| Coal is not only natural adsorbent but also good materials to prepare adsorbent owing to various oxygen-containing groups and pore structure. The specific surface area and pore volume increase with the size of coal particles decreasing during superfine pulverization. New pores will be formed and the adsorption capacities will be enhanced when coal particles accumulated together compactly. It is valuable to prepare coal based superfine composite adsorbent both in probing new ways of coal utilization and in preparing coal based adsorbents with high capacity. In this paper, based on the studies of mechanism and relationships of coal powders, especially superfine coal powders with adsorption capacity. Two methods both mechanochemistry and liquid phase chemical oxidization were used to prepare coal based superfine composite adsorbents. Adsorption capacity and mechanism of phenol, aniline, nitrobenzene and nickel ion (Ni2+) onto coal based superfine composite adsorbents were studied respectively compared with commercial coal based activated carbon.The kinetic studies showed that phenol adsorption onto various size coal powders accords with the second order model, the processes were controlled both by film and pore diffusion. The effective diffusion coefficient and rate constant of intraparticle transport were calculated. The relationship between diameter of coal powders and phenoladsorption capacity conforms to equation: q = 28.1378 exp+ 24.1453.The adsorption equilibrium of phenol onto various size coal powders can be described in terms of the Freundlich or Langmuir isotherm. Phenol adsorption capacity onto superfine coal powders decrease with increasing temperature. The adsorption parameters of thermodynamics H is -11.18kJ-mol-1. S is-23.39J mol-1-K-1,G are negative.Phenol adsorption capacity increases when coal powder was milled together with KMnO4. Infrared spectra (FTIR) showed that mechanochemistry reaction occurred and the resultants mainly were humic acid salt during milling. When the mass ratio of KMnO4 to coal was 10:100, after 6h milled coal powder was washed with alkali solution, acid solution and distilled water, then treated with microwave radiation for 15 minutes under 540W after dried. Coal based superfine composite adsorbent was obtained standing for MMCA. Scanning electron microscope (SEM) analysis of section showed that MMCA was made up of a lot of small particles conglutination with each other, diameter of the smaller particles are 200nm,the bigger particles are 500nm.There are abundant pores in MMCA.The phenol adsorption capacity increased when superfine coal powder was oxidized by H2O2 rnoderately. Coal powder was rinsed with alkali solution, acid solution and distilled water respectively after oxidized by H2O2 under conditions that mass ratio of H2O2 to coal was 0.23, concentration 2M and temperature 20 C.The mixture was filtrated and the residue was dried (sample standing for HCA). Coal based superfine composite adsorbent standing for AHCA obtained after impregnated in acetone and dried. SEM analysis of sections showed that AHCA is made up of a lot of small particles conglutination with each other, diameter of the smaller particles are 200nm,the bigger particles are about 500nm.There are abundant pores in AHCA.The kinetics of phenol, aniline, nitrobenzene and Ni2+ adsorbed respectively onto coal based superfine composite adsorbents fit the second order kinetic model. The adsorption processes were controlled by both film and pore diffusion except nitrobenzene adsorption onto MMCA which was controlled by pore diffusion. The effective diffusion coefficient and rate constant of intraparticle transport were calculated. The order of adsorption capacities of phenol, aniline, nitrobenzene onto four kinds of adsorbents in turns was CAC>AHCA>HCA>MMCA, however Ni2+ was MMCA> AHCA>CAC>HCA. The adsorption equilibrium of phenol, aniline, nitrobenzene and Ni2+ onto four kinds of coal based adsorbents can be described in terms of the Langmuir or Freundlich isotherm.Phenol adsorption c...
|
PDF Full Text Request