Removal of arsenic from contaminated water using modified biopolymer-silica nanocomposite materials

Date

2014

Abstract

Filter materials were prepared from low-value agricultural by-products, i.e. rice hull nanosilica and chitosan, for the removal of inorganic arsenic from contaminated water. Rice hull nanosilica was obtained using two starting materials: (1) Light gray pulverized ash from whole rice hulls that were heated to ashing temperatures in the combustor, then subsequently subjected to sol-gel processing to obtain nanosilica powder with a size range of 20-80 nm by AFM analysis; (2) acid-washed ground rice hulls that were subjected to hydrothermal processing to obtain crude rice hull silica and sol-gel processing to obtain nanosilica with a size range of 5-10 nm, average BET surface area of 321 m2/g although this could reach approx 530 sq m/g, a pore radius of 17A deg and a silica content of 98-99% by EDX analysis. Because of the significantly shorter process for preparing nanosilica using the hydrothermal process, nanosilica produced from the acid-washed ground rice hulls using this process was adopted for all subsequent experiments and for the prototype fillers. The nanosilica thus obtained was modified using an iron salt in order to increase its affinity for arsenic. Two iron-modified nanosilica filter materials were produced: (a) iron-modified nanosilica powder which was prepared by mixing nanosilica, base and iron sulphate in an optimized ratio; and (b) iron-modified nanosilica aerogel beads which were prepared using the optimized ratio but at lower pH and in the presence of a non-solvent to facilitate bead formation. Commercial grade chitosan, from crab shells was modified with tyrosine and subsequently processed to obtain tyrosine-modified chitosan nanoparticles with an average size of 33 nm, a low surface area (4 sq m/g) by BET analysis and a pore radius of 17A deg. All of these materials were evaluated for their efficiency in arsenic remediation. In terms of overall cost, ease and consistency of preparation and removal efficiency, nanosilica aerogel beads modified with iron was found to be the best material for water filtration to remove arsenic. The iron-modified nanosilica beads is a novel material for removal of arsenic from contaminated water.

Language

English

Document Type

Article

Pages /Collation

76 leaves

En – AGROVOC descriptors

WATER; BIOLOGICAL CONTAMINATION; ARSENIC; RICE HUSKS; FILTRATION; BIOPOLYMERS; TYROSINE; SILICA

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