【作者】 李涛；

【导师】 官月平；

【作者基本信息】 北京科技大学 ， 材料科学与工程， 2021， 博士

【摘要】 重金属铬(Cr)是一种对人体健康危害极大的致癌物质,水系中超标的铬也会对水生生物造成极大的危害。我国是一个铬矿产资源贫乏的国家,制革企业每年产生大量的含铬废水和含铬固体危险废弃物,造成严重的铬资源浪费和由铬引起的环境污染。河北省开始执行《制革及毛皮加工工业水污染物排放标准GB 30486-2013》,该标准将总铬排放标准从1.5 mg/L减小到0.5 mg/L。目前,制革企业处理含Cr(Ⅲ)废水的方法难以使处理后废水出口总铬浓度小于0.5 mg/L,同时还会产生大量的含铬危险废弃物,铬资源也不能回收。本论文提出了一种用磁性Fe3O4纳米颗粒处理制革含Cr(Ⅲ)废水的新机理,设计制造了一种新型钕铁硼(Nd-Fe-B)高强磁棒式磁分离器,系统地研究了磁性Fe3O4纳米颗粒处理制革含Cr(Ⅲ)废水工艺,开展了实验室规模和中试规模制革含Cr(Ⅲ)废水处理实验,建成了制革含Cr(Ⅲ)废水处理示范工程。提出了一种新的去除制革含铬废水中Cr(Ⅲ)的“Fe3O4-Cr(OH)3”团簇机理。这种机理跟传统的吸附机理有着本质的区别,其对Cr(Ⅲ)具有高选择性和超高的捕获容量。磁性Fe3O4纳米颗粒和“水合Cr(OH)3胶体团簇”结合形成“纳米团簇”的数目和尺寸不受磁性纳米颗粒比表面积的限制,因而理论上来说磁性纳米颗粒对“水合Cr(OH)3胶体团簇”的捕获容量是无限的,其对Cr(Ⅲ)的分离效率是巨大的,所以才能够实现对废水中Cr(Ⅲ)如此大的捕获容量。在pH 8时,表面裸露磁性Fe3O4纳米颗粒对Cr(Ⅲ)的最大捕获容量为452.6mg/L。设计制造了一种新型的钕铁硼(Nd-Fe-B)高强磁棒式磁性分离器。磁性分离器主体是由呈正三角形垂直排列的磁棒组成。该磁性分离器具有体积小、处理量大、能耗低等优点,能在不移动磁棒的情况下实现磁棒表面的清洁。采用加入磁性Fe3O4纳米颗粒的水作为模拟液,研究了磁性分离器捕获磁性Fe3O4纳米颗粒的效率。当磁性Fe3O4纳米颗粒浓度小于400mg/L、流速小于18 L/h、磁棒间距小于30 mm时,在3小时内,磁性分离器对磁性Fe3O4纳米颗粒的捕获率大于99.4%。在此基础上,设计制造了处理量分别为2-5 m3/h和10-15 m3/h的中试和示范工程规模的磁性分离器。进行连续流动处理制革含Cr(Ⅲ)废水实验室规模实验,磁棒间距30mm,入口流速18 L/h,两级处理后废水总铬浓度降低至0.2 mg/L左右,满足排放标准。用10%的次氯酸钠(NaClO)溶液对使用后的磁性Fe3O4纳米颗粒进行再生,可实现对磁性Fe3O4纳米颗粒接近100%再生和对废水中的铬99%以上回收,无危险废弃物产生。再生磁性Fe3O4纳米颗粒循环用于制革含Cr(Ⅲ)废水处理,处理后废水总铬浓度稳定小于0.5 mg/L。中试实验以2 m3/h的流速运行,每天工作8小时,每4小时启动原位清洁装置清洗磁棒,连续运行15天。处理后废水总铬浓度稳定小于0.5 mg/L。示范工程以10 m3/h的流速运行,连续7天间歇和连续稳定运行,全程处理后废水总铬浓度低于0.5 mg/L。建成了与示范工程配套的生产量为300 kg/天的磁性Fe304纳米颗粒生产线和处理量为300kg/天的“磁-铬”解离生产线。此外,传统废水处理技术难以使油田采出水COD小于50mg/L,或者成本很高。本论文提出了用磁性Fe3O4-IDA-Cu2+纳米颗粒去除经传统废水处理工艺处理后的油田采出水COD新机理。将磁性分离器用于去除COD的连续流动实验,COD去除率可达66.7%,处理后油田采出水COD稳定小于50 mg/L。使用后的磁性Fe3O4-IDA-Cu2+纳米颗粒能再生循环回用,再生循环回用6次,出口 COD浓度稳定小于50 mg/L。更多还原

