Abstract
Pharmaceuticals and personal care products (PPCPs) are utilised to enhance public health and improve the quality of life. However, PPCPs have been the cause of more environmental problems in recent years. The contamination of public waters has been a significant environmental concern in modern times. Various techniques have been employed for the rehabilitation of contaminated water. Still, adsorption has proven to be a very effective method for the removal of pollutants such as PPCPs in water treatment issues. In recent years, researchers have endeavoured to find economical sorbents for water treatment, and they have gained significant interest since they provide a comprehensive alternative to costly methods. Adsorbent materials such as hydrogels possess exceptional attributes that render them the optimal adsorbent materials for the elimination of water pollutants. The objective of this work was to synthesise an innovative, cost-effective bio-nanocomposite adsorbent for the removal of PPCPs such as triclosan, caffeine, and ibuprofen from water.
Firstly, manganese sulphide nanoparticles (MnS NPs) were synthesised using solid-state technique at various synthesis temperatures, characterised, and applied for the effective removal of triclosan in aqueous solutions. TEM images were used to measure the particle size of the synthesised MnS NPs using ImageJ software, and results were found to range between 16.4 nm and 3.91 nm. Selection of the best-performing nanoparticles was done at various pH levels of 4, 6, and 8. It was noticed that MnS NPs @ 300, 350, and 400 ℃ exhibited high adsorption capacities for triclosan at pH 8. Adsorption kinetic studies were carried out at distinct initial concentrations of triclosan (10, 30, and 50 mg/L) to vary contact times using MnS NPs @ 300 ℃. Results showed when the experimental data had an initial concentration of 10 mg/L, the study favoured the intra-particle diffusion model. In contrast, when the initial concentration of triclosan was 30 and 50 mg/L, the experiment data best fit the pseudo-first-order for both concentrations.
Secondly, for the synthesis of the bio-nanocomposite hydrogel beads, sodium alginate (NaAlg) hydrogel beads were incorporated with distinct amounts of MnS NPs @ 300 ℃ to form new innovative materials for the effective removal of PPCPs in aqueous solutions. The novel NaAlg/MnSx bio-nanocomposite hydrogel beads were characterised using several techniques such as SEM, EDX, TEM, FTIR, TGA, and zeta sizer. Optimal conditions for the effective removal of triclosan in aqueous solutions were determined and found to be a pH of 8.68, an MA of 11.5 mg, and an SV of 35.1 mL. NaAlg/MnS0.05g bio-nanocomposite hydrogel beads were employed for the removal of triclosan, and adsorption studies were
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conducted. The material (NaAlg/MnS0.05g bio-nanocomposite hydrogel beads) was compared to various adsorbents used for the elimination of triclosan. The maximum adsorption capacity was 132 mg/g from the Langmuir model, which was comparable to the literature.
The rehabilitation of contaminated waters by caffeine in this work was carried out by using NaAlg/MnS0.05g bio-nanocomposite hydrogel beads. Optimal conditions were determined using a central composite design (CCD) for parameters such as pH, MA, and SV, and the values were 5.32, 10 mg, and 35.1 mL, respectively. Adsorption studies for the research work were carried out for isotherms, kinetics, and thermodynamics. The experimental adsorption capacity was 109 mg/g, and the experimental data for adsorption isotherms favoured the Sips model. Application to real water samples for NaAlg/MnS0.05g bio-nanocomposite hydrogel beads onto caffeine achieved a removal efficiency greater than 90%.
Ibuprofen, a non-steroidal anti-inflammatory drug (NSAID) that is frequently prescribed and is a member of PPCPs, has been identified as a significant pollutant in numerous water sources worldwide. In this study, NaAlg/MnS0.1g and NaAlg/MnS0.2g bio-nanocomposite hydrogel beads were utilised for the elimination of ibuprofen in aqueous solutions. Optimal conditions for the study were determined for pH, MA, and SV, and the numerical results were 7, 11.5 mg, and 35.1 mL, respectively. Adsorption studies were carried out on both adsorbents and ibuprofen removal in aqueous solutions. Adsorption kinetic and isotherm studies of NaAlg/MnS0.1g hydrogel beads onto ibuprofen were more accurately described by pseudo-second order and Sips models, respectively. In contrast, adsorption isotherm and kinetic studies for NaAlg/MnS0.2g hydrogel beads onto ibuprofen adsorption favoured Sips, Langmuir, and pseudo-second-order models. The maximum adsorption capacities of NaAlg/MnS0.1g and NaAlg/MnS0.2g adsorbents were 82.8 and 100 mg/g, respectively. Application onto real water samples achieved a removal efficiency of > 90%.
The intrinsic benefits of sodium alginate affordability, biodegradability, and functionalisation potential render it an optimal matrix for incorporating manganese sulphide nanoparticles, potentially improving adsorption kinetics and selectivity for PPCPs. To enhance performance, the synthesis process must focus on cross-linking techniques that achieve an optimal balance between mechanical stability and porosity. Future investigations should concentrate on customising pore structures to enhance surface area and adsorption capacity, while also ensuring environmentally sustainable regeneration cycles to reduce secondary waste. Thorough examination across diverse pH levels, temperature ranges, and
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competing ion scenarios akin to investigations involving heavy metals and antibiotics will elucidate practical application.