Fe、Mn、Cu及其复合负载γ-Al2O3纳米颗粒的制备、表征和催化降解PVA性能

Preparation,characterization and catalytic performance of Fe,Mn,Cu and complex metallic oxides supported on γ-Al_2O_3

采用浸渍-煅烧法制备了Fe、Mn、Cu及其复合负载的γ-Al_2O_3纳米颗粒,采用了SEM-EDS、BET以及XRD等方法对制备得到的Mn_xO_y/γ-Al_2O_3、Cu_xO_y/γ-Al_2O_3、FexOy/γ-Al_2O_3以及FexCuyMnzOw/γ-Al_2O_3纳米颗粒进行了表征.结果表明,通过浸渍-煅烧法得到的四种纳米颗粒催化剂均可以和双氧水形成非均相类Fenton反应体系,产生大量羟基自由基,从而有效降解PVA大分子,降低废水中的PVA浓度.另外还通过BoxBehnken Design响应面分析法分别确定了Mn_xO_y/γ-Al_2O_3、Cu_xO_y/γ-Al_2O_3、FexOy/γ-Al_2O_3以及FexCuyMnzOw/γ-Al_2O_3纳米颗粒催化双氧水降解处理PVA的最佳工艺参数.利用GPC和GC-MS分析进一步表征PVA在不同催化剂条件下得到的降解产物后,分析结果表明:Fe、Mn、Cu复合负载的FexCuyMnzOw/γ-Al_2O_3纳米颗粒催化双氧水降解PVA的催化效果相对较好.当PVA初始反应浓度为1%,反应温度为60℃,催化剂投加量为0.5 g·L^(-1),双氧水投加量为60 mL·L^(-1)时,PVA的浓度下降率可以达到95%以上,降解产物粘均分子量达到1395,分子量下降率达到99%,降解小分子产物主要包括丁酮、苯甲醛、己醛以及乙酸等不饱和小分子.

MnxOy/γ-Al2O3,CuxOy/γ-Al2O3,FexOy/γ-Al2O3 and FexCuyMnzOw/γ-Al2O3 nano particles were prepared by a wet impregnation-calcination method and characterized by SEM-EDS,BET and XRD.Results revealed that the prepared MnxOy/γ-Al2O3,CuxOy/γ-Al2O3,FexOy/γ-Al2O3 and FexCuyMnzOw/γ-Al2O3 nano particles rapidly reacted with H2 O2 and produced large quantity of hydroxyl radicals.With the oxidation by hydroxyl radicals in heterogeneous Fenton-like process,PVA macromolecules in solution was effectively degraded and hence removed in aqueous solution.The Box-Behnken response surface analysis method was employed to investigate theoptimum degradation parameters of PVA using MnxOy/γ-Al2O3,CuxOy/γ-Al2O3,FexOy/γ-Al2O3 and FexCuyMnzOw/γ-Al2O3 particles.Gel permeation chromatography（GPC） and gas chromatography-mass spectrometry（GC-MS） were also used to further identify the products of PVA under different catalyst conditions.It demonstrated that the catalytic performance of FexCuyMnzOw/γ-Al2O3 particles was better than other three catalysts.The PVA removal efficiency was above 95 %while the reaction temperature was 60 ℃,initial concentration of PVA was 1 %,H2O2 dosage was60 min·L^-1 and FexCuyMnzOw/γ-Al2O3 dosage was 0.5 g·L^-1 respectively.Besides,the GPC detection also confirmed that PVA was effectively oxidized with a decreasing rate of about 99 %,for the molecular weight from 100773 to 1395.Based on GC-MS analysis,it turned out that the degradation products of PVA mainly included several unsaturated compounds of lower molecular weight,such as butanone,benzaldehyde,hexanal and acetic acid,etc.