Abstract:

Sewage sludge and fly ash were used as raw materials and zinc chloride solution with mass fraction of 30% was used as activator to prepare sludge biochar calcined at different temperatures,the sludge biochar was used to treat phosphorus containing wastewater.The effect of sludge biochar on phosphorus removal was investigated through single factor static adsorp-tion experiment and its adsorption mechanism was explored.The results showed that the sludge biochar prepared at 300 ℃ had better phosphorus removal effect.The characterization analysis of raw materials and sludge biochar by scanning electron microscopy（SEM）,specific surface analyzer and fourier infrared spectroscopy（FT-IR） showed that the morphology and surface groups of sludge biochar were significantly changed after calcination,there were many microvoids on the surface of the sample after calcination,and the specific surface area increased to 5.51 m²/g;under the condition of initial mass concent-ration of phosphorus 50 mg/L and the amount of adsorbent 16 g/L,the adsorption reached equilibrium in 90 minutes,and the removal rate of phosphorus was 93.73%;the adsorption process conformed to the quasi second order kinetic equation and the freundlich isotherm adsorption model,and the maximum saturated adsorption capacity was 9.615 mg/g;the whole adsorption process Δ G ⁰<0 and ΔH⁰<0,which was a spontaneous exothermic process.In addition to physical adsorption,the adsorption process also involves electron pair coordination between phosphate and—OH or C—O covalent bond of adsorbent,which was a physical-chemical composite adsorption; the fifth adsorption capacity of the adsorbent was 85.74% of the first adsorption capacity,showing good regeneration performance.

Key words: sludge biochar, phosphorus removal rate, adsorption mechanism, dynamics, thermodynamics