铁改性氧化石墨烯壳聚糖对重金属的去除效果

Heavy metals removal by iron modified graphene oxide chitosan

为揭示改性方式对复合材料去除重金属离子的影响,利用浸渍蒸发法和共沉淀法制备铁改性氧化石墨烯壳聚糖复合微球,分别命名为Fe-GOCS和Fe@GOCS。通过批实验,对比分析其在不同水环境(pH=3、7和11)下对As(Ⅴ)、Cu(Ⅱ)、Pb(Ⅱ)和Cd(Ⅱ)的去除效果,并结合FTIR、XRD、SEM和BET表征技术揭示去除机理。结果表明,随pH增加,Fe-GOCS和Fe@GOCS对As(Ⅴ)的去除率(r_(e))呈不同的变化趋势,前者先增加后降低,pH=7时最高r_(e)为56.74%,而后者则逐渐降低,pH=3时r_(e)最大,为87.99%。表征结果证实2种材料对As(Ⅴ)的去除均与Fe—O键有关,去除效果存在差异的主要原因与其不同的载铁形态有关(前者为α-Fe_(2)O_(3),后者为α-FeO(OH))。随pH增加,2种材料对Cu(Ⅱ)和Pb(Ⅱ)的r_(e)均逐渐增大,但去除效果在中性条件下最好,分别为49.45%和23.52%(Fe-GOCS),68.38%和50.85%(Fe@GOCS),但稍差于GOCS;对Cd(Ⅱ)的r_(e)也逐渐增大,但Fe-GOCS的最大r_(e)低于Fe@GOCS,分别为78.30%和99.16%。Cu(Ⅱ)和Pb(Ⅱ)的去除一方面与其离子水解作用有关,另一方面主要通过形成Fe—O—Cu和Fe—O—Pb配合物去除。而Cd(Ⅱ)的去除主要与水解作用有关。循环吸附5次后,Fe@GOCS对As(Ⅴ)的r_(e)仍在80%以上,而Fe-GOCS的再生能力较差。整体上,Fe@GOCS对重金属的去除效果略优于Fe-GOCS,而Fe-GOCS适用的pH范围相对较广。

To reveal the influence of modification methods on heavy metal ions removal by composites,Femodified graphene oxide chitosan composite microspheres were prepared by immersion evaporation and coprecipitation,which were named Fe-GOCS and Fe@GOCS,respectively.Batch experiments were conducted to investigate the removal effects of As(Ⅴ), Cu(Ⅱ), Pb(Ⅱ) and Cd(Ⅱ) in different water environments(pH=3,7 and 11),and the removal mechanism was revealed by FTIR,XRD,SEM and BET characterization techniques.Results showed that:with the increase of pH value,the removal efficiency(r_(e))of As(Ⅴ)by Fe-GOCS and Fe@GOCS showed different trends.The former increased first and then decreased,and the r_(e) reached the maximum value of 56.74%at pH=7,while the latter gradually decreased,and the r_(e) reached the maximum value of 87.99%at pH=3.The characterization results showed that As(Ⅴ)removal by the two materials was related to the Fe-O bond,and the main reason for the difference in the removal effect was related to the different morphology of the iron carrier(α-Fe_(2)O_(3) in the former andα-FeO(OH)in the latter).With the increase of pH,the r_(e) of Cu(Ⅱ)and Pb(Ⅱ)increased gradually,but the removal effect was the best under neutral conditions,which was 49.45%and 23.52%(Fe-GOCS),68.38%and 50.85%(Fe@GOCS),respectively,while they were slightly worse than those of GOCS.The r_(e) of Cd(Ⅱ)also increased gradually,but the maximum r_(e) of Fe-GOCS was lower than Fe@GOCS,which was 78.30%and 99.16%,respectively.The removal of Cu(Ⅱ)and Pb(Ⅱ)was related to ionic hydrolysis on the one hand and mainly through the formation of Fe-O-Cu and Fe-O-Pb complex on the other hand.The removal of Cd(Ⅱ)was mainly related to hydrolysis.After five cycles of adsorption,the r_(e) of As(Ⅴ)by Fe@GOCS was still above 80%,but the regeneration ability of Fe-GOCS was poor.On the whole,the removal effect of Fe@GOCS was slightly better than that of Fe-GOCS,and Fe-GOCS was suitable for a relatively wide pH range.