A novel graphene/geopolymer nanocomposite was firstly synthesized by using two-dimension graphene (GR) and alkali-activated granulated blast furnace slag-based geopolymer (ASG), and used to degrade simulation dye effluents. Diffuse reflectance UV–Vis spectrum indicated that the maximum absorption wavelength of the nanocomposite (GR/ASG) is red-shift to the visible region. The pore diameter distribution results of the GR/ASG1 sample showed that at least 89.59% of pore volume centralized on the region of 2–50 nm. The photocatalytic degradation efficiencies of samples for methyl violet dye is in the order of GR/ASG1 > GR/ASG2 > ASG under the irradiation of UV. The GR/ASG1 photocatalyst exhibited the highest degradation efficiency and approached to 91.16% for 110 min. The photocatalytic degradation reaction belongs to the second-order reaction kinetics.

In consideration of offshore oil spill accidents, a mechanical method is a kind of widely used treatment methods to recover spilled oil at sea. It also has the advantages of low cost, convenient use, and environmental friendliness. In order to improve the recovery efficiency and oil content of liquid recovered, a novel mechanical spilled oil recovery philosophy coupling surface vortex and hydrocyclone separation was proposed, and a small-scale prototype was manufactured. Medium crude from Bohai oil field was applied as spilled oil to test the recovery property of the prototype skimmer. The experiment results show that the novel skimmer is able to recover spilled oil effectively on the sea surface and speed up the process of recovery. Pressure of overflow pipe is sensitive to pump frequency, flow rate of inlet, and split ratio. In addition, oil content at the overflow port is influenced by spilled oil amount on the surface and split ratio. Besides, linear relationship is found between the recovery efficiency and the split ratio. The experimental study can provide a technical reference for the treatment of a small amount of spilled oil on the water surface and also has great significance for the design of spilled oil recovery equipment.

The vast majority of current research on hydrocyclone field centrifugal separation focuses on low concentration fluids having volume fraction less than 3%. For high-concentration fluids having volume fractions greater than 10%, which are often encountered in engineering, the law governing particle motion and the classification mechanism are still unclear. In order to gain insights into the interaction between fine particles in the high concentration hydrocyclone field and to improve the hydrocyclone separation performance of these particles, a Dense Discrete Phase Model (DDPM) of the Euler-Eulerian method under the Ansys Fluent 14.5 software was employed. Numerical simulations were carried out to study the characteristics of the hydrocyclone field of dense particles and the influence of parameters, such as the diameter of the overflow outlet, diameter of the underflow outlet, and material concentration, on separation performance. The trajectories and separation efficiencies of two kinds of fine particles with different densities and six different particle sizes at high concentration were obtained. The results show that for the hydrocyclone classification of high-concentration fine particles, particles with large density and small particle size are more likely to enter the internal cyclone and discharge from the overflow. Particles with small density and large particle size are more likely to enter the external cyclone and discharge from the underflow. The research results of this topic could provide a feasible reference and theoretical basis for the centrifugal separation of high-concentration fine particle fluid.

Traditional hydrocyclones can be used for the concentration of sewage-containing sediments, but the low underflow concentration and the high content of fine particles result in a large subsequent dehydration workload. This study aimed to investigate the effect of columnar hydrocyclone column height on separation performance and the change in the internal flow field after the underflow orifice of the hydrocyclone was closed, so as to provide a theoretical basis for improving the ability to treat the sewage of the hydrocyclone. Numerical simulation was used to examine the change in the separation performance of the hydrocyclone and the effect of column height on the separation performance of the hydrocyclone in the case of the closed underflow orifice during intermittent discharging. The results indicate that a proper increase in column height was beneficial to improve the separation performance of the hydrocyclone. With the increase in the closing time of the underflow orifice, the particle content at the bottom of the hydrocyclone increased significantly. The experiment proves the feasibility of the intermittent discharge method in practice, and this working method can effectively increase the underflow concentration.