不同表面處理生物炭對磷酸鹽吸附行為之影響

台灣坡地農業普遍，山坡地超限利用常使水庫優養化，水質劣化。為解決優養化帶來的水質污染，本研究嘗試模擬應用表面處理之生物炭於坡地土壤中，先行吸附固定非點源污染物，如磷酸鹽。本研究將未處理生物炭 (CK)以0.1 M之鹽酸進行酸洗1小時，得酸洗生物炭 (Acid-treated Biochar; ATB)，且利用金屬氧化物對磷酸鹽專一性吸附之特性，將鐵共沉澱於酸洗生物炭表面上形成鐵複合生物炭 (Fe-treated biochar; FeTB)，探討不同表面處理之生物炭對磷酸鹽在pH=7的環境下之吸附效能，最後應用Langmuir等溫吸附模型得出最大吸附量。試驗結果指出，不同表面處理生物炭之吸附量隨著初始濃度增加而提高，當P濃度為500 mg/L時，未處理之生物炭 (CK)最大吸附量為55.5 mg/g、酸洗生物炭(ATB) 為56.8 mg/g，而鐵複合生物炭 (FeTB)在相同條件下之吸附量為 327.8 mg/g。Langmuir等溫吸附模型中，不同表面處理生物炭之吸附模式皆符合此等溫吸附式，其相關係數R值皆大於0.96，且Langmuir 等溫吸附模型推估ATB和FeTB之最大吸附量為104.9 mg/g及325.8 mg/g，前者與實際實驗結果差將近50 mg/g，而後者與實際結果相近。由電子微探儀之元素分布圖可發現，FeTB於吸附後，鐵與磷酸鹽之點位重疊率高，而ATB上磷的吸附位置，主要在生物炭表面之金屬物 (鎂、鉀)上。由此可知FeTB能有效保留金屬氧化物本身對磷酸鹽之特性，並增加生物炭對磷的吸附效果。

關鍵字

優養化；非點源汙染；生物炭；磷酸鹽；吸附

並列摘要

Agriculture on slopes is common in Taiwan, and the overuse of hillsides often leads to optimal maintenance of reservoirs and deterioration of water quality. In order to solve the water pollution caused by optimization, this thesis tried to apply biochar with different surface treatments in sloping soil to first adsorp and fix non-point source pollutants such as nitrate or phosphate. In this study, the untreated biochar (CK) was pickled with 0.1 M hydrochloric acid for 1 hour to obtain acid-treated biochar (Acid-treated biochar；ATB), and the iron was co-precipitated by the specific adsorption of phosphate by metal oxides. Iron-coated biochar (Fe-treated biochar；FeTB) was formed on the surface of ATB, and the adsorption efficiency of biochar with different surface treatments on phosphate was investigated when the pH was fixed (pH=7) in different initial concentrations of phosphorus addition solution. Finally, the Langmuir isotherm was used to obtain the maximum adsorption capacity (qm). Our results indicated that the adsorption capacity of the biochar with different surface treatments increased with the increase of initial concentration. As the initial concentration was 500 mg/L, the maximum adsorption capacity of untreated biochar (CK) was 55.5 mg/g, and the acid-washed biochar (ATB) had a maximum adsorption capacity of was 56.8 mg/g, while the adsorption capacity of iron-coated biochar (FeTB) was 327.8 mg/g under the same conditions.In Langmuir isotherm, the adsorption modes of biochars with different surface treatments are consistent with this isotherm adsorption formula, and the correlation coefficient R values are all greater than 0.96, and the maximum adsorption capacity of ATB and FeTB estimated by Langmuir isotherm is 104.9 mg /g and 325.8 mg/g, the former is nearly 50 mg/g different from the actual experimental result, while the latter is close to the actual result. From the Electron Probe Microanalyzer (EPMA), it can be found that after FeTB is adsorbed, the site overlap rate of iron and phosphate is high, while the adsorption site of phosphorus on ATB is mainly in the residual biochar. Metals (magnesium, potassium). It can be seen from the above that FeTB can effectively retain the characteristics of metal oxides on phosphate, and increase the adsorption effect of biochar on phosphate.