Multi-Stage Nanofiltration for Multivalent Ion Purity
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Solution Overview
Problem
Existing nanofiltration systems struggle to effectively increase the ratio of divalent or multivalent ions to monovalent ions in the retentate stream while minimizing monovalent ion concentration and reducing the risk of scale deposition, particularly in multistage treatment systems.
Innovation Solution
A method and system involving a multistage nanofiltration process where diluent water with lower total dissolved solids (TDS) concentration than the source water is introduced between stages to reduce monovalent ion concentration, using NF units with varying recovery rates and potentially recycling retentate streams, and employing different types of NF membranes to manage ion ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NF membranes are used to concentrate divalent and multivalent ions in the retentate stream, then the concentration of multivalent ions is increased, but the concentration of monovalent ions remains the same or increases, limiting the purity improvement
Solution Approach 1:
The patent divides the NF process into multiple stages with different recovery rates. The first NF unit operates at high recovery (60-80%) to concentrate multivalent ions, while subsequent NF units operate at lower recovery (20-60%) to progressively remove monovalent ions. This segmented approach allows independent optimization of each stage for different separation objectives, achieving both high multivalent ion concentration and high purity by addressing them in sequential steps rather than simultaneously.
2Quantity of substance
If the concentration of multivalent ions is increased in the NF retentate, then the ratio of multivalent to monovalent ions improves, but the risk of scale deposition increases
Solution Approach 1:
The patent applies preliminary action by introducing diluent water with lower TDS between NF stages, before the retentate enters subsequent concentration stages. This pre-dilution step reduces the ion concentration and scaling risk in the feed to downstream NF units, allowing the system to achieve higher overall multivalent ion concentration without exceeding saturation limits at any intermediate stage, thus preventing scale deposition.
Solution Approach 2:
The patent changes the TDS parameter of the feed stream by introducing diluent water between NF stages. This parameter change temporarily reduces ion concentration to below saturation levels, allowing the system to continue concentrating multivalent ions in subsequent stages without triggering scale deposition. The diluent water acts as a parameter adjustment mechanism to maintain operating conditions within safe limits.
3Manufacturing precision
If monovalent ion concentration is reduced in the NF retentate, then the purity of multivalent ion product increases, but the recovery rate of multivalent ions decreases
Solution Approach 1:
The patent segments the NF process into stages with different recovery rates optimized for different objectives. The first NF unit operates at high recovery (60-80%) to maximize multivalent ion concentration, while subsequent NF units operate at lower recovery (20-60%) to focus on monovalent ion removal. This segmentation allows the system to achieve both high recovery in the first stage and high purity in final stages, with the diluent water injections compensating for any multivalent ion losses.
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
This approach significantly increases the ratio of multivalent ions to monovalent ions in the retentate stream, reduces monovalent ion concentration, and minimizes the risk of scale deposition, achieving a high-purity mineral product.
Implementation Method 1
Nano-filtration (NF) is a well-known membrane-based pressure-driven separation method that is selective in rejecting different ions from a feed water source, depending, for example, on the size and charge of the ions and their salt diffusion coefficients in water
Implementation Method 2
between the nano-filtration stages diluent water having a total dissolved solids (TDS) concentration lower than a TDS concentration of the original saline source water is introduced into the preceding stage's NF retentate stream
Data Source
AI summary
A system and method to increase a ratio of multivalent ions to monovalent ions in a retentate of a multistage nanofiltration system from saline source water. Multiple nanofiltration units can be arranged in a series to selectively remove monovalent ions from the water fed into each nanofiltration stage in the nanofiltration permeate stream while retaining multivalent ions in the nanofiltration reject stream. The methods and systems may produce the concentrated multivalent ion product is suitable for many applications, which includes fertilizer for plants and remineralization of desalinated water.