About

Kaiwu Huang is an assistant professor in the Mining and Minerals Engineering department at Virginia Tech. His research interests include flotation simulation and modeling, mine tailings reprocessing, critical minerals beneficiation and extraction, paper recycling and deinking, and battery recycling. He holds a Ph.D. in Mining Engineering from Virginia Tech, earned in 2019, a master's degree from the same institution in 2015, and a bachelor's degree in Mineral Processing Engineering from China University of Mining and Technology (Beijing) in 2013. His work involves developing methods and technologies for mineral processing, resource recovery, and sustainable recycling practices. He is actively involved in research that advances understanding of fundamental mechanisms in mineral liberation and separation processes, contributing to innovations in mineral processing and resource management.

Research topics

• Composite material
• Materials science
• Chemistry
• Metallurgy
• Chemical engineering
• Mechanics
• Physics
• Nanotechnology
• Classical mechanics
• Chemical physics
• Thermodynamics
• Engineering
• Physical chemistry

Selected publications

• Overcoming Heterocoagulation Challenge in Selective Flotation Separation between Lithium Cobalt Oxide and Lithium Manganese Oxide

  SSRN Electronic Journal · 2025-01-01 · 2 citations

  preprintOpen access
  PublisherDOI

• Overcoming heterocoagulation challenge in selective flotation separation between lithium cobalt oxide and lithium manganese oxide

  Separation and Purification Technology · 2025-03-14 · 5 citations

  articleOpen access

  • Froth flotation can be used to separate and purify different spent cathode materials . • Hydroxamate-type collector can hydrophobize lithium cobalt oxide cathodes. • Heterocoagulation between different cathode materials is a challenge in separation. • Dispersants can be used to mitigate the heterocoagulation effect. • New flotation chemistries are developed to improve cathode materials recycling. Efficient separation of mixed cathode active materials from recycled Li-ion batteries is a prerequisite for both the successful direct recycling and hydrometallurgical recycling of spent lithium-ion batteries (LIBs). In this work, separation between lithium cobalt oxide (LCO) and lithium manganese oxide (LMO) was investigated using the froth flotation method. Sodium octanohydroxamate (OHA) was employed as the collector. It was found that individual LCO materials could be selectively hydrophobized by OHA and floated by air bubbles, while LMO materials could not be floated using OHA as the collector. Unfortunately, the flotation separation of a binary mixture of LCO and LMO in DI water was poor due to the heterocoagulation between these two cathode materials. With the addition of sodium metasilicate as the dispersant, the flotation separation of the two was significantly improved. The mechanism was investigated using ζ-potential measurements, SEM analysis, and DLVO force analysis. It was found that the ζ-potentials of both LCO and LMO were slightly negatively charged at a pH of 7 to 9, resulting in the heterocoagulation between the two cathode materials. The addition of sodium metasilicate increased the magnitude of negative ζ-potential and therefore improved particle dispersion and separation efficiency. The present work demonstrated the importance of dispersants in the separation of mixed cathode materials from Li-ion batteries.

  PublisherDOI

• Machine Learning and Analytical Approaches to Predict the Direct Aqueous Mineral Carbonation Efficiency of Olivine-Rich Rocks

  Energy & Fuels · 2025-09-08 · 1 citations

  article

  Direct aqueous ex situ mineral carbonation of CO2-reactive silicate minerals involves the reaction of silicate minerals with carbon dioxide (CO2) to form stable carbonate minerals. Previous studies have shown that the efficiency of mineral carbonation depends on both process variables and feed mineralogy. However, modeling tools for predicting carbonation efficiency remain limited. In this study, two categories of models were developed to predict mineral carbonation efficiency and CO2 uptake. These two approaches include (a) an analytical model based on a first-order reaction and (b) six data-based machine learning (ML) models. Olivine-rich rocks were used as the feed materials, and both the carbonation efficiency and the CO2 uptake were determined using a direct mineral carbonation protocol. The experimental results were compared with predictions from both analytical and ML models. The analytical model showed fair agreement with the experimental data. In contrast, the ML models demonstrated superior predictive performance, provided that a sufficient data set is available for training. Accuracy further improved when multiple models were integrated into an ensemble, yielding a root mean squared error value of 7.72. Feature importance analysis from ML models identified key processes and input variables influencing carbonation efficiency. This work demonstrates the utility of both analytical and ML models for predicting mineral carbonation efficiency and highlights the relative importance of process variables in the direct ex situ mineral carbonation.

