Preparation of Ti-based Yb-doped SnO2–RuO2 electrode and electrochemical oxidation treatment of coking wastewater

In this study, the Ti/SnO₂–RuO₂ electrodes with different Yb contents were prepared by sol–gel method and thermal decomposition method, and the surface morphology and crystal structure of the electrodes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD), the electrochemical properties of the electrodes were tested by linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The electrochemical oxidation device was constructed with Yb-doped Ti/SnO₂–RuO₂ electrode as the anode and titanium plate as the cathode, and the electrochemical oxidation effect and product changes of the anode on coking wastewater were investigated. The results show that the surface of the electrode is flat with high crystallinity of SnO₂ and RuO₂ crystals at 1.5% Yb doping, and the LSV and CV curves indicate that the Yb doping of 1.5% increases the oxygen precipitation potential and electrocatalytic oxidation activity of the electrode. When the electrode with Yb doping of 1.5% is the anode with current density of 10 mA/cm² electrochemical oxidation time of 30 min, the electrode can remove chemical oxygen demand (COD) up to 85.06%, total organic carbon (TOC) up to 60.59% and UV₂₅₄ from 1.594 to 0.507 for coking wastewater. Gas chromatography (GC–MS), UV–vis and three-dimensional fluorescence results of coking wastewater before and after treatment show that large toxic substances in coking wastewater are degraded to low toxic organic substances, and most soluble organic substances are degraded and transformed. This study provides the possibility of basic research for the engineering practice of electrochemical oxidation for the treatment of coking wastewater.     

Experimental study on the creep behavior of frozen clay with thermal gradient

Thermal gradient is one of the main features in frozen engineering, especially in artificial frozen wall (AFW) in deep alluvium. This paper investigated the creep behaviors of frozen soil with thermal gradient. A series of uniaxial creep tests were carried out on frozen saturated clay under various thermal gradients and creep stresses by GFC (freezing with non-uniform temperature without experiencing K₀ consolidation) method. Two stages were observed during the whole creep process, i.e., instantaneous elastic deformation and decaying creep deformation. Radial creep deformation of ε₃ almost increases linearly with an increase in axial creep deformation of ε₁, and the slope of ε₃–ε₁ curve increases as the thermal gradient (or creep stress) increased. Long-term strength decreases as the thermal gradient (or the creep time) increased. Considering the correction equation on thermal gradient, the generalized Kelvin model consisting of one Hooke element and two Kelvin elements has been developed to describe the axial creep deformation. The validity of the model is verified by comparing its calculated results with the results of creep tests under both low and high thermal gradient. It is found that the axial creep deformation behavior of frozen saturated clay can be represented by generalized Kelvin model, and the proposed model reflects thermal gradient effects to the creep deformation well.