Amide Cleaning Liquid for Aromatic Polyamide RO Membrane Foulant Removal
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Solution Overview
Problem
Aromatic polyamide RO membranes used in water treatment often become fouled by inorganic and organic substances, leading to degradation in permeation flux, pressure difference, and salt rejection rate, which conventional cleaning agents fail to adequately address, especially when dealing with foulants like polyalkylene glycol, nonionic surfactants, saccharides, or proteins.
Innovation Solution
An alkaline liquid containing an aliphatic or aromatic amide compound, optionally combined with an anionic surfactant and an N-containing saturated heterocyclic compound, is used to effectively remove foulants from aromatic polyamide RO membranes by penetrating and detaching them under alkaline conditions, enhancing cleaning efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cleaning agents (alkaline agents, surfactants, chelating agents) are used to clean aromatic polyamide RO membranes, then the membranes can be cleaned under alkaline conditions, but the cleaning effectiveness is insufficient for heavily fouled membranes containing inorganic substances and high molecular weight organic substances
Solution Approach 1:
The patent changes the chemical composition parameters of the cleaning agent by introducing organic solvents (alcohols, ethers, esters, ketones, amides) with specific molecular weights and structures. These solvents have different polarities and solubility parameters that enable them to effectively dissolve and remove high molecular weight organic foulants and inorganic deposits that conventional alkaline agents cannot adequately clean, thereby improving cleaning effectiveness and membrane performance recovery
Solution Approach 2:
The patent creates a composite cleaning agent system that combines conventional alkaline agents (sodium hydroxide, potassium hydroxide) with specifically selected organic solvents. This composite formulation leverages the synergistic effects of the alkaline environment and the solvent properties of organic compounds to enhance the overall cleaning capability, allowing effective removal of both organic and inorganic foulants from the membrane surface
2Reliability
If sodium hypochlorite is used to clean microorganisms and organic substances, then cleaning effectiveness against biological foulants is high, but aromatic polyamide RO membranes cannot be used because they have low resistance to chlorine
Solution Approach 1:
The patent extracts and removes the harmful chlorine component from the cleaning system. Instead of using sodium hypochlorite (which contains chlorine), the patent employs organic solvents and alkaline agents that do not contain chlorine, thereby eliminating the risk of chlorine damage to the aromatic polyamide membrane while maintaining cleaning effectiveness against microorganisms and organic substances
Solution Approach 2:
The patent introduces organic solvents as intermediary substances that can effectively interact with and remove organic foulants and microorganisms without causing damage to the membrane. These solvents act as mediators between the cleaning objective and the membrane material, achieving fouling removal while preserving membrane integrity
3Reliability
If organic solvents like ethanol or ethylene glycol monomethyl ether are used as cleaning agent components, then cleaning effectiveness is improved, but ethanol and methanol have high flash points making the method not practical
Solution Approach 1:
The patent carefully selects organic solvents with specific physical and chemical parameters, particularly focusing on flash point, molecular weight, and solubility characteristics. By choosing solvents with appropriate parameters (lower flash points than ethanol/methanol but still safe, and optimal solubility for different foulants), the patent achieves effective cleaning while maintaining practical safety and ease of use
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 proposed cleaning solution significantly improves the recovery of permeation flux and salt rejection rate of fouled RO membranes, outperforming conventional cleaning agents by achieving higher cleaning effectiveness and maintaining salt rejection rates close to those of fresh membranes.
Implementation Method 1
an aliphatic amide and/or an aromatic amide... enable highly effective removal of foulants adhered on an aromatic polyamide RO membrane
Implementation Method 2
cleaning under alkaline conditions where the pH value is 10 or more
Implementation Method 3
Surfactant (e.g., sodium lauryl sulfate)
Data Source
Figure 1~2
AI summary
Provided is an agent and a liquid for cleaning an RO membrane to remove effectively foulants that can not be sufficiently removed with conventional cleaning agents when an RO membrane particularly an aromatic polyamide RO membrane has been used for water treatment and has become fouled resulting in degradation of performance such as permeation flux, pressure difference, and salt rejection rate. The agent for cleaning an RO membrane includes an aliphatic amide and/or an aromatic amide. Also provided is a method for cleaning an RO membrane with the cleaning agent or the cleaning liquid. The aliphatic amide and/or the aromatic amide particularly an aliphatic amide and/or an aromatic amide being soluble in water and having a relatively low molecular weight remove effectively foulants adhered on an aromatic polyamide RO membrane.