【作者】 胡婷婷；

【导师】 周长春；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2020， 硕士

【摘要】 针对目前工业废水中含有大量重金属离子的处理需求,本文以Hg²⁺为吸附对象,研究了粉煤灰基介孔硅铝吸附材料的制备及其对水中Hg²⁺的吸附性能。粉煤灰为燃煤固体残渣,每年数以亿吨的产生导致占用了大量的土地资源,另外一方面粉煤灰中含有大量的硅铝氧化物和其他有价金属包括稀土元素。因此,无论是从环境保护的角度还是从资源回收再利用的角度,合理的处置粉煤灰势在必行。本文以粉煤灰为研究对象,通过碱熔联合超声处理粉煤灰制备介孔硅铝吸附材料用于处理含汞废水,并以现代分析仪器联用揭示了吸附机理,结合静态吸附试验探究了吸附材料的吸附特性。与中温Na₂CO₃碱熔相比,低温NaOH碱熔预处理粉煤灰得到的碱熔残渣去除水溶液中Hg²⁺的效果更佳。Na₂CO₃碱熔剂与粉煤灰反应温度为860℃,碱熔残渣为无定形硅铝酸盐和结晶产物（Na₂O）_0.33NaAlSiO₄,表面积为11.19 m²/g。而NaOH碱熔试剂与粉煤灰的反应温度为350℃,碱熔残渣为无定形硅铝酸盐和结晶产物羟基方钠石[Na₈Al₆Si6O₂₄·（OH）₂（H₂O）]以及为未熔融的莫来石,比表面积为41.64 m²/g。考察了NaOH碱熔温度、NaOH与粉煤灰配比、碱熔时间、超声强度、超声温度和超声时间对制备介孔硅铝吸附材料去除水溶液中Hg²⁺效果的影响,确定适宜的制备条件为:NaOH碱熔温度350℃,NaOH/粉煤灰为1/1.2,碱熔时间60min,超声强度35 kHz,超声温度50℃和超声时间60 min。制得的介孔硅铝吸附剂材料孔隙主要介于2-25 nm之间,占总孔容的89.627%,是典型的介孔材料,同时BET比表面积达66.858 m²/g,相较于粉煤灰比表面积增大了12倍,孔容扩大7倍。通过SEM和BET分析了超声辅助过程的作用机制,超声不仅将吸附效果较好的吸附材料同实心硅氧产物分开,而且该过程对吸附材料的孔隙具有较好的改善作用。通过FTIR分析可知,超声作用暴露了包裹在硅氧产物中的未燃碳,这也提高了吸附材料的吸附性能。介孔硅铝吸附材料的吸附过程不受表面电性的影响,而是取决于介孔硅铝材料本身性质;吸附量与吸附材料投加量成正比;吸附过程随着吸附时间的延长会有一个饱和吸附时间,再增加吸附时间吸附量不会再有较大变化;循环次数实验表明,介孔硅铝吸附材料的循环性能较好,5次循环实验后吸附性能基本不变。通过吸附方程分析得知,Langmuir吸附等温方程、Freundlich吸附等温方程和Temkin吸附等温方程的相关度分别为0.9975、0.9514、0.9910,三者均具有较好相关性,拟合效果的顺序为Langmuir>Temkin>Freundlich,介孔硅铝吸附材料对Hg²⁺的吸附符合Langmuir方程。吸附过程为单分子层化学吸附,对Hg²⁺最大吸附量达7.937 mg/g,原始粉煤灰对汞离子的吸附量为0.18 mg/g。通过吸附材料的热力学研究,介孔硅铝吸附材料对Hg²⁺的吸附不仅受内扩散过程控制,还受吸附位活性位点控制。介孔硅铝吸附材料中羟基方钠石具有较强的离子交换性能,因此吸附过程为羟基方钠石中钠离子和汞离子交换作用,以及硅铝活性位点与汞离子的交换。该论文有图35幅,表7个,参考文献88篇。更多还原

