Adsorption of Heavy Metals by Biochar: Experimental and Literature Analyses

• Author / Creator

  Gu, Huile

• Biochar is a stabilized carbon with porous structure that can be used as an economical adsorbent for wastewater treatment. Since there are numerous types of biochars, it is important to understand how biochar characteristics influence adsorption performance by selecting or customizing biochars that are suitable for wastewater treatment. There is a large amount of wastewater containing low concentrations of heavy metals (e.g., cadmium and lead) produced daily all over the world. This research investigates the relationship between biochar characteristics and cadmium and lead adsorption performance in aqueous solutions both experimentally and using data collected from the literature.
  
  A batch adsorption experiment was conducted using non-activated and steam activated biochars made from wheat (Triticum aestivum) straw and cattle manure pellets. Cadmium nitrate (Cd(NO3)2) solutions with 0, 50, 75, 100, 125, 150, and 200 mg Cd/L were shaken with biochars until adsorption equilibrium to generate adsorption isotherms. The adsorption isotherms had poor fitting with Langmuir, Freundlich, Sips, and Dubinin-Radushkevich models, and the possible causes were discussed.
  To provide general suggestions about biochar selection for cadmium or lead removal from wastewater, data were collected from the literature on biochar adsorption in cadmium or lead solutions based on research papers published between 2011 and 2021. Biochar parameters (e.g., highest pyrolysis temperature, biochar pH, surface area, total pore volume, average pore size, ash content, atomic ratio of oxygen:carbon, atomic ratio of hydrogen:carbon), and adsorption model parameters (e.g., the maximum adsorption capacity, Qmax, of Langmuir model and the constant related to favourability of adsorption, 1/n, of Freundlich model) were collected from these research articles. Simple linear regression was used to investigate the relationship between biochar characteristics and adsorption capacity. Total pore volume, highest pyrolysis temperature, and biochar pH were identified as three potential predictors for cadmium adsorption capacity for wastewater remediation; however, this study did not find good predictors for lead adsorption capacity, suggesting biochar selection should be adjusted based on the target contaminant.

• Subjects / Keywords

  • Biochar
  • Heavy metal
  • Adsorption
  • Wastewater
  • Wastewater treatment
  • Steam activation
  • Cadmium
  • Lead
  • Adsorption isotherms

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-x06v-xg83

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.