富含重金属生物炭的环境风险及潜在应用探讨

发布时间：2018-01-08 22:13

本文关键词：富含重金属生物炭的环境风险及潜在应用探讨　出处：《西北农林科技大学》2017年硕士论文　论文类型：学位论文

更多相关文章： 生物炭 重金属 风险特性 潜在应用

【摘要】：为了研究含有重金属元素生物炭的环境风险特性及潜在应用,本研究选取了含重金属Cu、Zn、Pb和Cd的生物吸附剂废渣、含Zn、Mn元素的干电池废弃物和含Zn药渣作为原材料,以高温热解法制备了不同种类的生物炭,运用SEM-EDX、N2吸附-解吸、XPS、FT-IR以及TEM-SEAD衍射等技术手段,表征分析了不同制备温度对生物炭理化性质和表面空隙结构的影响;并以三酸消解、BCR提取和溶出试验等方法,分析了不同制备温度对生物炭中重金属化学行为的影响,并通过风险评估指数(Risk assessment code,RAC)、米勒地质累积指数(Muller geo-accumulation index,Igeo)以及潜在生态风险指数(Potential ecological risk index,RI)等客观地评价了含重金属生物炭的潜在环境风险;最后,结合不同生物炭的自身特点,对其潜在资源化利用做了初步研究。主要研究结果与结论如下:(1)含重金属的吸附剂废渣经高温(350、550、750℃)炭化后,含Cu、Zn、Pb和Cd生物炭pH由8.49、7.86、7.94和7.96(350℃)显著提高至10.19、10.08、10.98和10.71(750℃),但EC先降后升且变化幅度较小。提高裂解温度,生物炭产率从40%-55%(350℃)显著降低至27%-28%(750℃),灰分产率从28%-30%(350℃)增大至48%-54%(750℃);且C/N比增大,H/C和O/C比降低,表明生物炭芳香性增强。裂解炭化后生物炭孔隙更加发达,含Cu、Zn、Pb和Cd生物炭比表面积分别显著提高至208.41、183.38、230.20和241.33 m2 g-1(750℃),平均孔径从10-40 nm(350℃)减小至6-7 nm(750℃),均为介孔孔径(2-20 nm)。FT-IR分析表明,裂解温度升高使官能类型和总量减少,但金属氧化物化合键明显增多。XPS和TEM-SEAD衍射分析显示,裂解过程使Cu(II)氧化态部分向Cu(I)和Cu(0)晶体转变,而Zn(II)、Pb(II)、Cd(II)氧化态并不存在显著变化。提高裂解温度,生物炭内重金属总量进一步浓缩,且重金属酸溶态与可还原态向可氧化态与残渣态转化;RAC、RI指数均明显减小,重金属稳定性加强,环境风险和潜在生态危害降低;虽然Igeo逐步增大,重金属地质积累性危害增大,但种子发芽指数与平均根长逐渐增大,对植物毒性显著降低。对含重金属的生物炭开展的潜在资源化利用研究表明,含Cu生物炭可降低蓝藻体系的pH并使pH稳定在8~9之间,同时提高EC并稳定在2000-2100μs·cm-1,含Cu炭能够抑制藻类繁殖过程中叶绿素a含量的增加,从而抑制水藻正常的繁殖生长。(2)将不同比例(10%、20%和30%)的电池黑碳粉(负极材料)与锯末混合后,550℃热解处理,使pH由7.44、7.23及7.05(原料)显著提高至10.80、10.94及10.85(复合炭),EC值由1.91、2.53和3.85(mS·cm-1)(原料)显著降低至1.67、2.08和2.30(mS·cm-1)(复合炭),灰分产率由54.76、64.10、70.28%(原料)降低至21.34、29.89、37.26%(复合炭)。热解处理后物质的C和N含量均降低,但电池黑碳粉添加比例对复合炭的C/N比影响较小;随着电池黑碳添加比例的增加,复合炭的比表面积从61.23 m2 g-1(10%-C)降低到37.27 m2 g-1(30%-C),而平均孔径从7.13 nm增大到12.65 nm。复合炭中重金属Mn、Zn含量较高,且与添加比例呈显著性正相关关系。复合炭的溶出试验表明,强酸环境下,Mn、Zn元素有较大的溶出风险。复合炭的生态毒性试验表明,复合炭的种子发芽指数与平均根长明显小于空白,说明了复合炭具有一定的生态毒性。锯末-电池复合炭中BBC550-30%具有较良好的吸附性能。在pH 5.0,400 mg·L-1Pb(II)溶液,50℃等外界条件下吸附量最高,达到124.64 mg·g-1。Pb(II)的吸附机制主要为表面吸附、孔内扩散静电吸引和表面沉淀吸附过程。(3)550℃裂解药渣后,获得的药渣炭pH显著升高至9.85,EC降低至1.82(mS·cm-1),灰分产率下降了6.5%,碳含量减少了28.8%,氮含量减少了44.0%,C/N比降低了21.2%。药渣炭中Zn明显浓缩,RAC、RI值显著减少,生物有效性、环境风险和潜在生态风险显著减小。含Zn药渣炭对植物生长具有一定的毒害性,但随着生物炭裂解温度提高,重金属毒害性明显降低。但小青菜盆栽试验表明,由于浓缩大量重金属Zn元素,含Zn生物炭进入土壤环境后会导致小青菜体内Zn积累显著,因而其应用的毒害性需要进一步的研究探讨。
[Abstract]:In order to study the environmental risk characteristics of heavy metal elements containing biochar and potential applications, this study selected the containing heavy metals of Cu, Cd and Pb Zn, biosorbent waste residue, containing Zn, Mn elements and Zn containing waste dry battery dregs as raw materials, which were prepared by pyrolysis of biochar, different the use of SEM-EDX, N2 adsorption desorption, XPS, FT-IR and TEM-SEAD diffraction techniques, characterization of different preparation temperature effects on physicochemical properties and surface pore structure of biochar; and by acid digestion, and dissolution test method of BCR extraction, analysis of different preparation temperature influence on the chemical behavior of heavy metals biochar, and through the risk assessment index (Risk assessment, code, RAC), Miller (Muller geo-accumulation index geoaccumulation index, Igeo) and the potential ecological risk index (Potential ecological risk index, RI) objective assessment The price of the heavy metal containing biochar potential environmental risk; finally, the combination of different biochar characteristics, the potential resource utilization were studied. The main results and conclusions are as follows: (1) adsorbent waste containing heavy metals by high temperature (350550750 DEG C) after carbonization, containing Cu, Zn, and Pb Cd 8.49,7.86,7.94 and 7.96 pH by biochar (350 C) increased to 10.19,10.08,10.98 and 10.71 (750 C), but EC decreased and then increased and the amplitude of variation is small. Increasing the pyrolysis temperature, biochar yield from 40%-55% (350 DEG C) was reduced to 27%-28% (750 DEG C), ash yield from 28%-30% (350 C) increased to 48%-54% (750 DEG C); and the C/N ratio increased, H/C and O/C are lower than that of biological carbon aromaticity increased. After carbonization pyrolysis biochar pore is more developed, including Cu, Zn, Pb and Cd bio carbon surface area