Hybrid composites for contaminated fluid treatment

Abstract

Compositions, methods of making the compositions, systems, and processes for treating a fluid containing a contaminant are presented. The treatment reduces the concentration of contaminants, such as such as toxic metals, metalloids, oxyanions, and dissolved silica. The reduction in concentration of a contaminant may be sufficient so as to effect remediation of the fluid with respect to the contaminant. The treatment may reduce the concentration of a plurality of contaminants. The composition typically includes zero-valent iron, an iron oxide mineral, and ferrous iron. The ferrous iron promotes maintenance of the iron oxide mineral. The iron oxide mineral may, in turn, promote the activity of the zero-valent iron. The processes and systems may involve multiple stages. A stage may be optimized for treatment with respect to a particular contaminant. Examples of contaminated fluids include aqueous fluids, such as groundwater, subsurface water, and aqueous industrial waste streams. The compositions, systems, and processes are robust and flexible.

1 . A treatment system for removing or reducing the concentration of a contaminant comprised in a fluid, the treatment system comprising a first reactive zone, the first reactive zone comprising:
 (a) a first reactive solid comprising a base material defined as zero-valent iron or zero-valent zinc and a supplementary material comprising one or more iron oxide minerals in contact with the base material;   (b) a first secondary reagent, wherein the first secondary reagent is in contact with the reactive solid; and   (c) optionally a first additive,   wherein the first reactive zone is comprised in a first packed bed or a first fluidized bed.   
     
     
         2 . The treatment system of  claim 1 , wherein the first reactive zone is comprised in a first fluidized bed. 
     
     
         3 . The treatment system of  claim 2 , further comprising a first settling zone in fluid communication with the first reactive zone. 
     
     
         4 . The treatment system of  claim 1 , wherein the first reactive zone is comprised within a first reactor. 
     
     
         5 . The treatment system of  claim 4 , further comprising a sulfide generator in liquid communication with the first reactor. 
     
     
         6 . The treatment system of  claim 4 , further comprising at least a second reactor comprising a second reactive solid, a second secondary reagent, and optionally a second additive, wherein the second reactor is in fluid communication with the first reactor, such that the treatment system is further defined as a multi-stage reactor treatment system. 
     
     
         7 . The treatment system of  claim 1 , wherein the system further comprises one or more of the following: an internal solid/liquid separating zone, an aerating basin, a final settling basin, a wastewater pump, a reagent pump, or sand filtration bed. 
     
     
         8 . The treatment system of  claim 1 , wherein the first reactive solid comprises a plurality of particles. 
     
     
         9 . The treatment system of  claim 1 , wherein the first secondary reagent is further defined as a first ferrous iron. 
     
     
         10 . The treatment system of  claim 1 , wherein at least one iron oxide mineral of the supplementary material is magnetite. 
     
     
         11 . The treatment system of  claim 1 , wherein the first additive comprises a sulfide. 
     
     
         12 . The treatment system of  claim 1 , wherein the first additive comprises an oxidant. 
     
     
         13 . The treatment system of  claim 1 , wherein the contaminant comprises a metal, metal ion, metalloid, oxyanion, chlorinated organic compound, or a combination thereof. 
     
     
         14 . The treatment system of  claim 1 , wherein the contaminant is selected from arsenic, aluminum, antimony, beryllium, mercury, selenium, cobalt, lead, cadmium, chromium, silver, zinc, nickel, molybdenum, thallium, vanadium, and ions thereof; borates, nitrates, bromates, iodates, and periodates; trichloroethylene; and dissolved silica; and combinations thereof. 
     
     
         15 . The treatment system of  claim 1 , wherein the contaminant is selenate or dissolved silica. 
     
     
         16 . The treatment system of  claim 1 , wherein the fluid comprises industrial waste fluid. 
     
     
         17 . The treatment system of  claim 1 , wherein the pH of the reactive zone is between about pH 6 and about pH 8. 
     
     
         18 . A method of removing or reducing the concentration of a contaminant comprised in a fluid, comprising:
 (a) exposing the fluid to the first reactive solid comprised in the first reactive zone of the treatment system of  claim 1 ; and   (b) introducing the first secondary reagent of  claim 1  to the first reactive solid, thereby forming a composite that is active for removing or reducing the concentration of the contaminant.   
     
     
         19 . The method of  claim 18 , wherein the first secondary reagent is continuously introduced. 
     
     
         20 . The method of  claim 18 , further comprising a nitrate pretreatment step, wherein the composite is exposed a solution comprising nitrate prior to exposing the fluid to the composite.