Sorption of Coated and Uncoated Nanocrystalline Zinc Oxide from Aqueous Solutions onto Raw and Acetylated Cellulose Sago Hampas: Equilibrium, Kinetic and Thermodynamic Studies

In this study, sorption efficiency of coated (C-) and uncoated (U-) zinc oxide nanoparticles (ZnO-NPs) in aqueous solution onto raw sago hampas (RSH) and acetylated sago hampas (ACSH) was studied. Physical and chemical characteristics of both the sorbate and sorbents were analysed using various characterization techniques. The mechanism of the sorption process was evaluated using equilibrium isotherms, kinetic and thermodynamic studies. From the study, maximum percentage removal of both sorbate ions were achieved at an equilibration time of 100 minutes with an optimum sorbate mass of 2.0 g per 50 ml. The study recorded a maximum % removal of 85.1% & 87.6% for C-and U-ZnO-NPs (< 50 nm) onto RSH and 90.0% & 91.1% onto ACSH. Langmuir isotherm fitted well for the sorption process with the highest efficiency of 0.793 mg/g recorded for C-ZnO-NPs onto RSH. Pseudo-second model best described the sorption process. An exothermic and non-spontaneous sorption process was realised in all the sorption studies except that of U-ZnO-NPs (< 50 nm) onto ACSH which became spontaneous as temperature increased. Based on the findings from the multiple approaches employed, both sorbents could be proposed as viable alternatives to act as a green sorbent in the removal of ZnO-NPs from water and wastewater

Adsorption of Zinc Oxide Nanoparticles onto Esterified Carbonize Sago Hampas: Kinetic and Equilibrium Studies

Sago hampas was chemically modified through esterification process to adsorb both laboratory and commercial synthesized ZnO nanoparticles from water in a batch adsorption studies. The esterified sago hampas (ECSH) as a biosorbent w:as char:acterized using Energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) technique s. Investigating the effect of pH, contact time, initial sorbate ion concentration, temperature and sorbent mass were carried out where adsorption parameters were analyzed using Langmuir, Freundlich and Temkin models. The correlation between kinetics of adsorption and tgr rate order of ZnO nanoparticles on ECSH were also determined. The adsorption of the ZnO nanoparticles was found to increase with increasing contact time with the attainment of equilibrium at 100th minutes with maximum removal efficiency of 85.5% (0.036 mg/g) and 89.6% (0.106 mg/g) ZnO nanoparticles for laboratory and commercial synthesized ZnO from aqueous solution. An optimum pH of 8 with adsorbent dose of 2.0 g at a temperature of 50 oC gave good results of ZnO nanoparticles removal. The equilibrium data for both sorbate solution fitted well for both Langmuir and Freundlich isotherm models. From the Langmuir model, ECSH recorded greater sorption capacity of 0.2 mg/g and 0.6 mg/g for both laboratory and commercial synthesized ZnO nanoparticles respectively. The kinetic studies showed pseudo-second order model as the best fitted for the sorption of ZnO nanoparticles for both synthesized samples

Removal of zinc oxide nanoparticles in aqueous environment using functionalized sorbents derived from sago waste

The increase in sago processing industries especially in Malaysia has inadvertently created its waste efect on the environment. The study therefore modifed the raw sago waste residue (hampas) generated by three (3) chemical processes; esterifcation, acetylation and phosphorylation. The as-prepared sorbents were characterized by surface area analyser (BET), Fourier transform infrared (FTIR) spectroscopy, feld emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Thereafter, their sorption efciencies were evaluated on zinc oxide nanoparticles in lake water in a laboratory-scaled column-bed sorption study. Spectra analysis confrmed the presence of ester and ether functionality in the esterifed and acetylated samples, whereas phosphoric ester and amine functionality were present in the phosphorylated sample. The acetylated sample recorded the largest surface area (29.02 m2 /g) and degree of substitution (1.99). The experimental data established that acetylated sago residue recorded the maximum column capacity of 4.50 mg/g in all the parameters examined. Meanwhile, increase in infuent concentration (1.51–5.04 mg/L) and fow rate (4.20–6.60 ml/min) decreased the breakthrough time while increase in column-bed height (3–7 cm) increased the breakthrough time for the three sorbents. However, Adams–Bohart model adequately described the behaviour of the sorption process better than Thomas and Yoon–Nelson models. The results suggested that acetylated sago residue is potentially scalable for removing zinc oxide nanoparticles from water

Validation of the Atomic Absorption Spectroscopy (AAS) for Heavy Metal Analysis and Geochemical Exploration of Sediment Samples from the Sebangan River

This study was to validate the Atomic Absorption Spectroscopy (AAS) in the determination of heavy metals using surface sediments from the Sebangan (estuary of Sadong River), Sarawak State, Malaysia as a case study. Aqua regia procedure was used to extract the trace elements from the sediments. The Scanning Electron Microscope was used to analyse and investigate the microstructure morphology and chemical composition characterizations of the sediments. The results of the examination confirmed to the fact that the technique validated was appropriate and less laborious for the determination of the 12 metals of interest (Al, Mn, Ca, Cd, Cu, Fe, Cr, Ni, Co, Zn and Pb) in the sediment. Massive deposits of sharp teeth granite and quartz particles of distinct tetrahedral conformation with plus size were observed in the samples investigated

Zinc Oxide Nanoparticles Synthesis Methods and its Effect on Morphology: A Review

