農業廢棄物所合成的碳屬吸附劑在污染水稻土中固定鎘之應用;Application of carbonaceous adsorbents derived from agricultural wastes in immobilization of cadmium in contaminated paddy soil

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题名:	農業廢棄物所合成的碳屬吸附劑在污染水稻土中固定鎘之應用;Application of carbonaceous adsorbents derived from agricultural wastes in immobilization of cadmium in contaminated paddy soil
作者:	黃氏美惠;Hue, Huynh Thi My
贡献者:	環境工程研究所
关键词:	鎘;炭屬吸附劑;農業廢棄物;模式;現地穩定化;水田土壤;Cadmium;carbonaceous sorbents;agricultural wastes;modeling;in situ immobilization;paddy soil
日期:	2019-11-05
上传时间:	2020-01-07 14:39:46 (UTC+8)
出版者:	國立中央大學
摘要:	本論文的研究目的旨在評估使用源自農業廢物(包括樟樹樹葉和玉米芯)的碳基吸附劑將鎘固定在受污染水稻田土壤中的可行性。具體而言，論文的內容包括：(1)利用此兩種原料合成包括活性炭、生物炭和水熱炭等三種類型的含碳吸附劑後，表徵它們的表面與形態特性；(2)將所合成的吸附劑進行水相環境中的鎘吸附試驗，以比較各吸附劑對鎘的吸附能力，並得知吸附機制；(3)藉由土壤培養確定水田土壤於厭氧狀態下對於鎘的穩定效應，以及驗證從水相鎘等溫吸附所得的平衡分佈模型的預測能力。當吸附試驗以稻田土壤孔隙水pH值的條件下(即pH 6.5)進行時，所觀察到的吸附動力和平衡數據可分別以擬二階模式與Langmuir模式得到最佳的擬合結果；若從中比較各吸附劑的鎘吸附能力可知：以樟樹樹葉合成的吸附劑中，活性炭在去離子水環境展現最高的鎘離子吸附量(Qmax = 13.33 mg g-1)，生物炭則是在孔隙水基質表現出最佳的吸附效果(Qmax = 8.48 mg g-1)，而就玉米芯吸附劑而言，無論在去離子水還是在孔隙水基質中，活性炭均表現出最高的鎘吸附能力；如將此結果與吸附劑的表徵測量結合時，可知表面積、孔體積和表面上含氧官能團的多寡與種類似乎影響吸附劑與鎘之間吸附相互作用中較為關鍵的因素；最後，儘管線性模型的預測沒有被土壤培養結果完全證實，但從培養中觀察到的各吸附劑對於鎘在土壤固定化趨勢與模型所預測的完全一致。綜合而言，這些結果表明對於許多環境應用，尤其是針對現地金屬的固定化而言，生物炭和水炭可能是相對有效且低成本和環保的炭屬吸附劑。;The objective of this study was to assess the feasibility of using carbon-based adsorbents derived from agricultural wastes including camphor tree leaves and corncobs to immobilize cadmium (Cd) in a contaminated rice paddy. Specifically, (1) three types of carbonaceous sorbents including activated carbons, biochars and hydrothermal chars (or hydrochars) were synthesized from these two feedstocks and characterized with the surface and morphological properties of each one; (2) followed by aqueous Cd-adsorption experiments of individual synthetic sorbent under various conditions in order to not only compare the adsorption capacity but also acquire the adsorption mechanisms; and (3) lastly by soil incubation tests to both validate the predicting power of the linear equilibrium distribution model acquired from aqueous isotherms and ensure the Cd-sequestering effect of sorbents in anaerobic paddy soil. Under a pH condition that was representative of the pore water pH detected in the paddy soil (i.e., pH 6.5), data of sorption kinetic and equilibrium experiments carried out at both high and low levels of Cd were found to be better explained by the pseudo-second-order model and the Langmuir isotherm, respectively. Of the leaf sorbents, activated carbon showed the highest Cd2+ sorption capacity in DI water (Qmax= 13.33 mg g-1), whereas biochar displayed the best effectiveness in porewater (Qmax =8.48 mg g-1); as for the corncob sorbents, activated carbon exhibited the highest capacity of Cd adsorption no matter in the DI or porewater matrix. When combined with the characterization measurements, surface area, pore volume, and oxygen-containing functional groups on the surface were the factors that seemed to play more significant roles in the adsorptive interaction between ionic Cd and the sorbent. Finally, although the prediction of the linear model was not completely validated by the soil incubation results, the immobilization trend observed from the incubations was fully consistent to the model. Together, findings of this work suggest that biochars and hydrochars could be relatively effective, low-cost, and eco-friendly sorbents for many environmental applications, particularly concerning in situ metal immobilization.
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