【Abstract】 In view of the treatment demand of heavy metals ion in industrial wastewater at present,Hg²⁺was taken as the adsorption object in this paper,and the adsorption performance of mesoporous Si-Al adsorption material prepared from fly ash to Hg²⁺was studied.Fly ash is the solid residue of coal combustion,which is produced by hundreds of millions of tons of fly ash every year,occupying a lot of land resources.On the other hand,fly ash contains a lot of silicon oxide and other valuable metals and even rare earth elements.Therefore,whether from the perspective of environmental protection or from the perspective of resource recycling,it is imperative to dispose of fly ash reasonably.In this paper,the mesoporous Si-Al adsorption material was prepared by alkali fusion combined with ultrasonic treatment for the treatment of mercury containing wastewater.The synthesis mechanism was revealed through the combination of adsorption mechanism,and the adsorption characteristics of the adsorbent materials are analyzed by adsorption experiments.Compared with the medium temperature Na₂CO₃ alkali fusion,the effect of removing Hg²⁺from the aqueous solution by the alkali fusion product from the fly ash pretreated by low temperature NaOH alkali fusion is better.The reaction temperature of Na₂CO₃ alkali flux and fly ash is 860℃,the main products of alkali fusion are amorphous aluminosilicate and crystalline product（Na₂O）_0.33NaAlSiO₄,with a surface area of 11.19 m²/g.The reaction temperature of NaOH alkali fusion reagent and fly ash is 350℃,and the products of alkali fusion are amorphous aluminosilicate,crystal product hydroxysodalite[Na₈Al₆Si6O₂₄·（OH）₂（H₂O）]and unmelted mullite,with specific surface area of 41.64 m²/g.The effects of NaOH alkali melting temperature,ratio of NaOH to fly ash,alkali melting time,ultrasonic intensity,ultrasonic temperature and ultrasonic time on the removal of Hg²⁺from aqueous solution by mesoporous silica alumina materials were investigated.The suitable synthesis conditions were determined as follows:NaOH alkali melting temperature 350℃,NaOH alkali melting time 350℃/Fly ash is 1/1.2,alkali melting time is 60 min,ultrasonic strength is 35 kHz,ultrasonic temperature is50℃and ultrasonic time is 60 min.The mesoporous silica alumina adsorbent material is a typical mesoporous material with the pore size of 2-25 nm,accounting for 89.627%of the total pore volume.The mechanism of ultrasonic assisted process was proved by SEM and bet analysis.Ultrasonic not only separated the adsorbent material with better adsorption effect from the solid silica product,but also improved the porosity of the adsorbent material.Through FTIR analysis,it can be seen that the ultrasonic exposure of the unburned carbon in the silica products,which also improves the adsorption performance of the adsorption materials.The adsorption process of mesoporous Si-Al adsorption material is not affected by the surface electricity,but depends on the properties of the mesoporous Si-Al adsorption material itself;the adsorption amount is directly proportional to the amount of adsorbent added;the adsorption process will have a saturated adsorption time with the increase of adsorption time,and the adsorption amount will not change greatly with the increase of adsorption time;the number of cycles experiment shows that the cycle of mesoporous Si-Al adsorption material.The adsorption performance is good,and the decrease of adsorption performance is not significant after 5 cycles.Through the analysis of adsorption equation,the correlation of Langmuir adsorption isotherm equation,Freundlich adsorption isotherm equation and Temkin adsorption isotherm equation are 0.9975,0.9514 and 0.991,respectively.The order of fitting effect is Langmuir>Temkin>Freundlich,and the adsorption of Hg²⁺by mesoporous Si-Al adsorption material conforms to Langmuir equation.The adsorption process is single molecular layer chemical adsorption,the maximum adsorption capacity of Hg²⁺is 7.937 mg/g,and the adsorption capacity of raw fly ash for mercury ion is 0.18 mg/g.The adsorption of Hg²⁺by mesoporous silica alumina adsorbent is not only controlled by the internal diffusion process,but also by the adsorption site activity.The hydroxy sodalite in the mesoporous Si-Al adsorption material has strong ion exchange performance,so the adsorption process is the exchange of sodium and mercury ions in hydroxy Sodalite,and the exchange of silicon aluminum active sites and mercury ions.There are 35 figures,7 tables and 88 references.更多还原