中高硫煤NaOH H_(2)O_(2)电解脱硫机理研究

Investigating the mechanism of NaOH H_(2)O_(2)electrolytic desulfurization of medium-high sulfur coal

煤的含硫量过高会造成经济损失、环境污染,因此中高硫煤的利用受到了极大制约。为实现煤中硫的绿色高效脱除,研究设计了NaOH-H_(2)O_(2)电解脱硫体系,通过探究不同试验体系、不同试验因素对中高硫煤脱硫率的影响,确定了电解脱硫的最佳工艺条件;通过X-射线衍射(X-ray diffraction,XRD)、傅里叶变换红外光谱(Fourier Transform Infrared Spectrometer,FT-IR)和X-射线光电子能谱(X-ray Photoelectron Spectroscopy,XPS)分析各试验体系下煤中矿物质组分、官能团及硫元素形态变化以探究电解脱硫机理。NaOH-H_(2)O_(2)电解脱硫体系的最佳反应条件是:NaOH浓度为3 mol/L、电流强度为0.75 A、氧化剂30%H_(2)O_(2)的体积为25 mL、电解温度为40℃、电解时间为1 h。脱硫机理为:OH^(-)、H_(2)O_(2)在电解过程中生成了高活性的自由基O^(-)和·OH等,可促使煤中黄铁矿类无机硫被氧化成硫酸盐并进行脱除;硫醇、硫醚和噻吩类有机硫氧化成(亚)砜后,在碱性环境中会被水解为硫酸盐或磺酸类化合物并进行脱除。

To mitigate the economic loss and environmental pollution associated with the use of medium to high sulfur coal,and to achieve efficient and environmentally friendly desulfurization,we designed the NaOH-H_(2)O_(2)electrolytic desulfurization system for the removal of sulfur from coal.Through investigating the impact of various experimental systems and factors on desulfurization rates,we determined the optimal experimental conditions.We employed X-ray Diffraction(XRD),Fourier Infrared Spectroscopy(FT-IR),and X-ray Photoelectron Spectroscopy(XPS)to analyze the functional group ratio and sulfur content in coal,thereby proposing a desulfurization mechanism.The experimental results are as follows:The optimal conditions for the NaOH-H_(2)O_(2)electrolytic desulfurization system were determined as follows:NaOH concentration of 3 mol/L,current intensity of 0.75 A,30%H_(2)O_(2)volume of 25 mL as an oxidizer,an electrolytic temperature of 40℃,and an electrolytic time of 1 hour.Under these optimal conditions,the desulfurization rate of coal reached its peak at 38.94%.Furthermore,when compared to the NaOH-H_(2)O_(2)immersion desulfurization system,the desulfurization rate increased by 27.37%with the application of an electric field.Additionally,compared to the NaOH electrolytic desulfurization system,the desulfurization rate increased by 8.98%after the addition of H_(2)O_(2).The primary functional groups in the coal remained unchanged;however,the content of sulfur-containing groups and ash were significantly reduced following treatment with the NaOH-H_(2)O_(2)electrolytic desulfurization system.Moreover,the increase in—OH groups in coal could create favorable conditions for the oxidation and breaking of organic sulfur bonds.The desulfurization mechanism of the NaOH-H_(2)O_(2)electrolytic desulfurization system is as follows:During electrolysis,OH^(-)and H_(2)O_(2)generate highly active free radicals O^(-)and·OH.These free radicals can enhance the oxidation effect and promote the conversion of pyrite inorganic sulfur in coal to sulfate,effectively facilitating its removal.Furthermore,mercaptan,thioether,and thiophene organic sulfur compounds are oxidized to sulfoxides and sulfones,which are subsequently hydrolyzed to form sulfates or sulfonic acids in an alkaline environment.