| In environmental separation and remediation, many nanoscale inorganic particles (NIPs) offer favorable properties for selective separation and/or chemical transformation of target contaminants. For example, (i) hydrated Fe(III) oxide (HFO) particles can selectively sorb dissolved heavy metals or metalloids; (ii) Mn(IV) oxides are strong oxidizing agents; (iii) magnetite crystals are capable of imparting magnetic activity. The preparation of NIPs is safe, simple, and inexpensive. However, these tiny particles cannot be used in fixed-bed columns or in any plug flow type configuration due to excessive pressure drops and poor durability. Harnessing these NIPs within polymeric beads offers new opportunities in the area environmental separation and control.; This study reports the preparation and environmental applications of two classes of polymer-supported HFO nanoparticles: (i) magnetically active dual-zone sorbent (DZS) and (ii) arsenic-selective hybrid ion exchanger (HAIX). The main components of these hybrid polymeric sorbents include: (i) a durable polymer resin and (ii) HFO or magnetite nanoparticles dispersed within the polymer beads.; Laboratory experiments demonstrated that DZS, in addition to being magnetically active, is capable of selectively removing Cu(II), As(V), As(III), and DCP. DZS also showed favorable regeneration efficiency using a two step procedure. With less than 10 bed volumes of regenerant over 90% of sorbed species were recovered.; Sorption tests proved that arsenic-selective HAIX particles were selective for both As(III) and As(V). The preference of arsenic over sulfate or chloride is due to the formation of stable inner-sphere complexes. In contrast, phosphates competed with arsenic as demonstrated by separation factors As/P of 1.4 to 4.5. HIX particles were also amenable to efficient regeneration. Less than 10 bed volumes of regenerant consisting of 3%NaCl and 2%NaOH were adequate to recover over 90% of sorbed compounds. HAIX also ran well with groundwaters containing 45--150 mug/L of arsenic, over 10,000 bed volumes of groundwater were treated before any significant arsenic breakthrough. Kd values above 20,000 demonstrate the high affinity of HAIX for arsenic.; Kinetic studies confirmed that intraparticle diffusion was the primary rate-limiting step for As(V) sorption. HAIX exhibited faster kinetics for As(V) removal due to the influence of physical morphology and chemical functional groups. |
