Effect of Hydrogen Peroxide on the Treatment of High Boron Concentration Wastewater by Chemical Precipitation Method
| Autor: | Wei-ShengLan, 藍韋盛 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 Boron is one of trace nutrient the human beings demand. However, high concentrated boron in the environment is harmful for the organism. In biological field, high concentration of boron causes poor growth of plant. Therefore, both World Health Organization (WHO) and European Union (EU) have set up a standard of 0.3 mg-B/L in drinking water. In Taiwan, EPA legislated for limiting the industry effluent lower than 1 mg-B/L. Electrocoagulation method (EC) is newly in disposal of the high concentrated boron wastewater. In contrast, although the chemical precipitation has lower efficiency on boron removal than EC, the cost effect and energy consumption have it still popular in real water management. In preliminary test, perborate which is the oxidation state of boron compounds can be reduced by chemical precipitation directly using Ca coagulant. Thus, this work aimed at exploring a novel chemical precipitation preconditioning with an oxidation process for managing the target boron compounds, including boric acid, metaorate, borax and perborate, in a concentration of 1000 mg-B/L. In oxidation stage, the hydrogen peroxide was an effective oxidant for pretreating the boron compounds. The efficiency of hydrogen peroxide could lead to around 80 % boron removal, which was independent of solution pH. In chemical precipitation stage, the effects of II A group cations, including Mg, Ca, Sr, and Ba, and solution pH were assessed to achieve high boron removal. The experimental results suggested that the efficiency for coagulating the oxidized boron compounds were 98 %, 87 %, 86%, and 42 % using Ba, Ca, Sr, and Mg coagulants, respectively. Meanwhile, the precipitation tended to highest level of 98% boron removal under the optimal chemical dosages, adopting the molar ratio of H2O2 to boron around 1.5 and Ba to boron around 0.75, and pH higher than 9 as well. Afterward, the precipitation of oxidized boron compounds by barium has proven to produce the crystallized power of BaB2O4(OH)4 phase, which can be seen as a recoverable resource. This work has demonstrated a potential oxidation-chemical precipitation process for resolving the defects of traditional chemical precipitation on boron removal (〈 15 %). By pretreating with a suitable oxidant, then precipitation using effective cations, the relatively higher boron removal (98 %) than the new electrocoagulation method (80 %) has been attained. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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