Process for the treatment of a colloidal suspension

#This invention relates to a novel process for solid-liquid separation of contaminants, colorants and other solid suspended matter from a colloidal-suspension to yield a clarified effluent and an apparatus therefor.

#According to conventional methods for the separation of solids suspended in a suspension, an inorganic metal salt flocculating agent, for instance, aluminum sulfate or ferric chloride is added to the suspension so as to flocculate colloidal particles, of the suspended matter, promote coagulation of the flocced particles and increase the precipitation rate thereof so as to facilitate separation of the solids from the suspension.

#When the precipitation rate of the solids is to be increased, conventionally an organic high molecular weight flocculating agent is incorporated in the suspension to increase the coagulum of flock and thus accelerate the precipitation rate thereof.

#For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

#FIG. 1 is a schematic drawing which depicts one embodiment within the scope of the instant invention; and

#FIG. 2 is a schematic drawing which depicts another embodiment within the scope of the invention.

#The water clarification and purification and solids-separation process comprises adding a small, but effective amount of an inorganic metal salt flocculating agent to a colloidal suspension having a solids concentration which is less than 10 g/l, the amount of inorganic metal salt flocculating agent added to the suspension being sufficient to destabilize the colloidal suspension to initiate coagulation of the colloidally-suspended solids into small particles termed microflock. Before metal ions of the salt substantially completely hydrate to the corresponding hydroxides, at least 0.5 ppm of an organic high molecular weight flocculating agent is added to the suspension to convert the microfloc into strongly bonded large particles. The treated suspension is subjected to agitation, and preferably to agitation of the type which imparts simultaneously an upward and rotational flow to the mass of suspended particles for thereby effecting intimate particle-liquid contact, whereby the particles granulate. The granulates formed thereby are collected. The liquid phase of the suspension is separated as a supernatant from the solids as the suspension moves upwardly; the solids suspended therein are extracted as granules which can be condensed into a cake, and a purified supernatant may also be collected.

#In the specification and claims that follow, the expression "inorganic metal salt flocculating agent" is defined as a reagent that promotes instability in a colloidal suspension, and for convenience will be termed "IFA." Suitable inorganic metal salt flocculating agents within the scope of the definition and which may be employed in the instant process include aluminum sulfate, polyaluminum chloride, ferric sulfate, ferric chloride, ferrous sulfate and magnesium carbonate.

#Likewise, in the specification and claims that follow, the expression "organic high molecular weight flocculating agent" for convenience, shortened to "OFA," is defined to include the class of reagents which promotes strong bonding between suspended particles by the reaction thereof with the defined IFA class under specific process conditions. Suitable OFA within the scope of the definition which may be employed in the instant invention include polyacrylamide, a partially hydrolyzed compound of said polyacrylamide, sodium polyacrylate and like agents known to those skilled in the art.