| With the rapid progress of industrialization and urbanization in China,the problem of heavy metal pollution in China is becoming more and more prominent.The disordered emission of all kinds of mining waste,electroplating waste water,metallurgy and metal processing wastewater is making the heavy metal pollution emerge in endlessly.The excess sludge as a product of urban sewage treatment has the characteristics of adsorption of heavy metal ions.The excess sludge can not only remove heavy metal ions in water,but also can achieve the effect of waste treatment.It is of great significance and application value to study the adsorption characteristics of heavy metal ions in water by residual sludge.This paper mainly studies the adsorption of heavy metal ions include Cu2+and Pb2+by excess sludge,NaOH modified sludge and H3PO4 modified sludge,discusses the main factors affecting the removal of copper and lead ions by adsorbents and the differences in adsorption capacity of copper ions and lead ions.The adsorption model of copper ion and lead ion by different adsorbents was fitted by the isothermal adsorption model and the kinetic adsorption model.The adsorption properties of the three kinds of adsorbents were characterized by scanning electron microscopy,specific surface area and infrared atlas.The results showed that the maximum adsorption capacity of unmodified sludge to Cu2+and Pb2+were 39.42mg/g and 65.04mg/g,respectively;the maximum adsorption capacity of NaOH modified sludge to Cu2+and Pb2+were 46.86mg/g and 72.54mg/g,increased by 18.87%and 11.53%,respectively;the maximum adsorption capacity of H3PO4 modified sludge to Cu2+and Pb2+were 55.62mg/g and 86.79mg/g,increased by 41.09%and 21.75%,respectively.Through comparison,it is found that the adsorption effect of these three adsorbents on Pb2+is better than that of Cu2+.It is found that the initial solution concentration,adsorbent dosage,pH value,adsorption reaction time and competitive ion have great influence on the adsorption effect.Increasing the temperature will slightly increase the adsorption capacity,but it has little effect.Langmuir isothermal adsorption model can describe the adsorption process of copper ions and lead ions by excess sludge,NaOH modified sludge and H3PO4 modified sludge.In kinetic analysis,the adsorption process of excess sludge,NaOH modified sludge and H3PO4modified sludge is more consistent with the quasi two stage kinetic model,and there is chemical process in adsorption.By means of scanning electron microscopy,the modified residual sludge particles are smaller,the surface is more rough and the surface area is increased. |
