利用奈米鎳/鋅磁氧鐵礦處理含硝酸鹽/亞硝酸鹽廢水之研究

Degradation of Nitrate/Nitrite in Wastewater over Nickel or Zinc Ferrite Nanoparticles

楊政霖(Cheng-Ling Yang)

指導教授 ： 林錕松

元智大學/工程學院/化學工程與材料科學學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00296

摘要

近年來，臺灣地區因科技發達導致廢水污染問題日趨嚴重，因此，本論文之研究目的是合成鎳/鋅磁氧鐵礦(Ni, Zn-Fe2O4)後，用來還原硝酸鹽/亞硝酸鹽水溶液。本研究流程可分為鎳/鋅磁氧鐵礦之合成、應用、再生及回收再使用四個部份，並深入探討鎳/鋅磁氧鐵礦之結構特性，及瞭解其對硝酸鹽、亞硝酸鹽或不同實廠廢水之處理效果。再以擬一階反應動力模式求得反應動力參數。
實驗部份以操作條件在pH = 8.5、轉速1250 rpm及453 K下，以水熱法合成Ni, Zn-Fe2O4，分別以穿透式電子顯微鏡(TEM)、場發掃描式電子顯微鏡(FE-SEM/EDS)、氮氣吸附孔隙儀(ASAP)及奈米級微粒粒徑分析儀(Coulter N4 Plus)進行比表面積、孔洞及粒徑分析；X光粉末繞射儀(XRPD)、傅立葉轉換紅外線光譜儀(FTIR)、化學分析電子光譜儀(ESCA)及同步輻射吸收光譜(XANES/EXAFS)進行結構及性質分析，藉由XRPD測試後與資料庫標準品比對後得知2θ = 35.66及35.24分別出現NiFe2O4與ZnFe2O4訊號，證實其為具有尖晶石結構之Ni, Zn-Fe2O4。經由TEM、FE-SEM、ASAP及Coulter N4 plus分析得知Ni, Zn-Fe2O4結構完整且分佈均勻，粒徑大小約為50~100 nm。由ASAP之吸/脫附曲線及孔徑分佈情形可知其為中孔洞型態之Ni, Zn-Fe2O4，ZnFe2O4之比表面積(170.7 m2/g)略大於NiFe2O4 (100.4 m2/g)。由EDS分析得知所合成Ni, Zn-Fe2O4偵測到之訊號分別為Ni、Fe、O與Zn、Fe、O，可確定其分別為Ni, Zn-Fe2O4。經FTIR分析後可知Ni, Zn-Fe2O4官能基特性吸收峰位置分別在571及593 cm-1，確定其為Ni, Zn-Fe2O4結構。經由ESCA分析後得知NiFe2O4中Fe(2p)之化學位移為711.05 eV，可得知其為Fe(III)；Ni(2p)之化學位移為855.3 eV，判定其為Ni(II)之NiFe2O4。而ZnFe2O4中Fe(2p)之化學位移為711.25 eV，可得知其為Fe(III)；而Zn(4配位)及Zn(6配位)之化學位移分別為1021.95及1023.08 eV，因具4配位之Zn(II)的面積佔有百分率大於具6配位之Zn(II)，得知所合成之Ni, Zn-Fe2O4為逆尖晶石結構。
由XANES/EXAFS分析後得知，經氫氣還原後會導致Ni, Zn-Fe2O4結構因產生氧空缺使其pre-edge吸收峰較Fe3O4往前偏移2 eV，EXAFS結果顯示氫化前Ni, Zn-Fe2O4第一層Fe-O之鍵長分別為1.95及1.94 Å；其配位數分別為4.03及3.81，而氫化後Ni, Zn-Fe2O4第一層Fe-O之鍵長分別為1.98及2.03 Å；其配位數分別為3.83及2.85，由其結構參數變化證實第一層Fe-O結構會因氧空缺而產生鍵長變長及配位數減少之情形。因此，可將Ni, Zn-Fe2O4於573 K下進行氫氣活化2 h，使其產生氧空缺進而應用於處理不同濃度之硝酸鹽/亞硝酸鹽水溶液。經由UV/Vis分析結果顯示，於最佳操作條件(pH = 5、水溫25℃及反應時間240 min)下之反應過程可視為擬一階反應且其反應速率常數(k)值會隨著處理前之原廢水濃度的減少而增加；ZnFe2O4還原硝酸鹽或亞硝酸鹽之效果略優於NiFe2O4。在處理不同實廠廢水之實驗結果中可知其去除率依序為ZnFe2O4 > NiFe2O4。
經XRPD、TEM及FE-SEM分析顯示，Ni, Zn-Fe2O4於反應前/後之結構穩定，再利用外加磁場方式進行回收後，得知其Ni, Zn-Fe2O4之回收率分別為98.25及98.36%，故深具回收再使用之潛力。因此，本論文研究之成果，可以有效減少硝酸鹽/亞硝酸鹽污染問題，並能進一步應用於工業廢水處理技術之提升。

