Study On The Preparation Of Biomass Sludge Composite Activated Carbon And Its Adsorption Of Sulfomethyl Phenolic Resin Wastewater

Sewage sludge can be used as a potential precursor for the production of adsorbent materials due to its carbon properties.This work studied a new adsorbent that was prepared from sewage sludge by pyrolysis with ZnCl2(as the chemical activation agent),adding biomass materials to improve the carbon content of raw material.This paper discussed the effects of factors by single factor and response surface methodology,and optimized the preparation conditions of sludge biomass composite activated carbon(SBAC):Walnut shell with 20%(wt/wt),activation temperature of 500 ℃,activation time 60 min,activation agent concentration of 2.5 mol· L-1,impregnation ratio of 1:2.5,obtained the SBAC with an iodine index of 574.11 mg · g-1 and a yield of 43.93%.The physical and chemical properties of SBAC were characterized by proximate and ultimate analyses,porous structure analysis,infrared spectrum analysis,determination of bHpzc isoelectric point,Boehm titration and scanning electron microscopy(SEM + EDS)analysis.The speciation analysis of heavy metals showed that pyrolysis largely affected the Cu and Ni in raw materials,and the environment migration and biological utilization was decreased in SBAC,while the environmental risk levels of Cu and Ni were reduced.However,the environmental risk level of Zn was increased in SBAC.Leaching experiment indicated that the Cu,Cr,Cd,Ni leaching concentrations in SBCA were decreased,while the Zn leaching concentration was increased,comparing with sewage sludge.Conclusively,the total content of five kinds of heavy metal were lower than threshold values in standards of pollutants for agricultural sludge in China.The SBAC was used to adsorb SMP in wastewater.The optimal adsorption conditions were acquired by the single factor experiment:the pH of solution was 2.4,the dosage of SBAC was 5 g · L-1,and adsorption time was 50 h to achieve the adsorption equilibrium.The adsorption kinetics data followed a pseudo-second-order kinetic model,and the particle diffusion model showed that suggests that intra-particle and film diffusion were occurring simultaneously in the adsorption process.The result of adsorption isotherms suggests the adsorption behaviors could be described by the Langmuir isotherm model,with a monomolecular layer saturated adsorption capacity of 42.97 mg · g-1.According to the thermodynamic parameters,the adsorption activation energy of 23.95 kJ · mol-1 and the adsorption enthalpy ΔH0 of 7.132-14.41 kJ · mol-1 indicated that the adsorption process was endothermic physical,and the positive adsorption entropy ΔS0 showed that the degrees of freedom was increased in system,the negative Gibbs free energy ΔG0 and positive AH0 indicated that the adsorption was spontaneous and endothermic in nature.Considering its potential low cost of sludge activated carbon,SBAC showed the outstanding adsorption ability for SMP with a highest adsorption capacity of 39.4 mg · g-1,regeneration experiments showed that the regeneration efficiency of SBAC could reached 80.7%,and secondary regeneration efficiency was also higher than 70%.It completely could be satisfied the requirements of practical application.It could be used as a potential low cost adsorbent to treatment drilling wastewater.