  PublisherDOI

• Selective Extraction of Nickel and Cobalt from Serpentine Minerals Using Carbon-Negative Carbonation-Assisted Leaching Technology

  ACS Sustainable Resource Management · 2025-07-10 · 7 citations

  article

  Serpentine is a group of hydrous magnesium–iron phyllosilicate minerals that contain both nickel (Ni) and cobalt (Co). To date, the extraction of both Ni and Co from nickel-bearing serpentine minerals has been technologically challenging and economically unviable. In this work, a carbon-negative leaching technology was developed to extract Ni and Co from serpentine-rich rocks while simultaneously sequestering CO2 in the form of carbonate minerals. The conversion of serpentine to olivine using thermal activation was investigated under air and hydrogen environments. Lab-scale carbonation-assisted leaching trials showed that the hydrogen dehydroxylation process effectively transformed serpentine to olivine, increased the porosity of the feed minerals, and thereby enhanced the mineral carbonation efficiency. The carbonation efficiency reached 86%, with Ni and Co extraction rates of 80% and 75%, respectively, after 2 h. The carbonation efficiency was found to correlate strongly with the metal extraction efficiency, indicating that the limiting factor was the dissolution and release of divalent ions from the silicate mineral. Under optimal conditions, the activated serpentine mineral exhibited a CO2 uptake capacity of 357 kg per ton of feed, with approximately 2.63 kg of nickel and 0.43 kg of cobalt recoverable per ton of the feed. These findings illustrate the viability of hydrogen dehydroxylation coupled with carbonation-assisted leaching technology to unlock critical minerals from unconventional low-grade nickel ore resources.

  PublisherDOI

• Sulfate-activated mineral carbonation of olivine minerals with mechanisms explained by shrinking core models and by machine learning algorithm

  Minerals Engineering · 2024-10-28 · 14 citations

  articleOpen access
  PublisherOA PDFDOI

• Thin Liquid Film View and Shear Stress During the Sliding of Air Bubbles on Tilted Plates

  Langmuir · 2024-09-24 · 2 citations

  article

  The challenge when studying the impact and sliding of free-rising air bubbles on tilted surfaces is an experimental limitation in obtaining the film thickness of thin liquid film (TLF) during the bubbles' sliding on tilted surfaces. In this work, spatiotemporal evolution in the film thickness of the moving TLF between a sliding air bubble and a tilted plate was monitored by using a two-wavelength synchronized reflection interferometry microscopy (SRIM) technique. The evolution of the film thickness was directly determined from a timed series of monochromatic interference fringes recorded simultaneously at two different wavelengths. From the film thickness profile, a shear stress map at a given time was determined at different bubble sizes and inclination angles. Results showed that the film thickness of TLFs during the bubbles' sliding on tilted surfaces was in the range of 300-1200 nm, depending on bubble size and tilting angles. Sliding of air bubbles on tilted plates over a thin gap with a few hundred nanometers thickness yielded shear stress in the order of 10-50 Pa. Both the larger bubble size and higher tilting angles yielded a higher shear stress. Experimental results were quantitatively compared to numerical results obtained using the Reynolds lubrication theory. A good match between the two results was achieved. Numerical results suggested that a maximum shear stress exerted on a tilted plate occurred at a 25° tilting angle. This is the first time that the spatiotemporal evolution of TLF during bubbles' sliding on tilted surfaces has been achieved, and the shear stress exerted on the tilted surface has been directly determined.

  PublisherDOI

• Improving the performance of a low-grade porphyry copper ore flotation plant using a simulator that can predict grade vs. recovery curves

  Minerals Engineering · 2023-07-26 · 6 citations

  article
  PublisherDOI

• Solvent recovery from solvent-fine coal slurries by filtration and steam stripping

  Frontiers in Thermal Engineering · 2023-08-22

  articleOpen access

  Dewatering of fine coal is a significant industrial challenge with economic and environmental implications. Due to the lack of suitable dewatering technologies, fine coal particles are often discarded to waste impoundments, leading to substantial loss of valuable natural resources while creating environmental problems. The hydrophobic-hydrophilic separation (HHS) process is a unique solution to this problem. In this process, a recyclable solvent is used to simultaneously remove inorganic impurities (ash) and water from a run-of-mine fine coal slurry. A small amount of recyclable oil (or solvent) is added to a fine coal slurry so that the solvent can spontaneously displace the water from the surface of coal particles. The spent solvent is subsequently recovered and recycled in a closed loop. Here, we report the results obtained using two different solvents, i.e., pentane and hexane, to de-ash and dewater ultrafine coal and recover the spent solvent by filtration, followed by steam stripping. Most of the spent solvent can be recovered during the filtration step at 20 psig N₂ and at a 60 s filtration time. The residual solvent left in the cake was then recovered using steam under different conditions. The results showed that the residual solvent concentration could be reduced to <1,400 ppm after 10 s of steam stripping at 150°C and 15 psig.

