Patent ID: 9073763
Filing Date: 2015-07-07
Classification: B01D,C01B,C02F

Abstract:
1. In a process for the purification of an aqueous solution comprising solutes and solvent, said solutes comprising at least some hardness, at least some alkalinity, and at least some total organic carbon (TOC), by using membrane separation equipment to increase the concentration of said solution to a preselected concentration factor, said membrane separation equipment consisting essentially of the type which has a semi-permeable membrane therein that substantially resists the passage of dissolved species therethrough, by passing a portion of said aqueous solution through said semi-permeable membrane in a first unit of said membrane separation equipment to produce a product stream, and retaining at least a portion of said aqueous solution in said first unit of said membrane separation equipment to increase the concentration of a preselected solute to a preselected concentration factor in said retained portion of said aqueous solution, the improvement which comprises controlling solutes, hardness, alkalinity, and carbon dioxide in said aqueous solution to a level where the tendency to form scale is effectively eliminated at said preselected concentration factor, by (a) prior to feed of said aqueous solution to said first unit of said membrane separation equipment having said semi-permeable membrane therein, optimally, in any order, (i) minimizing hardness of said aqueous feed solution; (ii) minimizing alkalinity of said aqueous feed solution, and (iii) minimizing carbon dioxide dissolved or suspended therein, and (b) then, after step (a), increasing the pH of said aqueous feed solution to at least 8.5, and (c) wherein said TOC is rejected by said semi-permeable membrane by at least 95%.