Iron-coated nutshell waste bioadsorbents: Synthesis, phosphate remediation, and subsequent fertilizer application
Chandra M Tummala1, Mohammed Dardona1, Sai Praneeth1
1Department of Civil and Environmental Engineering, Wayne State University, 5050 Anthony Wayne Dr., Detroit, MI, 48202, USA.
Environmental Research
|October 23, 2023
Summary
This study developed iron-coated pistachio and walnut shells to capture phosphate from wastewater, demonstrating their potential as slow-release fertilizers. The novel biosorbents effectively removed phosphate and enhanced plant growth, promoting circular economy goals.
Area of Science:
- Environmental Science
- Materials Science
- Agricultural Science
Background:
- Freshwater nutrient pollution, particularly from phosphate, is a growing global concern, leading to harmful algal blooms.
- Effective phosphate recovery is crucial for preventing eutrophication and conserving finite phosphate reserves.
- Biodegradable biosorbents offer potential for phosphate removal, but their dual role as slow-release fertilizers requires investigation.
Purpose of the Study:
- To develop novel biodegradable biosorbents from agricultural waste for phosphate capture.
- To evaluate the adsorption capacity and performance of iron-oxide-coated shells for phosphate removal.
- To assess the potential of phosphorus-loaded biosorbents as slow-release fertilizers for plant growth.
Main Methods:
- Coating pistachio and walnut shells with iron oxides to create novel biosorbents.
- Conducting batch and column experiments to determine phosphate adsorption capacities.
- Utilizing advanced characterization techniques (SEM, BET, XRD) for surface analysis.
- Performing sequential release experiments and Mehlich-3 extraction to assess phosphate bioavailability.
- Evaluating plant growth promotion using nutrient priming with phosphate-loaded biosorbents.
Main Results:
- Successful coating of shells with hematite, increasing surface area and roughness.
- Phosphate removal capacities of 12.63 mg/g for coated pistachio shells and 9.25 mg/g for coated walnut shells.
- Phosphate sorption data best fitted Freundlich isotherm and pseudo-second-order kinetics, indicating complex uptake mechanisms.
- Sequential release experiments showed both fast and slow phosphate desorption components.
- Over 90% of released phosphate was bioavailable for plant uptake, with a >43% increase in corn shoot growth.
Conclusions:
- Iron-coated pistachio and walnut shells are effective, low-cost biosorbents for phosphate removal from wastewater.
- These biosorbents function as viable slow-release fertilizers, utilizing agricultural waste and aiding phosphorus recovery.
- The developed technology supports zero-waste, cyclical economic goals by transforming waste into valuable resources.
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