In Situ Biocidal Nanoparticles on RO Membranes

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Solution Overview

Problem

Reverse osmosis membrane systems face challenges with biofouling due to bacterial biofilms, which reduce water flux and salt rejection, and existing methods for preventing biofilm formation are either ineffective or costly, particularly for thin-film composite polyamide membranes.

Innovation Solution

A method for in situ formation of biocidal metal nanoparticles, such as silver and copper, on the membrane surface by reacting a metal salt solution with a reducing agent, allowing for uniform coverage and strong antibacterial activity without significantly impacting membrane properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If disinfectants and oxidants such as chlorine are used to inactivate bacteria in feed water, then bacterial inactivation is improved, but thin-film composite polyamide membranes degrade

Engineering Contradiction:

Improvebacterial inactivationVSAvoidmembrane integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by incorporating biocidal metal nanoparticles specifically at the membrane surface where bacterial contact occurs, rather than using bulk chemical disinfectants that would degrade the entire membrane. This localized biocidal action provides bacterial protection while preserving membrane integrity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses biocidal metal nanoparticles as an intermediary substance that mediates between the need for bacterial inactivation and membrane protection. These nanoparticles provide antimicrobial activity without the degrading effects of chlorine or other oxidants, serving as a safer alternative agent.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If metal nanoparticles are added directly into feed water, then biofouling control is improved, but metal consumption increases and cost increases

Engineering Contradiction:

Improvebiofouling controlVSAvoidmetal consumption

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies preliminary action by pre-loading biocidal metal nanoparticles onto the membrane surface during fabrication or activation. This preliminary incorporation ensures that the nanoparticles are positioned where they are most needed, eliminating the need for continuous metal addition to feed water and reducing overall metal consumption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements self-service by designing the membrane to inherently possess biocidal properties through integrated metal nanoparticles. The membrane serves its own biofouling protection function without requiring external chemical additions, making the system self-sufficient and reducing metal consumption.

Inventive Principle:

Principle #25Self-service

3Reliability

If biocidal metal nanoparticles are loaded on membrane surface, then antibacterial activity is improved, but membrane fabrication complexity increases

Engineering Contradiction:

Improveantibacterial activityVSAvoidmembrane fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies merging by combining the membrane formation process with the biocidal nanoparticle incorporation process into a single integrated step. By adding metal salt precursors to the feed side of the membrane during or after fabrication, and then reducing them in situ, the patent eliminates separate nanoparticle loading steps and reduces manufacturing complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces mechanical or physical nanoparticle deposition methods with chemical reduction processes. By using chemical reduction of metal salts directly on the membrane surface, the patent achieves nanoparticle incorporation without complex mechanical deposition equipment or multi-step physical processes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The method effectively reduces bacterial attachment and biofilm formation by 75% for silver nanoparticles and 90% for copper nanoparticles, maintaining membrane permeability and surface properties while providing a cost-effective and repeatable solution for biofouling control.

Implementation Method 1

reacting a reducing agent solution with the active layer of the membrane and the thin layer of the biocidal metal salt solution thereby forming a biocidal metal nanoparticle-modified membrane

Methodology Applied

Scientific EffectChemical reduction: Reduction

Data Source

PatentUS10179312B2In situ formation of biocidal metal nanoparticles on thin-film composite reverse osmosis membranes for biofouling mitigation

Publication Date: 2019.01.15 YALE UNIVERSITY

AI summary

The present invention relates to a method including reacting a solution of a salt of a biocidal metal with an active layer of water purification membrane, discarding the biocidal metal salt solution such that a thin layer of the biocidal metal salt solution remains on the membrane surface, reacting a reducing agent solution with the active layer of the membrane and the thin layer of the biocidal metal salt solution thereby forming a biocidal metal nanoparticle-modified membrane, removing the reducing agent solution, and rinsing the biocidal metal nanoparticle-modified membrane.