丙烯酸钠-玉米芯接枝共聚物的制备及其对Ni2+的吸附机制

为探索利用农业废弃物玉米芯制备高效吸附材料去除水溶液中重金属离子的可行性。利用原子转移自由基聚合(ATRP)技术将大量对重金属离子具有较强亲和能力的羧基嫁接到玉米芯表面，制备出丙烯酸钠-玉米芯接枝共聚物(MC-g-PGMA-g-PAA-Na)，同时采用热重、FTIR、SEM、EDS和XPS对吸附Ni2+前后的吸附材料进行表征，研究其吸附机制。结果表明MC-g-PGMA-g-PAA-Na可以有效地去除水溶液中的Ni2+，其羧基含量达到6.02 mmol·g?1，是改性前的35.4倍。MC-g-PGMA-g-PAA-Na与含有Ni2+溶液接触后，主要是其含有的羧基吸附了溶液中Ni2+，并形成了羧酸镍，吸附前后Ni2+的价态没有发生变化，羧基与Ni2+的配位方式主要是双齿桥式。同时MC-g-PGMA-g-PAA-Na含有的Na+全部释放到溶液中，说明该吸附过程伴有Na+与Ni2+的阳离子交换。 

Preparation of sodium acrylate-corncobs graft copolymers and its adsorption mechanism for Ni2+

In order to explore the feasibility of preparing high-efficiency adsorption material with agricultural waste corncobs as raw material to remove heavy metal ions from aqueous solution, a large number of carboxyl groups with strong affinity for heavy metal ions were grafted onto the surface of corncobs using atom transfer radical polymerization (ATRP) technology to obtain the sodium acrylate-corncobs graft copolymers (MC-g-PGMA-g-PAA-Na). Thermogravimetry, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray energy spectrum (EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize MC-g-PGMA-g-PAA-Na before and after adsorption of Ni2+ for studying its adsorption mechanism. The results show that MC-g-PGMA-g-PAA-Na can effectively remove Ni2+ in aqueous solution. The carboxyl content in MC-g-PGMA-g-PAA-Na reaches 6.02 mmol·g?1 and is 35.4 times that before modification. It is proved that when MC-g-PGMA-g-PAA-Na is contacted with a solution containing Ni2+, the carboxyl groups contained in MC-g-PGMA-g-PAA-Na act on Ni2+ to adsorb Ni2+ in the solution and form carboxylic acid nickel. The valence of Ni2+ do not change before and after adsorption. The coordination mode of carboxyl and Ni2+ is mainly a bidentate bridge. At the same time, all Na+ contained in MC-g-PGMA-g-PAA-Na are released into the solution, indicating that the process of adsorption of Ni2+ in the solution is accompanied by cation exchange between Na+ and Ni2+.