銀改質合成之二氧化鈦奈米管對砷之去除

Synthesis of Ag-modified TNT for removal of arsenic

王敏仲(Ming-Chong Wang)

指導教授 ： 劉振宇

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201900562

摘要

本研究利用二氧化鈦奈米管光催化材料搭配吸附法去除水中三價砷以及五價砷，另外，為增加其對三價砷之光催氧化能力，分別以不同重量比例(5%、10%及20%)銀化合物(AgNO3)改質TNT製成Ag(5)−TNT、Ag(10)−TNT及Ag(20)−TNT，並比較改質前後對砷去除的差異影響。結果顯示TNT、Ag(5)−TNT、Ag(10)−TNT及Ag(20)−TNT四種材料(80 mg)對五價砷(10 ppm)去除效果可分別達到79.8%、90.2%、94.1%及86.8%，由許多實驗可看出四種材料中Ag(10)-TNT具有最佳的去除效果。而在不同pH值條件下對五價砷以及三價砷去除效率，隨著水體pH值增加而逐漸降低。競爭吸附實驗方面，使用硫酸鹽及磷酸鹽作為對砷的競爭吸附物種，由於TNT以及Ag(5)−TNT、Ag(10)−TNT及Ag(20)−TNT等材料對砷的鍵結能力大於硫酸鹽，因此硫酸鹽干擾競爭吸附能力相對磷酸鹽較低，添加15 ppm磷酸鹽會造成吸附率降低30%−40%。光催氧化實驗方面，四種材料皆有氧化三價砷的能力，在一小時的紫外光照射催化下40 mg的TNT、Ag(5)−TNT、Ag(10)−TNT及Ag(20)−TNT可使10 ppm的三價砷完全去除，而反應後水中五價砷濃度分別剩餘4.43、3.9、3.3及4.7 ppm。實驗進一步探討添加抗壞血酸、氟離子及第三丁醇，研究氧化效率的變化以及推論TNT對三價砷的氧化機制。連續式吸附實驗使用TNT以及Ag(10)−TNT搭配吸附床對五價砷濃度1 ppm進行8小時的連續吸附，結果顯示最高去除率可達96%以上，實驗也使用地下水進行實際應用，TNT以及Ag(10)−TNT可使1 ppm砷濃度降低至接近砷安全含量標準10 ppb。

關鍵字

砷 ； 奈米鈦管 ； 銀改質 ； 光催化 ； 吸附

並列摘要

In this study, titanium dioxide nanotube (TNT) and Ag-modified TNT that were synthesized by adding different weight of AgNO3 were applied to remove arsenite (As3+) and arsenate (As5+) in solution. The results showed that the removal efficiencies of TNT, Ag(5)-TNT, Ag(10)-TNT and Ag(20)-TNT for As5+ (10 ppm) were 79.8%, 90.2%, 94.1%, and 86.8%, respectively. Ag(10)-TNT possessed the best removal efficiency for As5+ which compared with other samples. Moreover, the removal efficiency decreased with increasing pH value. For competitive adsorption experiments, phosphate had greater influence than sulfate for TNT samples on adsorption of arsenic species. The removal efficiency dropped about 30%−40% when added 15 ppm phosphate in solution. All resultant TNT samples can oxidize As3+ when UV irradiation was applied. The resultant samples (40 mg) can oxidize 10 ppm As3+ completely, and remained 3.3−4.7 ppm of As5+ in solution. In order to investigate the oxidized mechanism of TNT sample for As3+, ascorbic acid, fluoride ion, and third butanol were also added. Furthermore, TNT and Ag(10)-TNT were utilized to remove As5+ (1 ppm) in continuous adsorption experiments and the removal efficiency reached 96%. After TNT and Ag(10)-TNT treatment, the groundwater that contain 1 ppm As5+ can nearly meet the standard of 10 ppb.

並列關鍵字

arsenic ； TiO2 nanotubes ； argentum modification ； photocatalysis ； adsorption

參考文獻

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