Study On Adsorption Mechanism Of Removing Phosphorus By Constructed Wetland Substrate Anthracite

The adsorption characteristics of removing phosphorus in solution byconstructed wetland substrate anthracite was studied through isotherms adsorptionexperiment. The effect of solution concentration, particle size of substrate and pHare investigated. Through adsorption kinetics experiment, the adsorption kineticscharacteristics of anthracite was investigated. We analyzed the effect of temperature,particle size and concentration to the kinetics process of phosphorus adsorption bysubstrate. Adsorption capacity was further investigated. Finally we explored themechanism of phosphorus adsorption by anthracite through the average adsorptionenergy, low temperature nitrogen adsorption, XRD and FTIR etc.Isothermal adsorption experiments showed that Langmuir equation andFreundlich equation can be well described the phosphorus adsorption isothermcharacteristics by anthracite. Langmuir equation can better describe the phosphorusadsorption isotherm characteristics than Freundlich equation. The theoreticaladsorption phosphorus capacity by anthracite is555.56mg/kg.Adsorption factors experiments showed that the best solid liquid ratio ofphosphorus adsorption was2g/50mL.Anthracite adsorption capacity of phosphorus insolution decreased with particle size reducing. Reducing the particle size damagedinternal pore structure of anthracite. Negative effect was produced to improve theadsorption ability. Acidic and alkaline conditions were not conducive to phosphorusabsorption by anthracite. when pH is about7,the phosphorus removal efficiency canreach90%.The adsorption kinetics experiments showed that quasi-second-order equationcan describe the phosphorus removal process by anthracite. The correlationcoefficient is greater than0.96. Elovich and a kinetic equations are not well describedthe phosphorus adsorption kinetics process.Adsorption thermodynamics study showed that the system was△G0>0,△H0<0during the adsorption process of phosphorus by anthracite. It indicates that theadsorption of phosphorus by anthracite is not a spontaneous and exothermic process. The mechanism of phosphorus adsorption was further explored through thecharacterization and structure of anthracite. The results showed that adsorption ofphosphorus by anthracite is mainly physical adsorption and small amounts ofchemical adsorption. Its composition is relatively simple and functional groups is notvery rich. It exists Si-O and CO32-vibration. Anthracite contains microporous,mesoporous and macroporous and mainly is mesoporous. Its specific surface area,pore volume and average pore diameter were0.1677m2/g,0.000769cm3/g,17.89089nm.