the color property values of the obtained hybrid pigment SIR were L*=50.66,a*=27.84,and b*=23.34.Through a comparative study with commercial iron red(IY),it was found that SIR has excellent high temperature resistance and no color fading occurred under high temperature environment.At the same time,SIR exhibited excellent light and acid and alkali resistance,with Δa*change values lower than 2.06 and 1.74 after irradiation and chemical treatment,respectively,showing better weathering resistance and chemical stability than commercially available iron yellow pigments.SIR has good dispersion and suspension stability in media,with a liquid height percentage of no less than 98% at settling time.SIR,after silane modification,exhibits hydrophobic properties,with self-cleaning ability and super hydrophobic properties(contact angle ≥ 140°). |
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