造纸污泥生物炭对四环素的吸附特性及机理

Adsorption characteristics and mechanism of tetracycline by biochars derived from paper industry sludge

以造纸污泥为原料,在限氧条件下,通过控制热解温度(300,500和700℃),制备生物炭(SBC300、SBC500和SBC700),比较了3种生物炭的基本理化性质;以四环素(TC)为目标污染物,研究了造纸污泥生物炭(SBC)对TC的吸附特性及机理.结果表明,SBC对TC的吸附以化学吸附为主,吸附平衡时,SBC300对TC的去除率最低,为38.8%,SBC700的去除率最高,为54.1%;同时Langmuir模型能更好地描述此吸附过程,且最大吸附量依次为SBC700(63.8mg/g)>SBC500(50.6mg/g)>SBC300(40.0mg/g).热力学分析表明,SBC对TC的吸附为自发且吸热的过程.pH值影响TC的存在形态及SBC的表面带电情况,对吸附过程有较大影响.通过吸附等温线分解法定量描述了表面吸附作用及分配作用的贡献率,结合FTIR分析,表明SBC对TC的吸附可能是分配作用、静电作用、氢键作用、π-πEDA作用及离子交换作用等共同作用的结果.

In this study,the absorption effect of sludge biochar(SBC)prepared with paper industry sludge was investigated by adjusting pyrolysis temperatures(300℃,500℃and 700℃)under oxygen restriction.The physical and chemical properties of three types of biochar(SBC300,SBC500,and SBC700)were compared,along with their characteristics and mechanism of adsorbing TC.The results showed that the adsorption of TC by SBC was dominated by chemical adsorption.At adsorption equilibrium,the removal rate of TC by SBC300 was the least at 38.8%,and the removal rate by SBC700 was the highest at 54.1%.Meanwhile,the Langmuir model better described the adsorption process and the maximum adsorption amount was SBC700(63.8 mg/g)>SBC500(50.6 mg/g)>SBC300(40.0 mg/g),respectively.Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic.And the adsorption process would be greatly affected by p H value as it could influence the existing form of TC and the surface chargeability of SBC.The isotherm decomposition method was used to quantify the contribution of surface adsorption and partition.Combined with FTIR analysis,it indicated that the adsorption process of TC with SBC was the joint effects of partition,electrostatic attraction,hydrogen bonding,π-πEDA and ion exchange.