| Gasification slag（GS）is a large amount of solid waste produced by coal gasification.It has great pollution to the environment,and the output is large and difficult to deal with.The GS is composed of carbon residue and inorganic minerals,which restrict the utilization of gasification slag.The inorganic minerals in the GS mainly include Si,Al,Ca and other elements,among which Si and Al are essential elements for the structure of zeolite.If properly treated,can make the GS“waste into treasure”.In this paper,the gasification slag-based ammonia-nitrogen adsorbent was prepared by hydrothermal synthesis using RCS,an intermediate product which accounted for the largest proportion of the gasification slag after its separation by hydrocyclone.The effects of the addition amount of Na Al O2,Na OH,hydrothermal time and hydrothermal temperature on the adsorption performance of the hydrothermal synthesized adsorbent were investigated by the control variable method.The RCS and adsorbent were characterized by XRD,nitrogen adsorption-desorption,ICP,Fourier transform infrared（FTIR）,and Zeta potential.The influence of carbon residue and inorganic minerals in the RCS on the adsorption performance of ammonia nitrogen（NH4-N）was determined by pickling and low temperature calcination for ash removal of RCS.The single factor method was used to investigate the effects of initial solution p H,initial concentration of NH4-N and adsorbent to solution solid-to-liquid ratio on the removal rate of NH4-N.The adsorption isotherm and adsorption kinetic equation of the experimental data were fitted to determine the adsorption behavior of the adsorbent to NH4-N.The main conclusions are shown below:（1）The optimum conditions for the preparation of the adsorbent were as follows:mass ratio Na OH:RCS:Na Al O2=6:5:1,hydrothermal temperature 100℃,hydrothermal time 12h.The initial concentration of NH4-N is 60 mg/L,the initial p H of the solution is 6.86,the contact time is 1 min,and the solid-liquid ratio is 40 g/L.Under these conditions,the removal rate of ammonia nitrogen can reach 82.31%.（2）The specific surface area of RCS increased from 267 m2/g to 311 m2/g after hydrothermal activation.At the same p H,the electronegativity of the adsorbent is better than that of the RCS.In non-strong acid environment,the negative charge on the surface of the adsorbent is much higher than that of the RCS,which is beneficial to the removal of NH4-N.（3）In this experimental system,the ash in RCS can form zeolite structure which is easy to exchange ionic ammonia after hydrothermal treatment,thus increasing the removal rate of NH4-N as adsorbent.The residual carbon in RCS can promote the activation of ash in the hydrothermal process.The carbon in the adsorbent can make the hydrothermal synthesis of zeolite structure attached to its surface,thus increasing the adsorption performance of the adsorbent to NH4-N.（4）The Freundlich equation has a high fitting degree to the experimental data,indicating that the adsorption of NH4-N by adsorbents is mainly multi-molecule adsorption.The adsorption behavior of the adsorbent on NH4-N was consistent with the quasi-first-order kinetic equation,and the adsorption capacity of lily calculated by the quasi-first-order kinetic equation was close to the experimental data,indicating that the adsorption of NH4-N by the adsorbent was mainly physical adsorption. |
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