Evaluation of modified boehm titration methods for use with biochars

Area of Science:

• Environmental Chemistry
• Materials Science

Background:

• The Boehm titration is widely used to quantify organic functional groups on carbon materials.
• Biochar's unique properties, like higher ash content and carbon solubility, challenge the reliability of standard Boehm titration.
• Accurate characterization of biochar functional groups is crucial for understanding its applications.

Purpose of the Study:

• To evaluate the reliability of three modified Boehm titration methods for biochar analysis.
• To identify the most accurate combination of methods and reactants for quantifying biochar functional groups.
• To address the limitations of traditional Boehm titration when applied to biochar.

Main Methods:

• Tested three Boehm titration variations: sparge method, barium method, and cartridge method.
• Utilized seven biochars and one reference carbon black for method validation.
• Assessed method performance across different pK ranges to identify biases.

Main Results:

• No single Boehm titration method proved unbiased for all pK ranges and reactants.
• The cartridge method exhibited bias across all tested pK ranges.
• A combined approach using the sparge method (low pK) and barium method (high pK) showed no evidence of bias.

Conclusions:

• A combination of the sparge and barium methods is recommended for reliable quantification of biochar functional groups.
• Ash removal and prevention of dissolved organic compound interference are critical for accurate results.
• Further research is needed to fully validate these findings for diverse biochar types.