關鍵字

奈米鎳/鋅磁氧鐵礦微粒 ； 水熱合成法 ； 硝酸鹽 ； 亞硝酸鹽 ； 催化分解 ； 同步輻射吸收光譜

並列摘要

Recent advance in technology has led to serious wasterwater pollution in Taiwan. As a result, many nitrate/nitrite wastewater treatment technologis has been evolved eventually. Therefore, the main objective of this research was to synthesize the nickel (Ni) or zinc (Zn) ferrites (Ni- or Zn-Fe2O4) and to reduce the concentration of nitrate/nitrite contaminants in wastewaters. The current research can be divided into four sections including synthesis of ferrites, application of ferrites on nitrate/nitrite contaminants removal, regeneration, and recycle or reuse of ferrite nanoparticles. Moreover, the kinetic parameters got by pseudo-first-order model equation were also found.
Experimentally, nickel or zinc ferrite nanoparticles were synthesized under hydrothermal conditions (pH = 8.5, T = 453 K, and mixing rate of 1250 rpm) by precipitating from metal nitrates with aqueous ammonia. Synthesized nanopowders were characterized by X-ray powder diffractometer (XRPD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), BET surface area and porosimeter, electron spectroscopy for chemical analysis (ESCA), Fourier transform infrared spectrometer (FTIR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), ultraviolet-visible spectrophotometer (UV/Vis), and particle size meter. These results showed that the pore sizes of Ni, Zn-Fe2O4 were about 50-100 nm with spinal structure. Ni, Zn-Fe2O4 having strong characteristic peaks at 2θ = 35.66 and 35.24 were investigated by XRPD patterns, respectively. The specific surface area of Ni, Zn-Fe2O4 measured by ASAP isotherms were 100.4 and 170.7 m2/g, respectively. From ESCA spectra, the results showed that the Fe(2p) of Ni, Zn-Fe2O4 were at 711.05 and 711.25 eV respectively, Ni(2p) of NiFe2O4 were at 855.3 eV, Zn(2p) of ZnFe2O4 were at Zn(4) = 1021.95 eV, and Zn(6) = 1023.08 eV, respectively. By using FTIR spectra, the results showed that the characteristic peaks of Ni, Zn-Fe2O4 were about at 571 and 593 cm-1, respectively, the O-H characteristic peaks of Ni, Zn-Fe2O4 were at 1382 and 1380 cm-1, respectively.
The XANES/EXAFS spectra showed that the valencies of the Ni, Zn-Fe2O4 were Ni(II) and Zn(II), respectively. The first shell of Fe-O bonding for Ni, Zn-Fe2O4 with bond distances were 1.95 and 1.94 Å and coordination numbers of 4.03 and 3.81, respectively before hydrogen reduction. Similarly, the first shell of Fe-O bonding for Ni, Zn-Fe2O4 with bond distances were 1.98 and 2.03 Å and coordination numbers of 4.03 and 3.81 respectively after hydrogen reduction at 573 K and 1 atm. The decomposition of nitrate or nitrite contaminants analyzed by UV/Vis was investigated by oxygen-deficient Ni, Zn-Fe2O4 formed by hydrogen reduction at 573 K and 1 atm. As indicated by the results from XRPD, TEM and FE-SEM, the fine structure of Ni, Zn-Fe2O4 did not change after the reaction. In terms of nitrate and nitrite wastewater treatment, the decomposition rates of Zn-ferrites were more efficient than the ones of Ni-ferrites at optimum operating condition at pH = 5 in room temperature. Reaction process described by pseudo-first-order model equation and the k value was increased while the wastewater concentration decreased. The optimized operating conditions were also applied on wasterwater treatment plants, it was found that Zn-ferrites were more efficient than the ones of Ni-ferrite nanoparticles.
As shown by XRPD, TEM and FE-SEM analyses, the structure of Ni, Zn-Fe2O4 is very stable and can be recycled. The recyclibility rates of Ni, Zn-Fe2O4 were 98.25 and 98.36% repectively. Thus, the outcome of this study would be able to be applied on existing wasterwater treatment so as to improve the efficiencies of the processes.

並列關鍵字

Nickel and zinc ferrite nanoparticle ； Hydrothermal method ； Nitrate ； Nitrite ； Catalytic decomposition ； XANES/EXAFS

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