Selective capture of hexavalent chromium from an anion-exchange column of metal organic resin–alginic acid composite

Abstract

We report an anion exchange composite material based on a protonated amine-functionalized metal-organic framework, denoted Metal Organic Resin-1 (<b>MOR-1</b>), and alginic acid (<b>HA</b>). <b>MOR-1-HA</b> material shows an exceptional capability to rapidly and selectively sorb Cr(vi) under a variety of conditions and in the presence of several competitive ions. The selectivity of <b>MOR-1-HA</b> for Cr(vi) is shown to be the result of strong O₃Cr^VI···NH₂ interactions. The composite sorbent can be successfully utilized in an ion-exchange column, in contrast to pristine <b>MOR-1</b> which forms fine suspensions in water passing through the column. Remarkably, an ion exchange column with only 1% wt <b>MOR-1-HA</b> and 99% wt sand (an inert and inexpensive material) is capable of reducing moderate and trace Cr(vi) concentrations to well below the acceptable safety limits for water. The relatively low cost of <b>MOR-1-HA</b>/sand column and its high regeneration capability and reusability make it particularly attractive for application in the remediation of Cr(vi)-bearing industrial waste.