Watermelon rind: agro-waste or superior biosorbent?

Area of Science:

• Environmental Science
• Environmental Chemistry
• Materials Science

Background:

• Heavy metal contamination in water poses significant environmental and health risks.
• Developing cost-effective and sustainable biosorbents is crucial for water remediation.
• Agricultural waste materials offer potential as low-cost biosorbents.

Purpose of the Study:

• To investigate the biosorption of copper (Cu), zinc (Zn), and lead (Pb) using watermelon rind.
• To determine the optimal pH and assess the biosorptive capacity for these metals.
• To evaluate the reusability and metal recovery potential of the watermelon rind biosorbent.

Main Methods:

• Batch biosorption experiments were conducted in a well-stirred system.
• The influence of pH on metal uptake was studied.
• Biosorption equilibrium was modeled using the Langmuir isotherm, and kinetics were analyzed with pseudo-first-order and pseudo-second-order models.
• Desorption and reusability were tested using NaOH solution.

Main Results:

• Optimal pH for Cu, Zn, and Pb biosorption was determined to be 5.0, 6.8, and 6.8, respectively.
• Watermelon rind demonstrated high efficiency for Pb removal (up to 99%) at low concentrations.
• Maximum biosorptive capacities were 6.281 mg/g for Cu, 6.845 mg/g for Zn, and 98.063 mg/g for Pb.
• Langmuir isotherm and pseudo-second-order kinetic models best described the data.
• NaOH was an effective eluent, and the biosorbent maintained high removal efficiency (up to 99%) after multiple cycles.

Conclusions:

• Watermelon rind is a highly effective, reusable, and economical biosorbent for removing Pb, Cu, and Zn from water.
• Ion exchange and micro-precipitation are the primary mechanisms involved in metal biosorption.
• This agricultural waste presents a sustainable solution for heavy metal remediation in wastewater.