硫酸镁颗粒高效分离油包水乳液

Mangesium sulfate microparticles with superior performance in water separation from a water-in-oil emulsion

乳化油中微量水分的分离脱除是工业废油净化,实现资源化回用的关键步骤.本研究通过乙二胺四乙酸(EDTA)诱导Mg^(2+)和SO_(4)^(2−)结晶,成功合成单分散硫酸镁微米颗粒(MgSO_(4)·1.25H_(2)O,MSH).该颗粒在脱除乳化水分方面具有优异的性能,针对含10 mg/mL水的乳化变压器油:(1)添加16.0 g/L_(oil) MSH可去除95.56%的水分,提高添加量或分离温度可进一步提高水分去除率至98.74%;(2)颗粒吸水后尺寸从4.1μm膨胀至40μm,易于从油中分离,无残留;(3)可循环再利用,初步估算处理每立方乳化油成本为733.68元,低于目前报道的其他材料.机理探讨发现,MSH优异的除水功能归功于其在常温下可重排的晶格结构,可腾出空间来捕获并固定乳化油中的微量水分(水分固定于MSH晶格间隙),其晶格空间水容量达0.63 g_(H_(2)O)/g_(MSH),分别是已报道的双金属氧化物(LDO,0.48 g_(H_(2)O)/g_(LDO))和半水硫酸钙(HH,0.18 g_(H_(2)O)/g_(HH))的1.31和3.50倍.本研究结果将为工业乳化废油的提纯净化提供新的策略和材料,积极推进我国工业废油的绿色高效资源化回用进程,符合国家节能环保战略需求.

Nowadays the rapid development in the transportation,mining,chemical and machinery industry has dramatically raised the consumption of both petroleum and synthetic oil products(such as lubricating oil,transformer oil,etc.),which,as a result,leads to the production of million tons of waste oil every year(the waste oil is referred to the one that has totally or partially lost the function due to the inclusion of impurities and the change in its composition).These waste oils have posed a huge threat to the ecological safety of the environment(e.g.,oil-induced water,air and soil pollution).It is therefore urgent to find efficient approaches for proper and safe disposal of them.Oil regeneration through a stepwise purification(removal of water,acids,particles,etc.)-refining(rectification,hydrogenation,hydrodechlorination,etc.)strategy is one promising and green alternative,which also contributes to saving the petroleum resources.Separation/removal of trace water from emulsified oil is an indispensible but challenging step in the purification of waste oil before its refining.Current techniques,including the magnetic separation,oil skimming,selective adsorption and membrane filtration,have afforded unsatisfactory performances towards the emulsified waste oil,primarily due to the high oil viscosity,low water content,small droplet size and high stability of the emulsion.Herein,we report a facile and green approach to the monodisperse magnesium sulfate microparticles(MgSO_(4)∙1.25H_(2)O,MSH)via an ethylene diamine tetraacetic acid(EDTA)-induced self-assembly strategy,and demonstrate their superior performances in removal of trace water from the emulsified transformer oil.Specifically,16.0 g/Loil of MSH enables to treat 20 mL of emulsion(water content:10 mg/mL)with a separation efficiency of 95.56%,and intriguingly this efficiency can be increased to 98.74%when increasing the MSH dose or the separation temperature.Furthermore,after use,the MSH is converted to larger microparticles with its mean size increasing from 4.1 to 40µm,and can therefore be readily collected from the oil phase,avoiding the oil contamination by the solid phase.The collected solid phase can be regenerated to MSH particles that preserve the robust oil/water separation performance,and this unique renewable feature improves the economics of oil purification.Accordingly,purification of every cubic meter of emulsion(water content:10 mg/mL)costs about 733.68 yuan,much lower than other materials reported in the literature.The mechanism study reveals that the water removal function of MSH is attributed to its rearrangeable lattice structure at room temperature,which releases extra space to capture and fix the water in its lattice gap.The water capacity of MSH reaches 0.63 g_(H_(2)O)/g_(MSH),which is 1.31 and 3.50 times the reported bimetal oxide(LDO,0.48 g_(H_(2))O/g_(LDO))and calcium sulfate hemihydrate(HH,0.18 g_(H_(2)O)/g_(HH)),respectively.This research provides new strategies and materials specific for the purification of industrial emulsified waste oil,and actively promotes its recycling in a green and efficient way.