Abstract
Over the past decades, organic-inorganic hybrid polymers have been applied in different fields, including the adsorption of pollutants from wastewater and solid-state separations. In this review, firstly, these compounds are classified. These compounds are prepared by sol-gel method, self-assembly process (mesopores), assembling of nanobuilding blocks (e.g., layered or core-shell compounds) and as interpenetrating networks and hierarchically structures. Lastly, the adsorption characteristics of heavy metals of these materials, including different kinds of functional groups, selectivity of them for heavy metals, effect of pH and synthesis conditions on adsorption capacity, are studied.
Highlights
A wide variety of toxic inorganic and organic chemicals are discharged into the environment as industrial wastes, causing serious water, air, and soil pollution
Some examples of nanocomposites are polyaniline-montmorillonite [112], polyaniline–V2O5 [113], polyvinyl alcohol-layered double hydroxide (LDH) [114], poly-N-vinyl carbazole-graphene oxide [115], etc. These compounds are incorporated in organic polymers as (a) a phase-separated structure in which the polymer can not intercalate within the inorganic layers and the inorganic component is dispersed as aggregates or particles within the polymer matrix; (b) an intercalated structure in which one or more polymer chains are inserted into the galleries of inorganic components and subsequently increase the interlayer spacing and (c) an exfoliated structure in which the insertion of polymer chains between inorganic sheets delaminates the layered compound [116] (Figure 5)
With the increase in alkalinity of solution, heavy metal ions convert to metal hydroxides and this decreases their affinity for interaction with binding sites of adsorbents [224] and in highly acidic solutions, H+ ions compete with metal ions for adsorption on the adsorbent surface [212]; (13) increasing the content of functional groups increases the adsorption capacity of these kinds of hybrid polymers it decreases their pore size and surface area [153,169,170]; and (14) adsorption capacities of hierarchically structure compounds are much greater than the other kinds of discussed organic-inorganic hybrid polymers and in the future they can be used as superadsorbents for the adsorption of heavy metals
Summary
A wide variety of toxic inorganic and organic chemicals are discharged into the environment as industrial wastes, causing serious water, air, and soil pollution. The recovery of heavy or valuable metals from water or wastewaters can often result in considerable cost savings and have both ecological and economic benefits Different methods, such as precipitation [6], solvent extraction [7] chemical and electrochemical techniques [8], ion-exchange methods [9] ultrafiltration [10] and reverse osmosis [11,12], flotation [13] and coagulation [14] have been developed for the removal of toxic metal ions from industrial effluents and wastewaters. This review describes classifications and synthesis methods of organic-inorganic hybrid polymers and particular attention will be focused on application of them for the adsorption of heavy metals from water as well as their performances and mechanisms
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