Study On Absorption Of Ionized Nitrogen By Carbonized Wheat Straw

To make wheat straw residue recyclable and to be uses in suit, the wheat strawwas used as the biochar adsorbent by means of physical modification. According tothe static and dynamic adsorption experiments, the present article is aimed at thestudy on the waste water treatment efficiency by using carbonized wheat straw.It is easy to make the water eutrophication by discharge the ammonia nitrogeninto water environment. At present, biological treatment method, chemical processingmethod and physical and chemical treatment method are the fundamental methods fortreating the ammonia nitrogen wastewater. But the adsorption method is an importantmethod for treating the ammonia nitrogen, which had a widely application in theindustry. The absorbent which made by wheat straw is not only an inexpensiveabsorbent but also an ecologically material.The adsorption performance on ionized ammonia of carbonized wheat straw wasinvestigated by testing ammonium ion initial concentration, solution pH value,solid-liquid ratio, oscillation time and temperature. The adsorbed ions ammoniumadsorption balance and thermodynamic and kinetic characteristics were also studied.The dynamic data were discussed with pseudo-first-order equation, pseudo-second-or-der equation and Elovich equation data. Its adsorption mechanism was also analyzedwith the diffusion equation in the granules. The adsorption isotherm was fitted withlinear fit by using Langmuir equation and Freundlich equation. Free energy change（G）, entropy change （S） and enthalpy getting （H） were calculatedsimultaneously.The effect of initial concentration of ammonium ion, velocity, initial pH valueand adding quantity of the absorbent on breakthrough curve was discussed byutilizing kinetic adsorption research on adsorbed ions ammonium as the foundation.With the fixed bed mathematical model and Thomas model, different dosing quantity,different initial concentration and different pH value adsorption were fitted to thedata.From static adsorption test, the carbonization wheat straw surface structure isgood for the adsorption of ammonium ion compared with wheat straw which was notcarbonized, the highest adsorption removal rate for ammonium ion increased from20%to61.41%.The best carbonization temperature of preparing wheat strawadsorbent with direct carbonization method was300℃.The best adsorption quantitcan reach3.179mg·g-1when the carbonization temperature was25℃, pH was9, thesolid-liquid ratio was6g·L^-1, adsorption oscillation time was6hours. The different quality adsorption concentration (ρ=30mg·L^-1,50mg·L^-1,100mg·L^-1) ofcarbonized wheat straw can accords with accurate pseudo-second-order dynamicsmodel, the adsorption constants k2were0.6818,0.7474,1.0250(g·（mg·min）^-1)respectively at300℃; The best temperature for ammonia nitrogen removal adsorptionby directly carbonized wheat straw absorbent was30℃; The adsorption isotherm withdifferent temperature can be fit with Freundlich adsorption isotherm equation; Byusing adsorption thermodynamics equation, the equivalent enthalpy change is positive（H>0）, adsorption freedom change is negative （G <0）, adsorption entropy changeis positive （S>0）, which showed that the carbonization wheat straw for ammoniumions adsorption was a endothermic process and belonged to the physical adsorption.From dynamic test, the locus of breakthrough curve shifted left with the increaseof the initial concentration of ammonium ion, flow velocity, the pH and reducing ofdosing quantity. The carbonization wheat straw for ammonium ions adsorptiondynamics can be well described through the rate constant, correlation coefficient, theequilibrium adsorption and dynamic parameters with fixed bed mathematical model.Thomas simulation model can also describe the dynamic adsorption of carbonizationwheat straw for ammonium ion adsorption.