發(fā)布時(shí)間：2019-04-23 14:07

【摘要】：鎘是一種重金屬，可以致癌。如果在環(huán)境中通過飲用水或者食物鏈進(jìn)入人體將對(duì)人類造成很大的危險(xiǎn)。所以在工業(yè)上或者水源里對(duì)鎘的去除至關(guān)重要。本文用電沉積法和混凝法組合工藝處理高濃度的含鎘廢水，在回收鎘金屬的同時(shí)，使處理后水體的鎘濃度達(dá)到《污水綜合排放標(biāo)準(zhǔn)》(GB8978-1996)規(guī)定的0.1mg/L排放標(biāo)準(zhǔn)。 在電沉積過程中，利用電沉積的方法回收將廢水中的鎘，，實(shí)驗(yàn)中在電解槽內(nèi)采用多陰陽極反應(yīng)器內(nèi)分別考察不同初始濃度的含鎘廢水（400mg/L、600mg/L、1000mg/L）、不同初始pH（1.5、3.5、5.5、7.5）、不同電流密度（1.49mA/cm2、2.97mA/cm2、4.46mA/cm2、5.95mA/cm2）、不同電解質(zhì)種類及濃度（NaCl、NaNO3、Na2SO4）、不同腐殖酸濃度和絡(luò)合物對(duì)電沉積含鎘廢水的影響。實(shí)驗(yàn)結(jié)果表明在工作電極為鈦板的三相電極中，鎘的還原電位為-0.64V到-0.78V。一級(jí)動(dòng)力學(xué)常數(shù)和電流效率隨著鎘的初始濃度的增加而增加。當(dāng)電流密度從1.49mA/cm2增到4.46mA/cm2時(shí),在120分鐘電沉積時(shí)間內(nèi)，鎘的回收率從96.98%上升到99.3%，此時(shí)再增加電流密度，鎘的回收效率和電流效率都不會(huì)再增加。當(dāng)溶液中存在硝酸鈉電解質(zhì)時(shí)，會(huì)使鎘的反應(yīng)速率下降。當(dāng)溶液中存在腐殖酸的濃度為200mg/L時(shí)，在前60分鐘，鎘的反應(yīng)速率很慢，但是隨著腐殖酸被氧化，在后60分鐘，反應(yīng)速率則加快。氨水的存在會(huì)促進(jìn)電沉積鎘的反應(yīng)速率。通過采用掃描電鏡和能譜、X射線衍射儀和X射線光電子能譜儀對(duì)沉積物進(jìn)行分析發(fā)現(xiàn)：在電沉積過程中，廢水中的主要以單質(zhì)鎘和氫氧化鎘的形式被沉淀。 在混凝沉淀階段，研究不同pH值（5.0、6.0、7.0、8.0、9、0）、不同Al存在形式的絮凝劑和不同投加量對(duì)鎘去除效果的影響。實(shí)驗(yàn)結(jié)果表明初始pH為9的溶液，鎘的去除效果較好。以Al存在形式的高聚物比低聚物和中聚物去除鎘效果很好。當(dāng)隨著聚合氯化鋁（PAC）投加量增加，當(dāng)PAC投加量大于0.4mL，溶液中的鎘去除率高達(dá)90%，說明只要投加少量的PAC，就可以起到很好的混凝效果。當(dāng)隨著聚合氯化鋁（PAC）投加量增加，Al的存在形式以高聚物為主，鎘的去除效果明顯增加。對(duì)絮體進(jìn)行XRD表征發(fā)現(xiàn)絮體主要以碳酸鎘和氫氧化鎘的形式存在。
[Abstract]:Cadmium is a heavy metal that can cause cancer. If you enter the human body through drinking water or food chain in the environment, it will be a great danger to human beings. Therefore, the removal of cadmium in industry or in water sources is essential. In this paper, the combined process of electrodeposition and coagulation is used to treat the wastewater containing high concentration of cadmium. While recovering cadmium metal, the concentration of cadmium in the treated water reaches the 0.1mg/L discharge standard stipulated in the Integrated Wastewater discharge Standard (GB8978-1996). In the process of electrodeposition, cadmium in the wastewater was recovered by electrodeposition. In the experiment, the cadmium-containing wastewater with different initial concentrations (400 mg / L, 600 mg / L, 1000 mg / L) was investigated in a multi-cathode and anode reactor in an electrolytic cell. Different initial pH (1.5, 3.5, 5.5, 7.5), different current densities (1.49 Ma / cm 2, 2.97 Ma / cm 2, 4.46 Ma / cm 2, 5.95 Ma / cm 2), different electrolyte types and concentrations (NaCl,NaNO3,Na2SO4), Effect of humic acid concentration and complex on electrodeposition of cadmium-containing wastewater. The experimental results show that the reduction potential of cadmium is-0.64 V to-0.78 V. in the three-phase electrode with titanium plate as the working electrode. The first order kinetic constant and current efficiency increase with the increase of initial concentration of cadmium. When the current density increases from 1.49mA/cm2 to 4.46mA/cm2, the recovery rate of cadmium increases from 96.98% to 99.3% in 120min electrodeposition time. When the current density is increased, the recovery efficiency and current efficiency of cadmium will not increase any more. When sodium nitrate electrolyte exists in the solution, the reaction rate of cadmium will decrease. When the concentration of humic acid in the solution is 200mg/L, the reaction rate of cadmium is very slow in the first 60 minutes, but increases with the oxidation of humic acid in the last 60 minutes. The presence of ammonia can promote the rate of electrodeposition of cadmium. By means of scanning electron microscopy and energy spectrum, X-ray diffractometer and X-ray photoelectron spectroscopy, it is found that in the process of electrodeposition, the waste water is mainly precipitated in the form of cadmium hydroxide and cadmium hydroxide. The effects of different pH values (5.0, 6.0, 7.0, 8.0, 9, 0), different forms of flocculants in the presence of Al and different dosages on the removal of cadmium were studied in the coagulation and sedimentation stage. The effects of different pH values (5.0, 6.0, 7.0, 8.0, 9, 0) on the removal of cadmium were studied. The experimental results show that the removal effect of cadmium is better when the initial pH is 9. The removal of cadmium by polymer in the form of Al is better than that of oligomer and polymer. When the dosage of polyaluminum chloride (PAC) increases, when the dosage of PAC is more than 0.4 mL, the removal rate of cadmium in the solution is as high as 90%, indicating that the coagulation effect can be achieved by adding a small amount of PAC,. With the increase of the dosage of polyaluminum chloride (PAC), the existence of Al was mainly in the form of polymer, and the removal efficiency of cadmium was obviously increased. The floc was characterized by XRD. It was found that the floc was mainly in the form of cadmium carbonate and cadmium hydroxide.
【學(xué)位授予單位】：南華大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：X703.1;TQ150

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