Effect of Hydrogen Peroxide Concentration on Zinc Ion Adsorption by Human Hair

Abstract

Introduction: The global issue of heavy-metal pollution has extensive consequences for both the environment and human health. Traditional cleanup approaches usually fall short, encouraging the search for innovative methods that are both effective and sustainable. This study investigates the potential use of keratinous materials, specifically human hair, as a potential solution for heavy metal contamination.

Methods: Stock Zn(NO3)2·6H2O solutions were prepared. Collected human hair was cleaned, rinsed, air-dried, and cut into small pieces. Hair was treated by soaking at pH 9.0 for 24 hours in H2O2 of concentrations ranging from 0% to 3%, then filtering and drying. The treated hair was placed in tubes with the zinc solution. Afterward, the hair was filtered, solutions were stored, and EDTA titration begins after an indicator is introduced. The volume of EDTA solution was recorded, and this process was repeated for the remaining solutions following a control titration. The adsorption capacity was calculated using metal ion concentrations, allowing for a quantitative comparison of biosorption efficiency across treatments.

Results: Notably, as the hydrogen peroxide concentration increased, a gradual decrease in the required EDTA volume was recorded, thus suggesting that lower residual zinc concentrations are present.

Discussion: The control untreated hair had a biosorption capacity of 1.05 mg/g, whereas the 3% treated hair had a biosorption capacity of 12.95 mg/g. This indicates a 91.89% percent increase in biosorption capacity from the control to the 3% treated hair. Thus, the greater the hydrogen peroxide concentration is, the more zinc ions would be absorbed by the hair; so, its biosorption capacity would increase.

Conclusion: The idea of using hair as a biosorbent is gaining traction; however, it is still mostly unexplored. This study demonstrates that increasing hydrogen peroxide concentration enhances the zinc ion adsorption capacity of human hair, likely due to oxidative changes increasing the availability of binding sites, therefore supporting the potential application of treated keratinous waste for low-cost high-yield metal remediation systems. Future research may explore different biological substrates (e.g., wool, feathers, etc.) or optimize treatment conditions (e.g. pH, metal substrate, etc.) to further increase adsorption efficiency.