Cr-Based MOF Flocculation for Harmful Algae Removal Without Toxin Release

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Solution Overview

Problem

Existing flocculants for harmful algal blooms (HABs) are either inefficient, environmentally harmful, or cause secondary pollution, and do not effectively remove microcystin toxins without inducing cell lysis.

Innovation Solution

Utilizing a chromium-based metal-organic framework (MOF), specifically NH2-MIL-101(Cr), as a flocculant to aggregate and precipitate harmful algae like Microcystis aeruginosa in water sources, achieving high flocculation efficiency and stability across various pH conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional flocculants (e.g., NZVI, polymeric flocculants, chitosan) are used to remove harmful algae, then flocculation efficiency is improved, but they cause secondary pollution through corrosion, inherent toxicity, or cell lysis releasing intracellular toxins

Engineering Contradiction:

Improveflocculation efficiencyVSAvoidsecondary pollution

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention uses a core-shell structured composite material consisting of nanoscale zero-valent iron (NZVI) cores coated with magnesium hydroxide (Mg(OH)2) shell. This composite structure combines the flocculation capability of NZVI with the protective and environmentally benign properties of Mg(OH)2, resolving the contradiction between efficiency and environmental safety

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention converts the potentially harmful NZVI material into a safe flocculant by coating it with Mg(OH)2. The coating transforms the toxic properties of bare NZVI into beneficial properties: protection from corrosion, reduced toxicity to cyanobacterial cells, and prevention of secondary pollution while maintaining flocculation efficiency

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Productivity

If some flocculants are used to remove harmful algae, then algae removal is achieved, but they induce cell lysis of cyanobacteria releasing intracellular toxins into water

Engineering Contradiction:

Improvealgae removal efficiencyVSAvoidtoxin release

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The Mg(OH)2 coating on NZVI converts a potentially harmful effect (cell lysis and toxin release) into a beneficial outcome by providing a gentle flocculation mechanism that aggregates cyanobacterial cells without damaging their integrity, thus preventing toxin release while achieving efficient removal

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If certain flocculants are used for algae sedimentation, then removal process is initiated, but they require long processing times and have low efficiency

Engineering Contradiction:

Improveremoval efficiencyVSAvoidprocessing time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The invention segments the flocculation process into efficient stages by using nanoscale NZVI particles with high surface area to volume ratio, which accelerates the flocculation kinetics and reduces processing time while maintaining high removal efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the physical and chemical parameters of the flocculant by using nanoscale zero-valent iron with specific size range and Mg(OH)2 coating thickness, which optimizes the flocculation speed and efficiency, reducing the required processing time compared to conventional flocculants

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

NH2-MIL-101(Cr) demonstrates >95% flocculation efficiency within 1.5 hours, outperforming conventional flocculants like ferric chloride and chitosan, and maintains stability in freshwater environments, preventing toxin release and secondary pollution.

Implementation Method 1

The use of flocculation followed by gravity sedimentation is one potential method for the removal of microalgae in natural water

Methodology Applied

Scientific EffectFlocculation: Flocculation

Implementation Method 2

Flocculants allow algae to adhere to each other, generating flocs, and thereby facilitating the sedimentation and removal of algae

Methodology Applied

Scientific EffectGravity sedimentation: Sedimentation

Data Source

PatentUS12466748B2Method of floculation using a metal-organic-framework

Publication Date: 2025.11.11 CITY UNIVERSITY OF HONG KONG

AI summary

The present disclosure relates to a method of flocculation, wherein harmful cyanobacteria are flocculated via metal-organic framework, and wherein the metal-organic framework comprises chromium, which is environmentally friendly. Water-stable Cr(III)-based MOFs, structured as NH2-MIL-101, remove harmful algal blooms, such as Microcystis aeruginosa, from natural water sources by promoting flocculation. NH2-MIL-101(Cr) MOFs efficiently remove harmful algae from water without creating secondary pollution and without causing the harmful algae to release intracellular toxins.