Effect And Mechanism Of Coking Sludge On The Structure And Properties Of Activated Carbon

Coking sludge is an industrial solid waste produced from coking wastewater treatment,and.It has been drawn more and more attention due to it is harmful to environment and difficult to treatment.With the promulgation of the 12 th Five Year Plan for national environmental protection,the traditional disposal methods of sludge,such as landfill,incineration and sea transportation,are not meeting the current environmental protection requirements.Therefore,it is imperative to use coking sludge reasonably and effectively.It is considered as a safe and effective way of utilizing sludge resource disposal for activated carbon?AC?preparation.In this paper,Yangcheng coal?YC?,Xiangyuan coal?XY?,Datong Coal?DT?and Changzhi coking plant sludge were used as raw materials,asphalt and coal tar were used as binder to prepare AC through steam activation.The effects of different coal types and the amount of sludge addition on the AC's structure and performance were investigated.The main research contents and conclusions are as follows:?1?The structure of AC with different coal types was investigated.The pore structure of AC is changed when sludge was added to high-rank coal.When the amount of coking sludge is 20%,the AC specific surface area of XY and YC were 662 m²/g and574 m²/g respectively.The content of basic groups on the AC surface increased by adding the low-rang coal,and it reached 1.58 mmol/g by adding 20% sludge to DT.?2?The effect of sludge's addition as well as AC structure was investigated.AC was prepared by YC and coking sludge.With the amount of sludge increased,the weight loss of carbonization gradually increased,and the weight loss first increased and then almost no change,resulting in the yield gradually decreased.When the amount of sludge's addition from 0 to 10%,the AC specific surface area increased and microporous structure was enhanced.The maximum specific surface area of AC achieved 759m²/g.The AC's diameter of pore becomes larger and the specific surface area decreases with increased addition of sludge.The sludge contains a large amount of alkali metals and alkaline earth metals,which can promote the formation of basic groups on the AC surface during steam activation.With the increase of sludge addition,the content of alkaline functional groupson the surface of AC increased gradually.The basic groups on the surface of AC achieve1.58 mmol/g when the amount of sludge is 100%.?3?The effect of the amount of sludge on the adsorption performance of Pb²⁺ onto AC was investigated.It is found that the addition of sludge can promote the adsorption of Pb²⁺ onto AC.The optimum amount of sludge is 50%,which the adsorption efficiency of Pb²⁺ can reach up to 111 mg/g,and it is 146% higher than that of unmodified AC.The adsorption of Pb²⁺ onto AC follows the pseudo-second-order model,and the adsorption isotherm is efficiently modelled by the Langmuir equation.The mechanism of Pb²⁺ onto AC is the extraction by surface basic groups,cation exchange and precipitation.Therefore,the metal cations and the basic groups of the AC surface increased with the amount of sludge increased,which promoted the adsorption of Pb²⁺.