Dual interface-engineered bone char seeds for calcium phosphate crystallization.

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Conventional phosphate removal methods use external chemicals, raising sustainability concerns.
• Crystallizing phosphate with naturally present calcium (Ca²⁺) is a promising alternative but faces high nucleation energy barriers.
• High nucleation energy barriers (∆G*) hinder spontaneous crystal formation, limiting efficiency.

Purpose of the Study:

• To develop a novel method for efficient phosphate removal from secondary effluent.
• To overcome the high nucleation energy barrier in phosphate crystallization using engineered seeds.
• To investigate the potential of bone-derived char as a sustainable phosphate capture material.

Main Methods:

• Developed bone-derived char seeds to reduce interfacial energy for hydroxyapatite nucleation.
• Engineered dual interfaces (bone char-hydroxyapatite and bone char-liquid) to lower nucleation energy barriers.
• Utilized a fixed-bed column with bone char to treat actual secondary effluent and assess phosphate retention capacity.

Main Results:

• Bone-derived char seeds decreased effective interfacial energy by 71.1%, lowering ∆G* by a factor of 41.5.
• Achieved nucleation rates comparable to high-pH conventional methods in near-neutral effluent.
• Demonstrated a phosphate retention capacity exceeding 48.8 g P/kg of bone char over 20,000 bed volumes.

Conclusions:

• Bone-derived char seeds effectively reduce nucleation energy barriers, enabling efficient, sustainable phosphate crystallization.
• The unique structure of bone char optimizes interfacial properties for accelerated hydroxyapatite formation.
• This technology offers a sustainable, high-capacity solution for deep phosphate removal with broad global applicability.