Preparation Of Ni-P/ACFs Compound And Study On Its Catalytic Performance

In recent years, microwave technology is successfully applied in the environmentalmonitoring and treatments of waste water, waste gas and solid waste, renowned as the “greenchemical reaction technology” and paid much attention by wide scholars. Compared to thetraditional heating technology, microwave heating has advantages: selective heating,rapidness and efficience, the device of minor volume, no production of waste, energyconservation, cleanliness and easy control. Microwave has both thermal effect andnon-thermal effect. Thermal effect results in the high temperature of the medium and thenorganic pollutants are degraded by high temperature oxidation. The non-thermal effect canresult in the fierce oscillation of molecules, the rupture of chemical bond, the alteration ofreaction course, the decrease of reaction activation energy, the acceleration of reaction rate,the enhancement of equilibrium conversion, the reduction of by-product and the change ofstereoselectivity. Thus organic pollutants are degraded.Nickel phosphide in transition-metal phosphide, especially with Ni/P>1attractextensive research interest due to a series of phase (such as Ni₂P, Ni₃P, Ni5P2, Ni8P3andNi₁₂P₅) and broad industrial application especially in catalysis. Nickel with nanoscale is agood magnetic material, which has very strong microwave absorbing property. Due toelectronic flaws of nickel, nickel phosphide has better properties than metal nickel. In recentyears, the photocatalytic property of nickel phosphide is investigated. Activated carbon ascatalyst of microwave induced chemical reaction is widely studied. Activated carbon fiber isa new type of microporous activated carbon containing disordered graphite and a modern andhighly porous carbon material. Compared to the traditional powder or granular form, it hasmany important advantages. Combination between ACF and the catalyst shows bettercatalytic property and regeneration capacity.We selected silkworm cocoon as precursor of activated carbon fiber in this work and silkactivated carbon fiber were prepared by activation with CO₂and KOH. XRD revealed thatCO₂activation retained the turbostratic graphite structure and KOH activation destroyed theturbostratic graphite structure. FT-IR indicated that amounts of oxygen containing functional groups after the activation with CO₂and KOH increased. SEM results showed that CSACFand KSACF were both the structure of porous fiber and EDS analysis showed that CSACFwas more suitable for the preparation of Ni-P/ACF.N2adsorption-desorption isotherm andpore size distribution curve indicated that CSACF was a kind of mesoporous material andKSACF was a kind of microporous material; The specific surface area of CSACF-3andKSACF-3reaches as high as1379.82m²/g and2797.30m²/g, respectively. ACF with highspecific surface area was prepared by KOH activation. Study on the adsorption kinetics andadsorption isotherm showed that compared with other dynamic models, thePseudo-second-order model was the most suitable dynamic model of MB adsorbed ontoCSACF-3and KSACF-3; The equilibrium adsorption capacity of CSACF-3and KSACF-3were515.46mg/g and512.82mg/g, respectively. Langmuir model is the most suitableadsorption isotherm model of two kinds of activated carbon fiber; the maximum monolayeradsorption capacity of CSACF-3and KSACF-3was757.58mg/g and1090.21mg/g,respectively; the adsorption of MB onto ACF is a favorable and physical adsorption. Theincrease of pH can improve the equilibrium adsorption capacity of MB onto ACF.Ni-P/ACF catalyst was prepared by impregnation and calcination method usingCSACF-3as support. XRD analysis showed that only NiO existed in the catalyst at500℃and Ni-P system produced above600℃; the amount of the loading did not affect the phasecomposition of catalyst. SEM showed that Ni-P/ACF retained the fibrous morphology ofCSACF; there was a pore-forming process during the calcination; the amount of the loadingaffected the surface morphology of catalyst. N2adsorption-desorption isotherm indicated theprepared catalyst had abundant micropore and higher SBET;with the increase of loading, thespecific surface area of Ni-P/ACF decreased, the SBETof Ni-P/ACF catalyst with the loadingof40%was still up to450m²/g. Study on catalytic kinetics indicted that photocatalytic andmicrowave induced catalytic process conformed to the first-order reaction kinetics.A series offactors affecting the photocatalytic performance and microwave-induced catalytic propertywere investigated in this work. Photocatalytic tests showed that the prepared Ni-P/ACFscatalyst had good photocatalytic property, the degradation rate of Acid fuchsin under visiblelight and UV-light during360min was82.6%and100%, respectively; the degradation rateand reaction rate increased with the loading; compared to NiO, Ni-P system had better photocatalytic property; the concentration of solution was an important factor affecting thereaction rate, reaction rate linearly decreased with the concentration which is no more than20mg/L; the degradation rate and reaction rate increased with the dosage of Ni-P/ACF catalystand the more suitable dosage was30mg; the catalyst can be repeatedly used and thedegradation rate of Acid fuchsin by catalyst under UV-light was still up to91.7%after thefifth times. Microwave induced catalytic tests indicated that the degradation rate of Acidfuchsin by Ni-P/ACFs catalyst prepared at600℃was above95%;when the loading wassmaller，the adsorption property of ACF was the control step; when the loading was bigger,the catalytic property of catalyst played a leading role; Compared to NiO, Ni had strongermicrowave absorbing property; the degradation rate increased with the power of microwaveand the dosage of catalyst and reaction rate linearly increased with the power of microwaveand the dosage of catalyst; the degradation rate and reaction rate decreased with theconcentration of the solution; when the catalyst was repeatedly used, the pretreatment by MWbefore using was in favor of the regeneration of the catalytic property of the catalyst, but thedegradation rate and reaction rate decreased with the using times in a long run; thephotocatalytic process did not affect the morphology and phase of the catalyst, however，NiOgenerated and the grain size of Ni became larger. Finally, the catalytic mechanism waspreliminarily discussed by the change of pH and conductivity in the solution and FTIR ofAcid fushcin.