Seawater Boron Removal via pH Adjustment and Antiscaling Agents
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Solution Overview
Problem
Current boron removal processes from seawater using reverse osmosis membranes are costly, require multiple steps, and struggle to achieve the new 0.5 mg/l boron concentration limit due to high boron permeation as boric acid through polyamide membranes.
Innovation Solution
A single-step reverse osmosis process involving the addition of a metal-based antiscaling-dispersant agent, pH adjustment to 8-9.5, and optional fluoride or high molecular weight alcohol addition to convert boric acid into rejectable borate ions, preventing precipitation and enhancing boron rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-step reverse osmosis process is used with high rejection polyamide membranes followed by brackish water membranes, then boron removal efficiency is improved, but investment cost and operational complexity increase significantly
Solution Approach 1:
The patent applies preliminary action by adjusting the pH of feed water to alkaline conditions (pH 9.5-10) before the reverse osmosis process. This pre-treatment converts boric acid into borate ions, which are then effectively rejected by the membrane, achieving high boron removal in a single step without requiring complex multi-stage systems
Solution Approach 2:
The patent changes the pH parameter of the feed water from neutral to alkaline (pH 9.5-10) to transform the chemical form of boron from boric acid to borate ions. This parameter change enables effective boron rejection by reverse osmosis membranes while simplifying the overall process configuration to a single step
2Manufacturing precision
If pH is increased to 9.5-10 using caustic soda, then boron removal is improved, but reagent costs and operational expenses increase
Solution Approach 1:
The patent replaces expensive caustic soda with a cheaper alternative - a scale inhibitor containing phosphonic acid groups. This substance achieves the necessary pH adjustment and boron removal at lower cost, functioning as a disposable chemical additive that accomplishes the treatment objective without the high operational expenses of traditional caustic soda
3Productivity
If work conversion in the second step is increased to 90%, then water recovery is improved, but salt precipitation risk increases requiring large quantities of antiscaling agents
Solution Approach 1:
The patent extracts and removes scale-forming substances from the feed water through the reverse osmosis process itself, achieving high water recovery (90%) without generating harmful salt precipitation. The membrane process separates concentrate from permeate, allowing high recovery while preventing scaling by removing the substances that would otherwise precipitate
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
Achieves boron concentrations below 0.5 mg/l with reduced costs and operational complexity, maintaining efficiency even with reduced membrane salt rejection and partial blocking, while allowing for antiscaling agent monitoring via redox potential.
Implementation Method 1
procedure for elimination of boron from sea-water by reverse osmosis membranes
Implementation Method 2
addition of a metal-based antiscaling-dispersant agent
Data Source
AI summary
The present invention relates to a procedure for elimination of boron from sea-water by reverse osmosis membranes characterized in that it comprises:adding to sea-water a composition consisting of at least one metal together with at least one antiscaling-dispersant agent, anda second phase in which an alkalinizing agent is added until a pH of between 8-9.5 is achieved, which can furthermore consist of a third phase in which the fluoride content of the sea-water is increased following the second phase, or a third phase in which a high molecular weight alcohol is added to the water.