【作者】 周波；

【导师】 周建飞；

【作者基本信息】 四川大学 ， 皮革化学与工程， 2021， 硕士

【摘要】 制革工业是我国的特色优势产业,在国民经济中占据着不可或缺的地位。然而,制革过程产生的大量制革污泥给我国皮革行业的健康持续发展带来了严峻挑战。制革污泥是制革废水处理的终端产物,富含有机质,极易腐化发臭,同时可能还含有大量病原体、寄生虫和重金属铬等有毒有害物质,如果处理不当,会对生态环境造成危害。因此,对制革污泥的资源化利用意义重大。热解是目前较有发展潜力的制革污泥处理方式之一,制革污泥高温炭化不仅能杀灭病原体、降解有机物、固定重金属,而且其产物制革污泥生物炭(tannery sludge biochar,TSBC)还可作为吸附剂、催化剂和土壤改良剂用于环境修复等领域,从而实现“以废治废”。本论文采用“以废治废”的研究思路,将制革污泥作为研究对象,探究了不同热解温度对所制备的制革污泥生物炭(TSBC)理化性质的影响规律,并在此基础上考察了其在催化降解或吸附去除废水中污染物的应用潜力,拟为制革行业的绿色发展提供技术支撑。在第一部分研究工作中,采用传统热解法制备制革污泥生物炭(TSBC),并系统研究了不同热解温度下(300、400、500、600、700、800℃)所制备TSBC的理化性质差异。结果表明:制革污泥是一种富含有机质和无机金属离子的工业污泥,具有制备生物炭的潜力。随着热解温度的升高,TSBC的表面粗糙度、孔容、比表面积和芳香性呈现先增大后减小的趋势,并均在500℃时达到最大值。在500℃下制备得到TSBC500的比表面积和孔径分别为40.98 m2/g和0.097 cm3/g。TSBC上存在大量方解石(CaCO3)、含镁方解石(Mg0.03Ca0.97(CO3))和石英(SiO2),导致TSBC自身呈碱性。TSBC的碳结构主要成分为石墨炭与非定型炭,且由于制革污泥中的多种金属以及氮和硫元素的存在,使其缺陷碳的含量远高于一般生物炭。TSBC表面还存在多种含氧基团,且当热解温度为500℃时,TSBC表面含有的羧基最为丰富。在第二部分研究工作中,系统研究了 TSBC作为催化剂活化过硫酸盐(PS)降解四环素(TC)的可行性,考察了 TSBC用量、pH、PS浓度和共存离子等条件对TC降解的影响,并探讨了 TSBC对PS的活化机制和TC的降解反应历程。结果表明,在500℃热解所制备的TSBC500对PS有最佳活化效果。此外,在pH为3-9范围内,当TSBC500投加量为0.3 g/L、PS浓度为3 mM时,TSBC500/PS体系对溶液中TC的去除率均大于98.1%。进一步通过自由基猝灭和捕获实验测定了 TSBC500/PS降解TC过程中的活性氧物质,发现·OH和SO4·-起主要作用。并且TSBC500上的过渡金属(如Fe、Cr等)、含氧官能团(如羧基、羟基等)以及高度的碳结构缺陷均有利于TSBC500活化PS降解TC。溶液中的共存离子HCO3-、SO42-、NO3-和 Cl-对TC降解影响微弱,而H2PO4-会稍微降低TC去除率,主要是因为其能猝灭部分SO4·-和·OH,且能与TSBC500上的Fe发生螯合作用。此外,实际自来水体系下TC的降解率会稍有下降,但仍有90.1%。循环催化降解实验表明,TSBC500具有良好的稳定性和重复使用性,循环4次后仍有79.8%的TC去除率,且热处理后催化能力又重新恢复,具有巨大的催化潜力。在第三部分研究工作中,研究了 TSBC对单系统TC和亚甲基蓝(MB)的吸附性能,通过静态吸附实验,考察pH值、反应温度、接触时间、污染物浓度和共存离子等不同参数对TSBC去除TC和MB的影响,并对TSBC吸附去除TC和MB的相关机理进行研究。结果表明,热解温度500℃下所制备的TSBC500同时拥有对TC与MB最佳的吸附效果。TSBC500对TC与MB的吸附速率很快,吸附过程均符合拟二级动力学模型。TC的吸附等温线符合Freundlich方程,而MB的吸附等温线符合Langmuir方程。在25℃下,TSBC500对TC与MB的最大吸附容量分别达到116.9 mg/g和75.4 mg/g。通过表征对吸附机理的研究发现,TSBC500对TC的吸附作用主要是依靠金属螯合、氢键、π-π电子供体-受体(π-πEDA)和孔填充作用等,而对MB的吸附作用主要是依靠静电吸引、π-πEDA、孔填充和离子交换作用等。继续研究了共存离子对TSBC500吸附去除TC与MB的影响,结果发现共存离子Cl-、SO42-、CO32-、NO3-、Na+和K+对TSBC500吸附TC与MB几乎无影响,但Mg2+和Ca2+的存在会略微抑制TC与MB的吸附。吸附饱和后的TSBC500可以通过乙醇解析快速再生,6次吸附循环后对TC与MB的去除率仍有61.7%与74.5%,展现出TSBC500良好的循环吸附使用性能。更多还原

