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.
Highlights
The widespread occurrence of heavy metals in the environment has led to increasing concerns of such contaminants on human and ecosystem health
The greater adsorption capacity for CPKO40 listed in Table 2 (Qm = 1,910 μg/g) provided the basis for selection of this Chitosan pellets (CP) material for the fixed-bed column study
This study reports on the preparation and characterization of several binary and ternary composite pellet materials that contain chitosan (CP), kaolinite and agro-waste biomass at variable composition
Summary
The widespread occurrence of heavy metals in the environment has led to increasing concerns of such contaminants on human and ecosystem health. The improper use of corrosion inhibitors and water quality conditions in the distribution system led to exceedingly high levels of lead (13,200 ppb) leaching into the drinking water supply for the city of Flint, where such values were ca. The elevated lead levels during the Flint crisis led to serious concerns for human health due to its neurotoxicity, behavioral and cognitive development effects, where ca. The widespread occurrence of lead contamination was outlined due to leaching from the distribution systems in various Canadian cities (Cribb et al, 2019). In 2019, elevated lead levels were reported in two Saskatchewan cities, where the average value (22 ppb) was above the prescribed maximum guideline (5 ppb) set forth by Health Canada (Wilson and Ackerman, 2019).
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