【作者】 杨波；

【导师】 苏仕军； 陈博宇；

【作者基本信息】 四川大学 ， 环境工程（专业学位）， 2021， 硕士

【摘要】 重金属铅离子在环境中不易降解,性质稳定,对水环境和人体健康危害极大。吸附法是目前去除水中重金属离子比较高效和具有较好前景的方法之一,而锰氧化物已被证实是去除废水中重金属离子的有效吸附剂之一。但是,目前大多数锰氧化物吸附剂都是以高锰酸钾和硫酸锰等商品锰盐为原料制备而成,存在成本高、工艺繁琐等问题。同时半氧化锰矿锰的价态复杂,Mn²⁺、Mn³⁺和Mn⁴⁺共存,直接浸出难以获得满意的锰回收效率。本文以半氧化锰矿作为原料,首先通过硫酸浸出其中的酸溶性锰和其他杂质,获得含有硫酸锰的浸出液,得到比表面积大、具有多孔结构、富含二氧化锰活性组分的浸出渣,然后将浸出渣经水洗作为吸附剂,用来去除模拟废水中的铅离子,同时研究了该吸附剂的吸附特性和吸附机理。浸出条件对半氧化锰矿中锰浸出率和锰氧化物吸附剂吸附性能的影响。利用稀硫酸溶液浸出半氧化锰矿,并将浸出渣洗涤后得到锰氧化物吸附剂（MO）。研究了液固比、浸出时间、硫酸浓度和浸出温度对锰浸出率和铅离子吸附量的影响。实验结果表明,当实验条件为:液固比为5:1、硫酸浓度为3mol/L、浸出时间为120 min和浸出温度为90℃时,锰浸出率为62.89%,MO对铅离子的平衡吸附量为95.3mg/g,较原矿提高了4.6倍。研究了半氧化锰矿浸出动力学的控制过程,结果表明该浸出过程为混合控制。利用XRF、SEM、XRD、FTIR、BET等表征手段对半氧化锰矿和MO进行了表征分析。结果表明,MO中的锰含量由半氧化锰矿的29.39%提高至37.51%,半氧化锰矿中大部分的碳、钙、镁等杂质都得以去除,MO表面由原本的无规则堆积趋近于球状结构,出现大量的孔隙结构,比表面积由原矿的8.531m²/g提高至68.469m²/g,总孔容积由0.057cm³/g提高至0.251cm³/g,平均粒径由原矿的26.510nm下降至14.632nm。半氧化锰矿和吸附剂的N₂吸附-脱附曲线表明,原矿和吸附剂的吸附等温线为属于BDDT中的第IV类曲线,其滞后环属于H₃类型,这表明了原矿和吸附剂都是介孔材料。吸附剂对模拟废水中铅离子的吸附特性。我们研究了p H值、吸附温度、吸附剂投加量以及铅离子初始浓度对铅离子吸附性能的影响。结果表明,增大p H值、提高初始铅离子浓度和吸附温度均能提高吸附剂的吸附性能,但是当吸附剂投加量增加时并不利于铅离子的吸附。在溶液p H值为5.0、30℃的吸附温度的条件下,MO的最佳投加量为1.25g/L,于120min吸附达到平衡。随后我们研究了吸附过程中的吸附等温线、动力学、热力学等。吸附等温线结果显示,MO对铅离子的吸附行为与Langmuir模型匹配度很高,且MO吸附铅离子的行为属于单分子层吸附。热力学研究结果显示,在MO吸附铅离子过程中,?G值小于0,?H和?S小于0,这表明该吸附过程属于自发的吸热反应。动力学相关拟合数据表明,伪二级动力学能很好的描述MO对铅离子的吸附行为,这说明这一吸附过程属于化学吸附,表观活化能（Ea）和频率因子（A）分别为6.417k J/mol和0.0733。对铅、镉、铜、钴、镍等几种重金属离子进行了单独吸附和混合吸附,研究其吸附性能,结果表明MO对这几种金属离子均有一定的吸附效果,且吸附性能大小顺序为铅>铜>镉>钴>镍。最后,对吸附剂进行了解吸再生实验,结果表明MO具有良好的吸附再生性能,能够循环多次使用。吸附剂对废水中铅离子的吸附机理。我们使用EDS、XRD、XPS、FTIR等表征手段分析MO对铅离子的吸附机理。XRD结果表明,溶液中的铅离子已被吸附到吸附剂表面上,且生成了Pb_2-xMn₈O₁₆;FTIR、XPS结果表明吸附剂上的羟基官能团对吸附过程起主要吸附作用。探究了铅离子吸附量和氢离子释放量的关系,结果表明,吸附剂在吸附过程中每吸附1个摩尔量的Pb²⁺,就会释放1.503个摩尔量的H⁺,且铅吸附在MO表面的形式为Pb OH⁺和Pb²⁺。本文通过硫酸溶液浸出半氧化锰矿的方式获得硫酸锰溶液和富含二氧化锰的重金属吸附材料,实现了半氧化锰矿中不同存在形态的锰的综合高效利用,为半氧化锰矿的资源利用和锰氧化物吸附剂的制备提供了一种新的工艺路线。更多还原

