[Adsorption of Cd2+ on biochar from aqueous solution]

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Biochar derived from biomass shows potential for heavy metal adsorption.
• Cotton straw is an abundant agricultural waste suitable for biochar production.
• Cadmium (Cd2+) is a toxic heavy metal pollutant requiring effective remediation strategies.

Purpose of the Study:

• To investigate the adsorption performance of cotton straw biochar for cadmium ions (Cd2+).
• To determine the adsorption isotherm, kinetics, and the influence of environmental factors on Cd2+ adsorption.
• To evaluate the thermodynamic properties of the Cd2+ adsorption process.

Main Methods:

• Batch adsorption experiments were conducted.
• Adsorption isotherms (Langmuir, Freundlich) and kinetics (pseudo-second order) were analyzed.
• The effects of temperature, pH, and ionic strength on adsorption were systematically studied.
• Thermodynamic parameters, including free energy, were calculated.

Main Results:

• The Freundlich isotherm model provided a better fit for Cd2+ adsorption than the Langmuir model.
• Maximum adsorption capacities ranged from 9.738 to 10.71 mg/g as temperature increased from 288.15 K to 318.15 K.
• Adsorption is a spontaneous and endothermic process, with equilibrium reached within 40 minutes.
• Adsorption was significantly influenced by pH (optimal range 2-8) and decreased with increasing ionic strength.

Conclusions:

• Cotton straw biochar demonstrates significant potential for the removal of cadmium ions from aqueous solutions.
• The adsorption mechanism is complex, best described by the Freundlich model and pseudo-second order kinetics.
• Optimal adsorption conditions involve specific pH ranges and are favored by endothermic processes, suggesting biochar as a viable adsorbent for cadmium remediation.