were significantly increased to 208.41183.38230.20 and 241.33 M2 g-1 (750 C), average pore Size from 10-40 nm (350 DEG C) reduced to 6-7 nm (750 C), both pore size (2-20 nm).FT-IR analysis showed that pyrolysis temperature increased functional types and reduce the amount of metal oxide, but chemical bonds increased significantly.XPS and TEM-SEAD diffraction analysis showed that the pyrolysis process of the Cu (II) oxidized part to Cu (I) and Cu (0) crystal transformation, and Zn (II), Pb (II), Cd (II) oxidation state does not exist significant changes. To improve the cracking temperature of biochar in the total amount of heavy metals and heavy metals enriched, acid soluble and reducible to the oxidation state and residue can be transformed state; RAC, RI index were significantly decreased, the stability of heavy metals to strengthen environmental risk and potential ecological risk is reduced; while Igeo increased gradually, the heavy metal accumulation of geological hazard increases, but the seed germination index and average root length increased, toxicity to plants decreased significantly. The potential resources of biological carbon containing heavy metals is carried out The study shows that Cu containing biochar can reduce cyanobacteria system pH and make pH stable between 8~9 and EC and improve the stability in the 2000-2100 s cm-1, Cu containing carbon can increase the chlorophyll content of a inhibiting algae breeding process, thereby inhibiting the normal growth and reproduction of algae. (2) the different proportion (10%, 20% and 30%) of the battery (black carbon anode materials) and sawdust mixture, 550 C pyrolysis process, the pH by 7.44,7.23 and 7.05 (raw material) significantly increased to 10.80,10.94 and 10.85, EC (composite carbon) from 1.91,2.53 (mS - cm-1) and 3.85 (raw material) significantly reduced to 1.67,2.08 and 2.30 (mS - cm-1) (composite carbon) and ash yield by 54.76,64.10,70.28% (raw material) is reduced to 21.34,29.89,37.26% (composite carbon). Pyrolysis material C and N were lower, but the battery of black powder addition on the composite carbon C/N was smaller than the influence; with the increase of the proportion of added carbon black battery, composite Carbonspecific from 61.23 M2 g-1 (10%-C) reduced to 37.27 M2 g-1 (30%-C), and the average pore size increases from 7.13 nm to 12.65 nm. heavy metal composite carbon Mn, higher Zn content, and was significantly positively correlated with the proportion of added. Composite carbon dissolution test showed that the strong acid environment Mn, Zn, dissolved elements have greater risk. The test results showed that the ecological toxicity of composite carbon carbon composite, the seed germination index and the average root length was significantly less than the blank, the composite carbon has a certain eco toxicity. Sawdust - battery carbon composite BBC550-30% has good adsorption properties in pH 5.0400 mg. L-1Pb (II) solution, 50 degrees outside under the condition of adsorption was the highest, reached 124.64 Mg - g-1.Pb (II) adsorption mechanism is mainly surface adsorption, pore diffusion electrostatic attraction and surface precipitation adsorption process. (3) 550 C cracking residue, the residue carbon pH significantly increased to 9.85. EC Reduced to 1.82 (mS - cm-1), ash yield decreased by 6.5%, the carbon content decreased by 28.8%, nitrogen content decreased by 44%, C/N decreased the 21.2%. residue carbon Zn was concentrated, RAC, RI were significantly reduced, bioavailability, reduce environmental risk and potential ecological risk. The residue containing Zn carbon has toxicity to plant growth, but with biochar pyrolysis temperature increased, the toxicity of heavy metals decreased. But the cabbage pot experiment showed that the concentration of heavy metal elements as Zn, Zn containing biochar into soil environment will lead to small cabbage Zn accumulation significantly, so the application of toxic need further discussion the study.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ424;X13

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