  PublisherOA PDFDOI

• Improved Separation between Recycled Anode and Cathode Materials from Li-Ion Batteries Using Coarse Flake Particle Flotation

  ACS Sustainable Chemistry & Engineering · 2023 · 29 citations

  • Materials science
  • Composite material
  • Chemical engineering

  Separation between two recycled electrode active materials from spent Li-ion batteries by a conventional froth flotation method has been challenging due to similarity in their surface hydrophobicity. In this study, a new coarse flake particle flotation technology has been developed to separate the electrode active materials from Li-ion batteries. The new process separates the recycled electrode flake particles effectively at a size range of 212–850 μm by taking advantage of a significant difference in densities between the anode flake materials and cathode flake materials. At a feed size of 212 μm or less, a fraction of recycled cathode particles is floated in the froth layers resulting in a loss of cathode materials in the sink product. At a feed size of 850 μm or above, a small fraction of anode flakes becomes non-floatable, resulting in a decrease in the grade of cathode materials in the sink product. The mechanism has been investigated by induction time measurements, bubble–flake detachment, contact angle measurements, and force analysis. The anode flakes are more hydrophobic than cathode flakes, which is consistent with the result obtained from induction time measurements. A force analysis reveals that the critical size for electrode flake particles being attached to air bubbles varies with advancing contact angle and density. Maintaining a desirable feed size is essential to achieve an optimum separation performance. In this regard, a flotation column is superior to mechanical flotation cells in minimizing size reduction during the flotation process. Lab-scale column flotation trials showed that a good separation between anode and cathode flake particles has been achieved by column flotation with 98–99% purity of cathode flake materials in the sink product at a recovery rate of 96–99%. The present study demonstrates a new process in separating two electrode flake materials from spent Li-ion batteries.

  PublisherDOI

• Nanoscale Investigation into Dynamics of Thin Liquid Films during Bouncing and Attachment of Rising Air Bubbles on Hydrophilic and Hydrophobic Surfaces

  Langmuir · 2023-11-30 · 5 citations

  article

  Investigations on bouncing and attachment of free-rising air bubbles on hydrophobic surfaces have been limited to side-view, high-speed photography of the bubble-plate attachment process. In this work, an investigation of the dynamics as well as stability of thin liquid films (TLFs) between free-rising air bubbles and quartz surfaces was performed using a newly developed multiple-wavelength synchronized reflection interferometry microscopy (SRIM) technique. The effect of surface hydrophobicity on both the stability and critical rupture thickness of TLFs was investigated. Results showed that the TLF ruptured at a critical rupture thickness of 100–1000 nm or beyond during bubble’s impact on hydrophobic quartz surfaces. The critical rupture thicknesses varied depending on the surface hydrophobicity as well as surface asperity. A higher surface hydrophobicity, in general, contributed to a higher critical rupture thickness. In addition, the effect of n-octanol on the stability of the TLFs was investigated. Results showed that film stability increased with increasing the concentration of n-octanol, which was accompanied by a significant decrease in the critical rupture thickness. The present result illustrates, for the first time, the dynamics of TLFs on hydrophobic surfaces under a dynamic condition compared with previous studies under a quasi-equilibrium condition. The information revealed from the present work has a significant implication to many industrial applications, including froth flotation and other biological and semiconductor applications.

  PublisherDOI

Frequent coauthors

• Roe‐Hoan Yoon

  11 shared

• Lei Pan

  Michigan Technological University

  6 shared

• Aaron Noble

  Virginia Tech

  4 shared

• Alireza Hooshanginejad

  3 shared

• Ian M. Sherrell

  Virginia Tech

  3 shared

• Seung Woo Park

  2 shared

• Mohit Gupta

  2 shared

• Fatemeh Hamidzadeh

  University of Tehran

  2 shared