發(fā)布時(shí)間：2018-05-02 08:05

  本文選題：對(duì)苯醌 + 弱酸　； 參考：《遼寧大學(xué)》2017年碩士論文

【摘要】：隨著全球經(jīng)濟(jì)發(fā)展進(jìn)入新常態(tài),人類向自然界索取的越來(lái)越多,由之而產(chǎn)生的環(huán)境問(wèn)題也越來(lái)越多,其中以空氣污染與水體污染最為嚴(yán)重。人類迫切需要一種能夠快速檢測(cè)空氣及水體中污染物的方法,本論文建立了一種快速有效地檢測(cè)空氣中甲醛含量及水體中銨鹽含量的新方法。具體方法是利用電化學(xué)方法,通過(guò)對(duì)比對(duì)苯醌(Q)還原過(guò)程中,銨鹽和甲醛反應(yīng)所生成酸提供質(zhì)子,產(chǎn)生新峰的峰電流高度來(lái)檢測(cè)銨鹽和甲醛含量。實(shí)驗(yàn)中由于甲醛和NH4+酸性都非常弱,不能釋放足夠的質(zhì)子來(lái)抑制電極界面pH的升高,所以我們通過(guò)銨鹽與甲醛作用(甲醛法)定量生成相對(duì)較強(qiáng)的酸,從而抑制電極表面pH的上升,產(chǎn)生新的差分脈沖峰,該峰不受對(duì)苯醌、銨鹽和甲醛濃度的影響,只隨生成酸濃度的增加而升高,這樣可以更快更準(zhǔn)確的測(cè)定其含量。根據(jù)實(shí)際實(shí)驗(yàn)情況我們首先采用循環(huán)伏安法驗(yàn)證此方法的可行性,接下來(lái)用差分脈沖法進(jìn)行測(cè)定。由實(shí)驗(yàn)結(jié)論可知,當(dāng)水溶液中有質(zhì)子存在時(shí),對(duì)苯醌在水溶液中還原時(shí)首先接受游離態(tài)的質(zhì)子,反之對(duì)苯二酚在氧化時(shí)會(huì)釋放質(zhì)子。在非緩沖的水溶液中,它們的氧化還原結(jié)果會(huì)使電極表面的pH值升高或降低。酸釋放的質(zhì)子會(huì)導(dǎo)致在相對(duì)較正的電位上產(chǎn)生新的還原峰。此外,不同pKa的酸,由于其釋放質(zhì)子的能力不同,從而導(dǎo)致新峰的出峰電位也不同,所以可以根據(jù)酸的出峰電位來(lái)判斷物質(zhì)的酸性強(qiáng)弱。因在中性條件下,乙酸銨和甲醛均不能提供質(zhì)子導(dǎo)致新峰的產(chǎn)生,所以我們利用甲醛法作用的產(chǎn)物—較強(qiáng)酸為對(duì)苯醌還原提供質(zhì)子。本論文根據(jù)以上原理,通過(guò)測(cè)定水溶液中生成酸含量從而定量測(cè)定了銨鹽及甲醛含量。由實(shí)驗(yàn)數(shù)據(jù)可知,生成酸濃度決定對(duì)應(yīng)較正電位的峰電流值,我們可以根據(jù)酸濃度與峰電流繪制標(biāo)準(zhǔn)曲線,從而可得出銨鹽和甲醛的濃度,我們還可以用此方法來(lái)測(cè)定未知樣品中NH4+和甲醛的含量。以上測(cè)定方法較傳統(tǒng)的測(cè)試方法不僅靈敏度提高了,且不需復(fù)雜的預(yù)處理,為實(shí)際的電化學(xué)測(cè)定銨鹽和甲醛提供了一個(gè)新途徑。
[Abstract]:With the development of global economy entering into the new normal, more and more human beings demand from nature, and more and more environmental problems arise from it, among which air pollution and water pollution are the most serious. There is an urgent need for a rapid method to detect pollutants in air and water. In this paper, a new method is established to detect formaldehyde in air and ammonium salt in water. The specific method is to detect the content of ammonium salt and formaldehyde by comparing the acid produced by the reaction of ammonium salt with formaldehyde and the peak current height of the new peak in the process of p-benzoquinone Q) reduction by electrochemical method. Because the acidity of formaldehyde and NH4 is so weak that we can not release enough protons to restrain the increase of pH at the electrode interface, so we quantitatively produce relatively strong acids by the interaction of ammonium salt with formaldehyde (formaldehyde method). Therefore, the increase of pH on the electrode surface is inhibited and a new differential pulse peak is produced. The peak is not affected by the concentration of p-benzoquinone, ammonium salt and formaldehyde, but only increases with the increase of the concentration of the formed acid, which can be measured more quickly and accurately. According to the actual experimental conditions, we first use cyclic voltammetry to verify the feasibility of this method, and then use differential pulse method to determine. The experimental results show that when protons exist in aqueous solution, p-benzoquinone first receives protons in the free state when it is reduced in aqueous solution, whereas hydroquinone releases protons when it is oxidized. In non-buffer aqueous solutions, their redox results increase or decrease the pH value of the electrode surface. Protons released by acids cause new peaks of reduction at relatively positive potentials. In addition, due to the different proton release ability of different pKa acids, the peak potential of the new peak is also different, so the acidity can be judged according to the acid peak potential. Under neutral conditions, ammonium acetate and formaldehyde can not provide protons to lead to new peaks, so we use the product of formaldehyde method-strong acid to provide proton for p-benzoquinone reduction. According to the above principle, the content of ammonium salt and formaldehyde in aqueous solution was determined quantitatively by the determination of the acid content in aqueous solution. According to the experimental data, we can draw the standard curve according to the acid concentration and peak current to determine the peak current value corresponding to the positive potential, and then we can get the concentration of ammonium salt and formaldehyde. We can also use this method to determine the content of NH4 and formaldehyde in unknown samples. The above methods not only improve the sensitivity, but also do not require complex pretreatment, which provides a new way for the electrochemical determination of ammonium salt and formaldehyde.
【學(xué)位授予單位】：遼寧大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X830;O657.1

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本文編號(hào)：1833075