Fluoride Bio-Sorption Efficiency and Antimicrobial Potency of Macadamia Nut Shells

Area of Science:

• Environmental Science
• Materials Science
• Microbiology

Background:

• Fluoride contamination in surface water poses health risks.
• Developing sustainable and cost-effective water treatment methods is crucial.
• Macadamia nut shells (MNS) are an underutilized agricultural waste product.

Purpose of the Study:

• To evaluate the efficacy of macadamia nut shells (MNS) as a bio-sorbent for fluoride removal from water.
• To assess the antimicrobial properties of MNS against common waterborne pathogens.
• To investigate the adsorption mechanisms and thermodynamic feasibility of fluoride sorption by MNS.

Main Methods:

• Batch mode experiments were conducted to determine fluoride sorption efficiency.
• Well disc diffusion assay was used to investigate antimicrobial activity.
• Adsorption kinetics and isotherm data were analyzed using pseudo-second order and Langmuir models, respectively.
• Thermodynamic parameters were calculated to understand the sorption process.

Main Results:

• Maximum fluoride sorption capacity of 1.26 mg/g was achieved at specific conditions (5 mg/L initial fluoride, 0.5 g/100 mL adsorbent, 120 min contact time, pH 6).
• Pseudo-second order kinetics and Langmuir isotherm models best described the fluoride adsorption process, indicating chemisorption and monolayer adsorption.
• Fluoride sorption by MNS is a spontaneous and endothermic process.
• The bio-sorbent demonstrated good reusability over seven cycles using HCl for regeneration.
• MNS exhibited minimal antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae.

Conclusions:

• Macadamia nut shells show significant potential for fluoride bio-sorption from surface water.
• The adsorption process is spontaneous, endothermic, and follows chemisorption mechanisms.
• Enhancing the antimicrobial potency of MNS through doping with metal ions is recommended for comprehensive water treatment applications.