Reverse Osmosis Membrane Sub-Osmotic Ion Separation
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Solution Overview
Problem
Conventional reverse osmosis (RO) processes struggle to effectively separate multivalent positive ions from solutions primarily composed of alkali cations and halide anions, as they require pressures exceeding osmotic pressure to function efficiently, which is not feasible for high ionic concentration solutions.
Innovation Solution
Operating a reverse osmosis membrane at sub-osmotic pressure to preferentially distribute multivalent cations into a reject solution, while allowing alkali cations and halide anions to pass through as a permeate, using a method that applies pressures below 0.9 times the osmotic pressure of the feed brine, thereby achieving a high salt rejection ratio and selective ion separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reverse osmosis processes apply pressure exceeding osmotic pressure to achieve efficient separation, then salt rejection ratio is improved, but the process becomes infeasible for high ionic concentration solutions due to excessive pressure requirements
Solution Approach 1:
The patent changes the pressure parameter from super-osmotic (conventional) to sub-osmotic (less than 0.9 times the osmotic pressure), fundamentally altering the operating conditions to achieve selective ion separation at feasible pressure levels while maintaining effective salt rejection
2Manufacturing precision
If conventional reverse osmosis processes are used to separate multivalent cations from alkali cations and halide anions, then separation is achieved, but the process cannot effectively preferentially separate multivalent cations from high concentration solutions
Solution Approach 1:
The patent changes the pressure parameter to sub-osmotic conditions, which fundamentally alters the separation mechanism to enable preferential distribution of multivalent cations to the reject stream even at high ionic concentrations (at least 4% by weight of alkali cations and halide anions)
Solution Approach 2:
Instead of using high pressure to force separation (conventional approach), the patent uses sub-osmotic pressure conditions that allow selective ion distribution to occur naturally, inverting the conventional pressure application approach to achieve better selectivity for multivalent cations
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 method allows for the efficient separation of multivalent cations from alkali cations and halide anions, achieving a high separation coefficient and improved ionic differentiation, even at high ionic concentrations, by operating the RO membrane at sub-osmotic pressures, facilitating the removal of ions like calcium and magnesium while maintaining a high recovery of permeate solution.
Implementation Method 1
a reverse osmosis (RO) membrane operating at a sub-osmotic pressure
Implementation Method 2
applying a sub-osmotic pressure to the feed brine... the sub-osmotic pressure being less than 0.9 times a measured osmotic pressure of the feed brine
Data Source
AI summary
A method of selectively separating ions, including: (a) providing a reverse osmosis (RO) separation arrangement having an RO membrane; (b) introducing a feed brine to the RO membrane, the brine containing multivalent cations, alkali cations and halide anions, a total concentration of the alkali cations and halide anions being at least 4%, by weight of the feed brine; (c) applying a sub-osmotic pressure to the feed brine, to drive a first portion of the brine through the RO membrane to produce a permeate solution, a remainder of the feed brine being rejected by the RO membrane and being discharged as a reject solution; the sub-osmotic pressure being applied so as to preferentially distribute the multivalent cations to the reject solution, with respect to the permeate solution; the sub-osmotic pressure being less than 0.9 times a measured or theoretical osmotic pressure of the feed brine.