【Abstract】 The heavy metal chromium(Cr)is a carcinogen that is extremely harmful to human health.Excessive chromium in aquatic ecosystem can also cause great harm to aquatic organisms.China is a country with poor chromium mineral resources.Leather tanning factories produce a large amount of chromium containing wastewater and solid hazardous waste every year,causing serious waste of chromium resources and environmental pollution.China’s Hebei Province began to implement the "Discharge standard of water pollutants for leather and fur making industry GB 30486-2013",which reduces the total chromium discharge standard from 1.5 mg/L to 0.5 mg/L.At present,it is difficult for leather tanning factories to treat Cr(Ⅲ)containing wastewater to make the outlet total chromium concentration of the treated wastewater less than 0.5 mg/L.At the same time,a large amount of chromium containing hazardous waste is generated,and chromium resources cannot be recycled.This paper proposed a new mechanism for the treatment of Cr(Ⅲ)containing tannery wastewater with bare magnetic Fe3O4 nanoparticles.Designed and manufactured an innovative neodymium iron boron(Nd-Fe-B)high strength magnetic bar separator.The process of treating Cr(Ⅲ)containing tannery wastewater with magnetic Fe3O4 nanoparticles was systematically studied.The laboratory and pilot scale Cr(Ⅲ)containing tannery wastewater treatment experiments were carried out.The demonstration project for the treatment of Cr(Ⅲ)containing tannery wastewater was completed.An innovative "Fe3O4-Cr(OH)3" cluster mechanism for removing Cr Ⅲ)in chromium containing tannery wastewater was proposed.This mechanism is essentially different from the traditional adsorption mechanism,and it has an ultra high selective capture capacity for Cr(Ⅲ).Magnetic Fe3O4 nanoparticles and"hydrated Cr(OH)3 colloidal clusters" are bound together to form "nanoclusters".The number and size of "nanoclusters" are not limited by the specific surface area of magnetic nanoparticles.Therefore,theoretically,the capture capacity of magnetic Fe3O4 nanoparticles for "hydrated Cr(OH)3 colloidal clusters" is infinite,and its separation efficiency for Cr(Ⅲ)is huge,so it can achieve such a high capture capacity for Cr(Ⅲ)in wastewater.At pH 8,the maximum capture capacity of the bare magnetic Fe3O4 nanoparticles for Cr(Ⅲ)is 452.6 mg/L.Designed and manufactured an innovative neodymium iron boron(Nd-Fe-B)high-strength magnetic bar type magnetic separator.The magnetic separator was composed of 4 vertically aligned magnetic bars in equilateral triangle.The magnetic separator with the advantages of small size,large processing capacity,low energy consumption,and the ability to clean the magnetic bar in situ.The magnetic Fe3O4 nanoparticles were added to water as a simulation solution,and the capture efficiency of the magnetic separator for magnetic Fe3O4 nanoparticles was studied.When the concentration of magnetic Fe3O4 nanoparticles is less than 400 mg/L,the flow rate is less than 18 L/h,and the distance between the magnetic bars is less than 30 mm,the capture efficiency of magnetic Fe3O4 nanoparticles by the magnetic separator is greater than 99.4%within 3 hours.Based on this,the pilot and demonstration project scale magnetic separator with processing capacity of 2-5 m3/h and 10-15 m3/h was designed and manufactured.The laboratory scale continuous flow treatment experiment of Cr(Ⅲ)containing tannery wastewater was carried out under optimal conditions,the magnetic bar distance was 30 mm,and the inlet flow rate was 18 L/h.The outlet total chromium concentration was reduced to about 0.2 mg/L after the secondary treatment,which meets the latest discharge standards.Sodium hypochlorite(NaCIO)solution(10%)was used to regenerate the spent magnetic Fe3O4 nanoparticles,which can achieve close to 100%regeneration of magnetic Fe3O4 nanoparticles,and realized the recovery of more than 99%of Cr(Ⅲ)in wastewater,and no hazardous waste was generated.The regeneration magnetic Fe3O4 nanoparticles were recycled for the treatment of Cr(Ⅲ)containing tannery wastewater,and the outlet total chromium concentration was stable to less than 0.5 mg/L.The pilot experiment was run at flow rate of 2 m3/h for 15 days,working for 8 hours per day,and the in-situ cleaning device was started every 4 hours to clean the magnetic bars.The outlet total chromium concentration in the pilot experiment can be stabilized to less than 0.5 mg/L.The demonstration project operated intermittently and continuously for 7 consecutive days at a flow rate of 10 m3/h,and the outlet total chromium concentration was less than 0.5 mg/L.The magnetic Fe3O4 nanoparticle production line with production capacity of 300 kg/day and a magnetic-chromium elution production line with a capacity of 300 kg/day were built.In addition,China’s Liaoning Province began to implement the "Liaoning Province Comprehensive Wastewater Discharge Standard DB21 1627-2008",which reduces the COD discharge standard to 50 mg/L.Traditional wastewater treatment technology is difficult to make the COD value of oil field produced water meet the latest discharge standards(COD<50 mg/L),or the cost is very high.This paper proposed an innovative mechanism for COD removal from oilfield produced water treated by traditional wastewater treatment technology with magnetic Fe3O4-IDA-Cu2+ nanoparticles.The magnetic separator was used in the continuous flow treatment experiment to remove COD,the COD removal efficiency could reach 66.7%,and the outlet COD value was stable and less than 50 mg/L.The spent magnetic Fe3O4-IDA-Cu2+ nanoparticles could be recycled and reused for 6 times,and the outlet COD concentration was stable less than 50 mg/L.更多还原