Phosphate Recovery from Urine-Equivalent Solutions for Fertilizer Production for Plant Growth

Area of Science:

• Environmental Chemistry
• Materials Science
• Sustainable Engineering

Background:

• Centralized wastewater treatment plants yield highly diluted phosphate streams (<10 ppm).
• Decentralized wastewater systems offer concentrated phosphate streams (∼500 ppm), suitable for recovery.
• Phosphate recovery from wastewater aligns with circular economy principles.

Purpose of the Study:

• To demonstrate the feasibility of phosphate recovery from concentrated aqueous solutions.
• To evaluate Mg-Fe layered double hydroxide (LDH) as a phosphate adsorbent and fertilizer precursor.
• To assess the recyclability of the adsorbent in a semicontinuous process.

Main Methods:

• Utilized Mg-Fe layered double hydroxide (LDH) for phosphate adsorption from simulated wastewater.
• Investigated phosphate adsorption mechanisms, including surface complexation and electrostatic attraction.
• Performed consecutive adsorption/desorption cycles to evaluate adsorbent stability and recyclability.
• Tested the recovered phosphate as a fertilizer in plant growth media.

Main Results:

• Mg-Fe LDH effectively adsorbs phosphate from high-concentration solutions (∼500 ppm).
• Adsorption occurs via a combination of surface complexation and electrostatic attraction.
• The LDH adsorbent demonstrated stability and recyclability over multiple adsorption/desorption cycles.
• Recovered phosphate successfully enhanced plant growth in deficient media.

Conclusions:

• Phosphate recovery from concentrated wastewater streams is feasible using Mg-Fe LDH.
• The recovered phosphate can be effectively utilized as a plant fertilizer.
• This process supports a circular economy by transforming waste into a valuable resource.