Design And Preparation Of Novel Nickel-Based Materials And Their Adsorption Properties For Arsenic

Arsenic is one of the most dangerous and toxic pollutants in groundwater and poses a serious threat to the health of millions of people around the world.Higher levels of arsenic have been detected in drinking water in 13 provinces of China.Prolonged exposure to arsenic-containing wastewater can cause cancer,skin disease,and severe damage to blood vessels,liver,kidney,and central nervous system.Therefore,there is an urgent need to remove arsenic by appropriate methods.Adsorption is considered as one of the most effective methods for removing arsenic from aqueous solutions because of its low cost,simple operation,and environmental friendliness.Therefore,in this thesis,we prepared novel nickel-based composite materials for removal of arsenic????As????from wastewater.The removal performance of As???from aqueous solution by nickel-based composite materials were investigated by batch experiments,and their adsorption mechanism for As???were also discussed by advanced analytical methods.The main research contents are as follows:1.NiAl layered double hydroxide?NiAl-LDH?was synthesized by one-step hydrothermal method,then NiAl-LDH was calcined at a certain temperature to synthesize layered double oxide?NiAl-LDO?,which was used as adsorbent to remove As???from the aqueous solution.The effects of different factors,including solution pH,reaction time,temperature,initial As???concentration and solid-liquid ratio,were systematically studied by batch experiments.The adsorption isotherm experiments results showed that the adsorption process of As???on materials to be calcined at different temperatures conformed to the Langmuir model.It was found that the adsorption capacity of these composites for As???can be adjusted by controlling the calcination temperature,and their adsorption capacity are as follows:NiAl-LDO₅₀₀?198.1 mg/g?>NiAl-LDO₄₀₀?180.9 mg/g?>NiAl-LDO₃₀₀?160.2 mg/g?>NiAl-LDO₆₀₀?121.4 mg/g?>NiAl-LDH?60.7 mg/g?.Among them,NiAl-LDO500 exhibited the maximum adsorption capacities for As???.Then the effect of pH on the adsorption of As???on NiAl-LDO₅₀₀ was studied.It was found that the NiAl-LDO₅₀₀ exhibited high adsorption capacity at low pH and a lower adsorption capacity at high pH.The results of adsorption kinetic experiments showed that the efficient and rapid adsorption process of As???by NiAl-LDO₅₀₀ conformed to the pseudo-second order kinetics model,and adsorption was an efficient and rapid process.Thermodynamic experiments indicated that the adsorption of As???by NiAl-LDO₅₀₀ was a endothermic and spontaneous process.2.Magnetic chestnut-shell hollow carbon sphere structure NiO_x/Ni@C composites were prepared with Ni-MOF as the self-sacrificing precursor and used as adsorbents for removal of As???.Compared with the precursor Ni-MOF,the synthesized NiO_x/Ni@C has the advantages of high specific surface area and good dispersion,indicating that NiOx/ni@c can be used as an ideal adsorption material.Therefore,the effects of solution pH,initial As???concentrated,temperature and reaction time on the adsorption of As???on NiOx/Ni@C were systematically studied by batch experiments.The adsorption isotherm experiments results showed that the adsorption process of As???on various calcination temperatures conformed to the Langmuir model,and their adsorption capacity was calculated by Langmuir model.It exhibited a maximum removal capacity of 454.94 mg/g at pH=3.0 and 298 K that owing to NiO/Ni@C400 is rich in oxygen-containing functional groups and has large specific surface area.NiO/Ni@C400 adsorbents also exhibited a very wide range of pH suitability due to its good thermal and chemical stability.The adsorption process of As???was found to be less susceptible to coexisting ions,providing support for NiO/Ni@C400 to remove As???in the real environment..In addition,adsorption kinetic experiments showed that removal of As???by NiO/Ni@C400 was a fast and efficient process.Because of the simple synthesis method,ultra-high adsorption capacity and simple magnetic separation method,NiO/Ni@C400 has a broad application prospect in the treatment and disposal of wastewater containing As???.