二硫代羧基改性小麦秸秆及其制备产生的废滤液对水中Cu(Ⅱ)的去除性能与机理

The removal performance and mechanism of dithiocarboxyl wheat straw and the waste filtrate generated during its preparation process for Cu(Ⅱ) in water

为了提升小麦秸秆对废水中Cu(Ⅱ)的吸附性能和实现废滤液的综合利用,采用二硫代羧基改性小麦秸秆(DTWS)作为吸附剂和DTWS制备过程中产生的废滤液(DTWSF)作为絮凝剂,探究它们对水样中Cu(Ⅱ)的去除效果.通过吸附实验和絮凝实验分别确定DTWS和DTWSF对Cu(Ⅱ)的去除性能.利用各种表征方法探究DTWS和DTWSF对Cu(Ⅱ)的去除机理.结果表明,当振荡速率为200 r·min^(-1)、吸附温度为50℃、吸附时间为120 min时,DTWS对Cu(Ⅱ)初始浓度为50 mg·L^(-1)、pH值为6.0水样中Cu(Ⅱ)的吸附性能最优,Cu(Ⅱ)的去除率为98.20%,而DTWSF对该含Cu(Ⅱ)水样中Cu(Ⅱ)的最高去除率可达99.02%.扫描电镜结果显示吸附Cu(Ⅱ)后的DTWS表面出现突起的颗粒状,能谱图中吸附后的DTWS-Cu与絮凝后的DTWSF-Cu新增Cu含量分别为3.65%、27.17%,红外谱图中羟基(-OH)、二硫代羧基(-C(=S)-SH)等相关特征峰的强度及位置均发生变化.DTWS对Cu(Ⅱ)的吸附机理主要包括配位作用、静电吸附作用和物理吸附作用,DTWSF对Cu(Ⅱ)的絮凝机理主要为配位作用、吸附架桥作用和网捕卷扫作用.

In order to enhance the adsorption performance of wheat straw for Cu(Ⅱ) in wastewater and achieve the comprehensive utilization of waste filtrate,wheat straw modified with dithiocarboxylate groups was employed as the adsorbent(DTWS),and the waste filtrate generated during the preparation process was utilized as the flocculant(DTWSF).The removal performance of Cu(Ⅱ) by DTWS and DTWSF in water samples were investigated through adsorption and flocculation experiments.Various characterization methods were utilized to investigate the removal mechanisms of Cu(Ⅱ) by DTWS and DTWSF.The results showed that under optimal conditions including an initial Cu(Ⅱ) concentration of 50 mg·L^(-1),pH value at 6.0,shaking rate at 200 r·min^(-1),adsorption temperature at 50 ° C,and an adsorption time of 120 min,DTWS exhibited excellent adsorption performance with a remarkable removal rate of 98.20% for Cu(II) in water sample.Additionally,DTWSF achieved a maximum removal rate of 99.02%for Cu(Ⅱ) in water sample.Scanning electron microscopy(SEM) analysis revealed that granular structures on the surface of DTWS after absorbing Cu(II),while energy-dispersive spectroscopy(EDS) analysis indicated that copper contents in DTWS-Cu and DTWSF-Cu after adsorption and flocculation as 3.65% and 27.17%,respectively.Infrared spectroscopy(IR) analysis showed changes in intensities and positions related to hydroxyl groups(-OH) and dithiocarboxylate groups(-C(=S)-SH),suggesting modifications on the surface of DTWS occurred upon interaction with Cu(II).The main adsorption mechanism involved coordination,electrostatic adsorption,and physical adsorption for Cu(II)-DTWS interactions;whereas coordination,adsorption bridging action along with net sweep action played significant roles during Cu(II)-DTWSF interactions.