Lead adsorption properties of a sludge adsorbent prepared from sludge and coal

A sludge adsorbent was prepared by pyrolysis from wastewater treatment plant sludge and coal.The adsorbent was used to adsorb Pb2+ from simulated wastewater.The influences of pyrolysis temperature,mass ratio of coal with sludge,pyrolysis time and diameter of particles on iodine adsorption value and yield were studied,as well as adsorption time,temperature,pH values and the adsorbent amount on adsorption effect.The optimum conditions for the preparation of sludge adsorbent were a pyrolysis temperature of 900℃,mass ratio of coal of 20%,pyrolysis time of 60 min,and diameter of particles 10~20 mesh.The iodine absorption value of sludge adsorbent is 321.62 mg · g-1,the yield is 44.85%,and the specific surface area is 189.23 m2 · g-1.The adsorption of Pb2+ increases with the adsorption time,temperature,pH value and adsorbent amount,until equilibrium is reached.The adsorption kinetics of Pb2+ in the sludge adsorbent accords with the pseudo-second-order kinetics equation and the two-step adsorption kinetics rate equation.The adsorption rate is not only controlled by intra-particle diffusion but also by extra-particle diffusion.Compared with the Freundlich isotherm equation,the Langmuir isotherm equation is more appropriate to describe the adsorption behavior.