【作者】 樊明德；

【导师】 陈天虎；

【作者基本信息】 合肥工业大学 ， 环境工程， 2006， 硕士

【摘要】 层状双氢氧化物（layered double hydroxide,LDH）具有特殊的结构和性质,是国际材料学科与化学学科近10余年来研究的持续热点。在环保中的应用是其应用研究的重要领域,显示出广阔的前景。 本论文分别以含Zn²⁺、Cu²⁺废水为处理对象,研究在废水处理过程中利用Zn²⁺、Cu²⁺即时合成LDH消除污染,实现废物资源化的可行性,并考察优化了体系终点pH值、配料中Mg/Zn或Mg/Cu摩尔比值、反应温度、反应时间及废水中Zn²⁺或Cu²⁺初始浓度、阴离子种类等影响因素,多方面探讨了Zn²⁺、Cu²⁺去除机理,与化学沉淀法进行了比较。借助X-射线衍射分析、比表面积分析、透射电镜分析进行了热处理LDH结构演化和矿物纳米孔材料制备研究。 结果表明,实验条件下废水中Zn²⁺的去除只受pH值影响,9.0～11.0范围内除锌效果最佳,达99%以上,与化学沉淀法相比即时合成法处理效果更好,适用pH值范围更广,用来处理含Zn²⁺废水更具优势。废水中Cu²⁺的去除受pH值和配料中Mg/Cu摩尔比值影响显著,9.0～11.0pH范围内除铜效果最佳,达99%以上,随着Mg/Cu摩尔比值的加大,Cu²⁺去除率逐渐降低,但仍可取得理想效果。即时合成LDH处理含Zn²⁺、Cu²⁺废水具有可行性,产物三元LDH主要在晶体生成阶段形成,是一种功能材料,实现了废物资源化利用。 对层间阴离子主要为CO₃^2-的Mg/Al-LDH进行热处理,结果表明:在300℃左右脱除层间水,层结构发生收缩;400℃～550℃之间形成方镁石结构氧化物;温度高于600℃方镁石结构氧化物进一步相变为尖晶石结构氧化物。在层状双氢氧化物脱出结构水形成氧化物的过程中,由于结构水的脱出形成纳米孔隙,但仍保留原来LDH片状晶体假象形貌,并继承原来的晶体结构取向。煅烧形成的具有方镁石结构氧化物可以重新水化形成LDH,但重新水化形成的LDH结晶度比原来的LDH结晶度低。更多还原

【Abstract】 Layered double hydroxide(LDH) has been becoming international focus in material and chemistry fields in recent 10 years for its special structure and properties. Application of LDH in environmental protection is an important and promising attempt.The possibility of Zn2+ or Cu2+ removal from synthetic wastewater by preparing LDH in situ was investigated experimently. In this process LDH was prepared by Mg2+, Al3+ and Zn2+ or Cu2+ coprecipitating with NaOH. The effects of pH, Mg/Zn molar ratio or Mg/Cu molar ratio, reaction time, reaction temperature, Zn2+ or Cu2+ initial concentration and anions existed in synthetic wastewater were studied when M2+/M3+ molar ratio is 2. The removal efficiency of Zn2+ is found to be different significantly under the 0.05 level at different pH values, the most efficiency occurs in the pH range of 9.0 to 11.0, removes more than 99% of Zn2+ from synthetic wastewater, other factors have no significant effects on Zn2+ removal efficiency. The removal efficiency of Cu2+ is different significantly under the 0.05 level at different pH values and Mg/Cu molar ratio. The most efficiency occurs in the pH range of 9.0 to 11.0, removes more than 99% of Cu2+ from wastewater, Cu2+ removal efficiency is decreasing with the increasing of Mg/Cu molar ratio, however, relatively high removal efficiency can also be remained. The products were characterized by X-ray diffraction, indicates that Zn2+ or Cu2+ are removed from wastewater mainly occurs in the crystal formation stage as Zn/Mg/Al-LDH or Cu/Mg/Al-LDH, with consideration of the characteristics of the in-situ method itself. The products can be used as functional material, that means contaminations can be recycled. Compared with sedimentation treatment with NaOH, in-situ method for removal of Zn2+ is more effective and suit for more wider pH range.Structure evolution and BET surface area changes of heating treated Mg/Al-LDH was evaluated by X-ray diffraction, transmission electronmicroscopy and N2 Brunauer-Emmett-Teller analyses. The results indicates that for Mg/Al-LDH with carbonate as interlayer anion, periclase-like oxide is formed at the temperature range of 400℃-800℃. At the same time, 2nm-3nm nanometer mesopores are formed during the decomposition of LDH. However, the heat treated samples still preserves the morphology of original LDH plates. Periclase-like oxide formed from LDH heating treatment may re-hydrolyze and recover the structure of LDH. However, crystallinity of the recovered LDH is lower than that of original LDH. Such a heating treatment will result in the formation of Mg-Al-oxide nano-crystals and nanopores among the nano-crystal. When the heating temperature exceeds 1000℃, the periclase-like Mg-Al-oxide is transformed into a composite with periclase (MgO) and spinel phases.the periclase can be re-hydrolyzed and dissolved in HCl solution. After acid treatment ,the sample with high surface area is composed of spinel nano-crystals and nanopores among them.更多还原