硝酸改性生物炭对水体中阴阳离子染料吸附特性

Adsorption Characterization of Cationic and Anionic Dye from Aqueous Solution by HNO_3 Modified Biochar

以玉米秸秆为原料,并利用HNO_3改性得到改性生物炭HN4CS和HN8CS。以亚甲基蓝(MB)和活性艳蓝(KNR)分别代表阳离子和阴离子染料,研究了改性生物炭对水体中阴阳离子染料的吸附特征和机制。结果表明,HN4CS含有丰富的含氧官能团,HN8CS表面以醇、酚的-OH为主;改性增加了生物炭的中孔体积,但比表面积、微孔体积和pH减少。改性生物炭对阴阳离子染料的吸附是多种机制共同作用的结果,其中对阳离子染料的吸附速率受液膜扩散和颗粒内扩散共同控制,对阴离子染料的吸附速率主要受颗粒内扩散控制。改性生物炭对阴阳离子染料的吸附机制:分子间氢键、离子交换和静电作用的共同作用是对阳离子染料的吸附机制;π-π色散力作用和静电作用控制了改性生物炭对阴离子染料的吸附机制。

Modified biochars HN4CS and HN8CS was prepared by agricultural residues and modified by HNO3. The adsorption characteristics and mechanisms of anionic and cationic dye in water by modified biochars were researched, the methylene blue(MB) and reactive brilliant blue(KNR) representing cationic dye and anionic dye respectively. The results showed that HN4CS had abundant oxygen-containing functional groups, and there were many phenolic hydroxyls on HN8CS surface. In addition, modification with HNO3 increased the mesopore volumes, but reduced the surface areas, micropore volumes and pH. Cationic and anionic dye adsorption on HNO3-modifid biochars being heterogeneous could be controlled by multiple mechanisms, cationic dye adsorption rate was controlled by liquid membrane diffusion and intraparticle diffusion, anionic dye adsorption rate was mainly controlled by intraparticle diffusion. HNO3-modified biochars had different mechanisms for cationic and anionic dye adsorption: the cation exchange between oxygen-containing function groups and cationic dye(predominating adsorption mechanism), along with intermolecular hydrogen bonding and electrostatic interactions are proposed to be the mechanism of cationic dye adsorption. The π-π interactions between anionic dye and phenolic hydroxyls, along with electrostatic interactions is proposed to be the mechanisms of anionic dye adsorption.