- Title
- Tailoring biosorbents for remediation of selective organic and inorganic contaminants: Sorption mechanism and interfacial interaction
- Creator
- Hassan, Masud
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Remediation of heavy metals and emerging contaminants is essential due to their potential toxicity, mobility, transferability in the soil and water system. The adsorption technology showed extensive application due to its effectiveness in removing organic and inorganic contaminants from water, which is recognized as a cost-effective method and is more efficient than other contemporary techniques. Over the last few decades, many adsorbents including activated carbon, biochar, clay, graphene, nanomaterials, and composites materials, have been speculated as able to remediate organic and inorganic contaminants. However, most traditional and commercial adsorbents are not task-specific because they are not able to select the targeted contaminants. The properties of sorbent materials are crucial for their sorption performance. Surface area, porosity, active sites, specific electronics, and spatial characteristics of adsorbents can be tailored for binding target adsorbates from an aqueous solution. The surface assimilation method offers flexibility in style and operation, which can achieve high-quality treated effluent. This project focuses on the removal of typical heavy metals and emerging organic contaminants onto tailored biosorbents. Thus, various selective biosorbents were prepared for the removal of selected organic and inorganic pollutants (heavy metals, dyes, and PFAS). Heavy metals (Cd, Cu, Ni, Pb) as ionic inorganic pollutants, dyes (Methylene blue (MB)) as non-persistent organic dyes, and PFAS (PFOS) as persistent organic contaminants have been investigated for adsorptive removal using the tailored materials prepared in this project. Biochar and biopolymer as biosorbents have been employed for functionalization to enhance the adsorption of targeted organic and inorganic contaminants. Biochars have multifunctional properties that make them promising adsorbents for the remediation of organic and inorganic contaminants from soil and water system. Magnetic modification of biosorbent is also designed for easy and effective separation of the biosorbent after sorption process. Metal-based functional groups of magnetic biosorbent can contribute to an ion-exchange reaction, which affects the adsorption capacity of ionic contaminants and catalytic degradation of non-persistent organic pollutants. Hydrophobic metal oxides modified biosorbent (RMSDN600 and SD600) were prepared and used for the removal of PFOS from aqueous solutions. Results revealed the adsorption of PFOS was governed by both hydrophobic and electrostatic interaction, with hydrophobic interaction being the dominant sorption mechanism. The adsorption of PFOS declined as the pH solution increased due to rising electrostatic repulsion among negatively charged functional groups and anionic PFOS tails. Further investigation was conducted for the removal of heavy metals ions by functionalized mesoporous biopolymer. Mesoporous-biopolymer-architecture (HNT-BC@Alg) was synthesized for the adsorption of heavy metals. Initially, halloysite nanotubes (HNT) and ball-milled biochar (BC) were incorporated into biocompatible mesoporous adsorbents (HNT-BC@Alg), which were synthesized for adsorption of heavy metals. HNT-BC@Alg outperformed the BC, HNT, and BC@Alg in removing cadmium (Cd), copper (Cu), nickel (Ni), and lead (Pb). Mesoporous structure (∼7.19 to 7.56 nm) of HNT-BC@Alg was developed containing an abundance of functional groups induced from encapsulated BC and tubular HNT, which enabled heavy metals to infiltrate and interact with the adsorbents. Siloxane groups from HNT, oxygen-containing functional groups from BC, and hydroxyl and carboxyl groups from alginate polymer play a significant role in the adsorption of heavy metal ions. The reduction of surface area, porosity, and pore volume of expended adsorbents and sorption study confirmed pore filling and intraparticle diffusion played a considerable role in removing heavy metals. This project also investigates the removal of non-persistent dyes (methylene blue) found on mesoporous biopolymer beads from wastewater. Alginate biopolymers were used to stabilize halloysite nanotubes (HNTs) and zinc-nickel ferrite nanoparticles (NiZnFe4O4 < 100 nm). NiZnFe4O4 was used in and around the polymer beads to generate the porous polymer framework's magnetic properties and catalytic degradation. The adsorbents (NiZnFe4O4-HNT@alg) have a suitable surface area (122.43 m2/g), average pore diameter (~ 6.68 nm), pore volume (0.11 cm3/g), and abundance of active sites, enabling high adsorption capacity (264 mg/g) of methylene blue. The removal efficiency of MB was ~ 99% under a wide solution pH range from 10 mg/L of MB, in which the adsorbent dose was 2 g/L. This project investigates the removal of PFOS as persistent organic, methylene blue as non-persistent organic, and heavy metals as inorganic contaminants. The removal percentages of all selected contaminants are large enough to show that remediation is not only possible at higher concentrations but also at environmentally relevant concentrations of the adsorbates. All the adsorbents’ materials used in this project were tailored to enhance the sorption performance for the targeted contaminants from aqueous solution. However, complete removal of some of the organic and inorganic contaminants remains challenging, and this issue needs to be addressed in future research.
- Subject
- biochar; adsorption; contaminants; heavy metals; biopolymer; halloysite nanoclay; removal; PFAS; functionalization of adsorbent
- Identifier
- http://hdl.handle.net/1959.13/1508693
- Identifier
- uon:56145
- Rights
- Copyright 2022 Masud Hassan
- Language
- eng
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