【Abstract】 Leather industry is a dominant industry in China,which plays an indispensable role in the national economy.However,a large amount of tannery sludge produced from leather processing has posed serious challenges to the sustainable development of the leather industry.Tannery sludge,which contains a large number of organics,pathogens,parasites,chromium and other toxic and harmful substances,is the end product of tannery wastewater treatment.The improper disposal of tannery sludge will cause great threat to ecological environment.Therefore,it is of great significance to the resource utilization of tanning sludge.At present,pyrolysis is a promising treatment method for tanning sludge,which could not only exterminate pathogens,degrade organic matter,and fix heavy metals,but also gain the tannery sludge biochar(TSBC)as adsorbent,catalyst,or soil conditioner for environmental remediation.Tannery sludge was used as the subject in this study,and the effects of pyrolysis temperature on the physicochemical property of TSBC were investigated.On this basis,the potential application of TSBC as an adsorbent or catalyst for pollutants removal from wastewater was investigated,and a research idea of "treating waste with waste"was formed,which provided technical support for the green development of leather industry.In the first part of this thesis,tannery sludge was used as raw material to prepare TSBC by traditional pyrolysis method,and the effects of pyrolysis temperature(300,400,500,600,700,800℃)on the physicochemical property of TSBC were investigated.The results indicated that the tannery sludge is a kind of industrial sludge rich in organic matter and inorganic metal ions,which shows the potential to prepare biochar.The surface roughness,pore volume,specific surface area and aromaticity of TSBC first increased and then decreased with the pyrolysis temperature increasing,and the properties reached the maximum at 500℃.The specific surface area and pore volume of TSBC500 prepared at 500℃ were 40.98 m2/g and 0.097 cm3/g,respectively.TSBC consisted of calcite(CaCO3),magnesium bearing calcite(Mg0.03Ca0.97(CO3))and quartz(SiO2),which caused that TSBC was alkaline.The carbon structure of TSBC was mainly composed of graphite carbon and amorphous carbon,and the content of defective carbon was much higher than that of general biochar due to the existence of various metals,nitrogen and sulfur elements in tannery sludge.Besides,TSBC500 own the most abundant oxygen-containing groups.In the second part of this thesis,the feasibility TSBC as a catalyst for Persulfate(PS)activation to degrade tetracycline(TC)was studied,and the effects of TSBC dosage,pH,PS concentration,and coexisting ions on the TC removal efficiency were investigated.Besides,the activation mechanism of PS by TSBC and its degradation mechanism of TC in the TSBC/PS system were further investigated.It was found that TSBC500 showed the superior activation for PS,the removal efficiencies of TC reached up to 98.1%in TSBC500/PS system after treating with 0.3 g/L of TSBC500 and 3 mM of PS in the pH range of 3-9.Besides,free radical quenching and trapping experiment indicated that·OH and SO4·" played the major role for TC removal in TSBC500/PS system,and the transition metal(eg.Fe,Cr),oxygen-containing functional groups(eg.carboxyl,hydroxyl),and the high degree of carbon structural defects were beneficial for PS activation to degrade TC.The coexisting ions(eg.HCO3-,SO42-NO3-and Cl-)played little effect on the TC removal efficiency,while H2PO4-slightly decreased the TC removal efficiency.This phenomenon was mainly due to the fact that H2PO4-could quench the SO4·-and·OH.In addition,under the actual tap water system,the degradation rate of TC will decrease slightly,but it was still 90.1%.The results of cycle experiments showed that TSBC500 had good stability and reusability.The removal rate of TC was still 79.8%in the fourth cycle,and the catalytic ability could be restored after heat treatment,which proved it had great catalytic potential.In the third part,the adsorption performance of TSBC towards TC and MB in the single system was studied,and the effects of pH,reaction temperature,contacting time,pollutants concentration,and coexisting ions on the TC and MB removal efficiency were investigated.Besides,the adsorption mechanism was further discussed.The results indicated that TSBC500 showed the superior removal efficiency of TC and MB.TC and MB were adsorbed rapidly,and the maximum adsorption capacity was relatively high(116.9 mg/g for TC and 75.4 mg/g for MB).Besides,the adsorption process of TC was in accordance with a pseudo-second-order kinetics and the Freundlich isotherm well,while the adsorption process of MB was in accordance with a pseudo-second-order kinetics and the Langmuir isotherm well.The adsorption mechanism of TSBC500 on TC was mainly dependent on the metal chelation,hydrogen bonding,π-π electron donor-acceptor(π-πEDA)and pore filling,while the adsorption mechanism of TSBC500 on MB was mainly dependent on the electrostatic attraction,π-πEDA,pore filling and ion exchange.Except that Mg2+and Ca2+had a slight inhibition effect on the adsorption of TC and MB,the other investigated co-existing ions(eg.Cl-、SO42-、CO32-、NO3-、Na+and K+)played little effect on TC and MB removal.The removal efficiency of TC and MB reached up to 61.7%and 74.5%in the sixth cycle,respectively.This study illustrated that TSBC500 has great potential applications as an environmentally friendly desirable adsorbent for the efficient removal of organic pollutants from wastewater.更多还原