Design of Sustainable Biomaterial Composite Adsorbents for Point-of-Use Removal of Lead Ions From Water

Abstract

The uncontrolled release of contaminants into aquatic environments has created the need for improved adsorbent materials for point-of-use (POU) treatment applications to address water security. The goal of this study was to prepare a low-cost sustainable adsorbent material with tailored Pb(II) adsorption properties in aqueous media. Several types of ternary composite adsorbents were prepared that contain chitosan, kaolinite, and a biomass additive (oat hulls or torrefied wheat straw), along with spectral characterization and thermal analysis of the adsorbents. The adsorption properties of the ternary composites with lead nitrate were studied at equilibrium using batch mode and dynamic conditions with a fixed bed column under variable experimental settings [flow rate, bed height, and Pb(II) concentration]. The adsorption capacity at equilibrium in synthetic or tap water was found to depend on the relative composition (wt.%) of additive components in the composite. The optimal composite adsorbent for maximum Pb(II) removal had the following composition (wt.%): chitosan (50%) + kaolinite (10%) + oat hulls (40%). Using this adsorbent, the dynamic adsorption properties with lead nitrate were studied in a fixed bed column at pH 6.5 and 295 K to reveal optimized Pb(II) removal that concur with the results obtained from batch studies. The sustainability of the biocomposite adsorbent was demonstrated with the use of relatively low-cost and locally available materials, whilst achieving favorable Pb(II) adsorption properties. The facile preparation of the optimal biocomposite adsorbent herein is proposed for use as a disposable POU filter media technology for the removal of lead and other multivalent heavy metal cations, including organic contaminants such as cationic dyes and agrochemicals.

Eggshell incorporated agro-waste adsorbent pellets for sustainable orthophosphate capture from aqueous media

“…This further highlights the synergistic adsorption properties among the components for this ternary composite system. 16,23…”

“…In turn, torrefaction of biomass affords improved properties such as handling, processing, and environmental stability. 11,17–23…”

Pyridinium-furfuryl-modified granular agro-waste adsorbent for orthophosphate recovery

“…IR band broadening occurs near 3500 cm −1 and 2880 cm −1 that signies potential H-bonding through OH-groups (and amine groups) within the structure between Oh and Chi, as well as kaolinite. 19,41 The characteristic N-H bend is observed at ca. 1663 cm −1 for all composites, while an additional sharp band at 1650 cm −1 appeared in the Oh50-Furfural system.…”

“…[14][15][16][17][18] The valorization of agro-waste as adsorbent materials by employing biomass such as oat hulls and wheat straw waste for the removal of lead ions and methylene blue highlight the utility of such materials. 19,20 The compositing of a chitosan with agro-waste can yield a high-value product with lower input chemical costs, and enhanced adsorption properties with greater access to the active sites, according to synergistic effects reported for such materials. 21,22 Biomass composites derived from spent coffee grounds or torreed wheat straw have favourable stability in aqueous media, especially under acidic conditions versus non-torreed biomass such as oat hulls.…”

“…Furthermore, these composites show susceptibility to breakdown in aqueous media with low salinity or slight acidity as outlined in previous research. 19,23 In turn, surface modication is required to reach acceptable mechanical strength and continued resilience in aqueous media for remediation applications in dynamic environments. For the case of aqueous media in many river systems, pH conditions reside near 7-8, where anion adsorption by chitosan can become attenuated or negligible.…”