【Abstract】 The heavy metal lead ion is not easy to degrade in the environment and is stable in nature,which is very harmful to water environment and human health.Adsorption is one of the most efficient and promising methods for the removal of heavy metal ions from wastewater,and manganese oxide has been proved to be one of the effective adsorbents for the removal of heavy metal ions from wastewater.However,at present,most manganese oxide adsorbents are prepared from commercial manganese salts such as potassium permanganate and manganese sulfate,which have problems such as high cost and complicated process.At the same time,the valence state of manganese in semi-manganese oxide ore is complex,and Mn²⁺,Mn³⁺and Mn⁴⁺coexist,so it is difficult to obtain satisfactory recovery efficiency of manganese by direct leaching.With semi-oxidized manganese ore as raw materials,this paper first by sulfuric acid leaching of acid soluble manganese and other other impurities,eaching liquid containing manganese sulfate,large surface area,with porous structure,rich in manganese dioxide leaching residue of active components,then the leaching residue are washed as adsorbent,used to remove the lead ions in the simulated wastewater,and studied the adsorption properties of adsorbent and adsorption mechanism.Effect of leaching conditions on leaching rate of manganese in manganese oxide ore and adsorption performance of manganese oxide adsorbent.Manganese oxide adsorbent（MO）was obtained by leaching semi-oxidized manganese ore with dilute sulfuric acid solution and washing the leaching residue.The effects of liquid-solid ratio,leaching time,sulfuric acid concentration and leaching temperature on manganese leaching rate and lead ion adsorption capacity were studied.The experimental results show that when the experimental conditions are as follows:liquid-solid ratio of 5:1,sulfuric acid concentration of 3mol/L,leaching time of 120min and leaching temperature of 90℃,the leaching rate of manganese is 62.89%,and the equilibrium adsorption capacity of MO to lead ions is 95.3mg/g,which is 4.6times higher than that of raw ore.The control process of leaching kinetics of semi-oxidized manganese ore was studied.The results show that the leaching process is mixed control.XRF,SEM,XRD,FTIR,BET and other characterization methods were used to characterize the manganese oxide ore and MO.Results show that MO from manganese oxide in manganese content in the 29.39%to 37.51%,most of the carbon in a half manganese oxide,calcium,magnesium and other impurity removal,MO surface is made of original without rules tend to be spherical structure,a large number of pore structure,specific surface area from ores of 8.531m²/g to 68.469m²/g,total pore volume increased from 0.057cm³/g and 0.251cm³/g,the average particle size of raw ore decreases from 26.510nm to 14.632nm.N₂ adsorption-desorption curves of manganese oxide ore and adsorbents show that the adsorption isotherm of raw ore and adsorbents belongs to the class IV curve of BDDT,and its hysteresis loop belongs to the type of H₃,which indicates that both raw ore and adsorbents are mesoporous materials.Adsorption characteristics of lead ions in simulated wastewater by adsorbents.The effects of p H value,adsorption temperature,dosage of adsorbent and initial concentration of lead ions on the adsorption properties of lead ions were investigated.The results show that increasing the p H value,increasing the initial lead ion concentration and the adsorption temperature can improve the adsorption performance of the adsorbent,but the increase of the amount of adsorbent is not conducive to the adsorption of lead ions.Under the conditions of p H value of 5.0 and adsorption temperature of 30℃,the optimal dosage of MO is 1.25g/L,and the adsorption equilibrium is reached in 120min.Then we studied the adsorption isotherm,kinetics and thermodynamics in the adsorption process.The results of adsorption isotherm show that the adsorption behavior of MO for lead ions is highly matched with the Langmuir model,and the adsorption behavior of MO for lead ions belongs to monolayer adsorption.Thermodynamic study results show that the value of?G is less than 0 and the value of?H and?S are less than 0 in the process of MO adsorption of lead ions,indicating that the adsorption process belongs to spontaneous endothermic reaction.Kinetic correlation fitting data show that the pseudo-second-order kinetics can well describe the adsorption behavior of MO to lead ions,which indicates that the adsorption process belongs to chemical adsorption,and the apparent activation energy（Ea）and frequency factor（A）are 6.417k J/mol and 0.0733,respectively.Several heavy metal ions such as lead,cadmium,copper,cobalt and nickel were adsorbed separately and mixed to study their adsorption properties.The results showed that MO had certain adsorption effect on these metal ions,and the order of adsorption properties was Pb²⁺>Cu²⁺>Cd²⁺>Co²⁺>Ni²⁺,the adsorption and regeneration experiments of the adsorbent were carried out.The results showed that MO had good adsorption and regeneration performance and could be used for many times.Adsorption mechanism of lead ions in wastewater by adsorbent.We used EDS,XRD,XPS,FTIR and other characterization methods to analyze the adsorption mechanism of MO to lead ions.The XRD results show that the lead ions in the solution have been adsorbed on the surface of the adsorbent and Pb_2-xMn₈O₁₆has been formed.FTIR and XPS results showed that the hydroxyl functional groups on the adsorbent played a major role in the adsorption process.The relationship between lead ion adsorption and hydrogen ion release was investigated.The results show that1.503 moles of H⁺will be released for each mole of Pb²⁺adsorbed by the adsorbent during the adsorption process,and the forms of Pb adsorption on MO surface are Pb OH⁺and Pb²⁺.In this paper,manganese sulfate solution and heavy metal adsorption materials rich in manganese dioxide were obtained by leaching manganese oxide ore in sulfuric acid solution,which realized the comprehensive and efficient utilization of different forms of manganese in manganese oxide ore,and provided a new technological route for the resource utilization of manganese oxide ore and the preparation of manganese oxide adsorbent.更多还原