In Malaysia, a tropical nation celebrated for its varied fruit selection, fruit waste notably contributes to municipal solid waste. Despite a consistent increase in tropical fruit production, reaching over 1.45 million tonnes in 2017 due to expanded land use and productivity enhancements, agricultural and food waste remain significant contributors in developing countries.
The prevalent fruit peel waste presents a valuable reuse opportunity. Associate Professor Dr Low Wen Pei and her team from INTI International University’s Faculty of Engineering and Quantity Surveying (FEQS) researched to transform this often-discarded agricultural waste into a viable material for treating contaminated water. Their study emphasises the effectiveness of fruit peels from rambutan, watermelon, and mango in absorbing iron, copper, and zinc after undergoing specific treatment processes.
The research, titled ‘Adsorption of Zinc, Copper, and Iron from Synthetic Wastewater using Watermelon (Citrullus lanatus), Mango (Mangifera Indica L.), and Rambutan Peels (Nephelium Lappaceum L.) as Biosorbents,’ used sodium hydroxide (NaOH)- treated peels to remove these metals from synthetic wastewater.
Associate Professor Dr Low Wen Pei and her team from INTI International University’s Faculty of Engineering and Quantity Surveying (FEQS) found that pretreated fruit peels from rambutan, watermelon, and mango effectively adsorb zinc, copper, and iron ions from water. This suggests their potential as affordable and eco-friendly solutions for heavy metal removal in developing nations with water contamination issues.
AP Dr Wen remarked, “This study delves into the adsorption capacity of treated fruit peels, specifically those from rambutan, watermelon, and mango, for extracting iron, copper, and zinc metal ions from water. Given that fruits serve as raw materials for various products, the inevitable waste includes the fruit peels and seeds.”
She further noted, “Despite its abundant water resources, Malaysia faces a water crisis due to growing demand and insufficient supply, poor water management, and ineffective basin planning. High-cost, high-tech water treatment solutions may not be feasible for all communities, highlighting the need for low-cost, alternative materials for treating contaminated water.”
The study found that the adsorption of heavy metal ions (iron, copper, and zinc) on the peels was generally favourable to the Langmuir isotherm, with exceptions for zinc on watermelon peels and copper on rambutan peels, which adhered to the Freundlich isotherm. This indicates a multilayer adsorption process.
“Fruit waste peels have emerged as a cost-effective alternative for removing metal ions from water, offering an economical solution,” AP Dr Wen concluded.
The application of mango, rambutan, and watermelon peels as adsorbents for copper, iron, and zinc is relatively novel. These metals were chosen because they are common in fertilisers and pesticides, major pollutants in rivers near agricultural activities.
Given the reliance of developing countries on agriculture for economic stability, employing heavy metals as adsorbents is particularly beneficial. Unlike wealthier nations with more resources, these alternative adsorbents are poised for increased utilisation in developing countries, often constrained by budget.