Zinc oxide is an important material with numerous applications due to its unique properties. Due to their thermal and chemical stability are used in wide applications such as LEDs, sensors, catalysts, and photodetectors. Different chemical, physical, and biological methods have been adopted to achieve the intended result, as enumerated in many pieces of literature. Therefore, selecting an efficient synthesis process is essential, which is a key factor that significantly influences the efficacy of the synthesized nanocrystalline materials. The chemical synthesis of nanoparticles (NPs) via hydrothermal, solvothermal, and sol-gel routes is considered effective as high-quality crystalline structures are produced. Control of parameters of processes yields excellent morphological features of the synthesized samples. This review explored the different parameters of processes and their effect on the morphology of ZnO nanostructures via hydrothermal, solvothermal, and sol-gel techniques. Finally, some ZnO nanocomposites molecules are reviewed as per the dopant used and its effect on the sample compound synthesized

Synthesis and Characterization of Single Phase ZnO Nanostructures Via Solvothermal Method : Influence of Alkaline Source

Single phase ZnO nanostructures were synthesized by a simple and low temperature solvothennal process from two different alkaline sources; Potassium hydroxide (KOH) and Sodium hydroxide (NaOH) with zinc acetate dihydrate (Zn(CH3COO)2·2H20) as precursor. This facile and rapid synthesis technique achieve high purity of Zinc oxide (ZnO) nanostructures in large scale negating the use of complex and high temperature routes. The synthesized particles were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transfonn Infrared (FT-IR) Spectroscopy, and Ultraviolet Visible (UV-Vis) spectroscopy. ZnO synthesized using KOH and NaOH exhibit wurtzite hexagonal and flake-like nanostructures with average crystallite size of 11.0 nm and 14.9 nm respectively. The optical absorption spectra of the two samples showed absorption bands of 367.70 and 365.30 nm. The results showed the effect of alkaline sources on the surface morphology, structural and optical properties of ZnO

Effects of Humic Acid and Natural Sunlight Irradiation on the Behaviour of Zinc Oxide Nanoparticles in the Aqueous Environment

The unique properties of ZnO nanoparticles have attracted scientists’ interest to produce on a large-scale. Household items, cosmetics, consumer products, and electric sensors are some products that utilize these ZnO nanomaterials. Eventually, ZnO nanoparticles will be released into the environment in various ways. Once released, ZnO nanoparticles would dissociate into Zn2+ ions, which are toxic to aquatic organisms. The presence of humic acid and exposure to sunlight could affect the dissolution of ZnO nanoparticles. Two sizes of commercial ZnO nanoparticles (< 50 nm and < 100 nm) were chosen to study the influence of humic acid and sunlight on the dissolution. In the presence of humic acid, the dissolution of both sizes is higher, with 67 % and 39 % Zn2+ dissolved for < 50 nm and < 100 nm, respectively. The concentration of Zn2+ ions seems to be consistent or stable when exposed to sunlight. However, the humic acid enhanced the release of Zn2+ ions. Langmuir isotherm model best fitted for the humic acid's sorption onto the ZnO nanoparticles with the process been favorable

Biosynthesis, characterization, and antibacterial activity of ZnO nanoaggregates using aqueous extract from Anacardium occidentale leaf: comparative study of different precursors

Background Various parts of Anacardium occidentale plant possess curative qualities like antidiabetic, anti-inflammatory, antibacterial, antifungal, and antioxidant. Aqueous extract of this plant leaf was used in biosynthesizing zinc oxide (ZnO) nanoaggregates using two precursors of zinc salt (zinc acetate dihydrate [Zn(CH3COO)2∙2H2O] and zinc chloride [ZnCl2]). The synthesized ZnO samples were used in a comparative study to investigate the antibacterial activity against selected Gram-positive and Gram-negative microbes [Staphylococcus aureus, Exiguobacterium aquaticum (Gram +ve) and Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii (Gram −ve)]. The synthesized ZnO nanoaggregates from the two precursors were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive x-ray spectroscopy (EDX) techniques. Results Micrographs of SEM and TEM confirmed nanoparticles agglomerated into aggregates. While spherical nanoaggregates were identified in samples prepared from Zn(CH3COO)2∙2H2O, flake-like structures were identified in samples synthesized from ZnCl2. Particle size determined by TEM was 107.03 ± 1.54 nm and 206.58 ± 1.86 nm for zinc acetate dihydrate and zinc chloride precursors respectively. ZnO nanoaggregate synthesized using zinc acetate as precursor gave higher antibacterial activity than its counterpart, zinc chloride with K. pneumonia recording the highest inhibition zone of 2.08 ± 0.03 mm (67.53%) whereas S. aureus recorded the least inhibition zone of 1.06 ± 0.14 mm (34.75%) for ZnO nanoaggregate from zinc chloride precursor. Also, antibacterial activity increases with increasing concentration of the extract in general. However, A. baumannii, E. aquaticum, and K. pneumoniae did not follow the continuity trend with regards to the 250 ppm and 500 ppm concentrations. Conclusion Biosynthesis of ZnO nanoaggregates using aqueous extract of A. occidentale leaf from zinc acetate dihydrate and zinc chloride as precursors was successful with the formation of nanospheres and nanoflakes. The study suggested that A. occidentale sp. could be an alternative source for the production of ZnO nanoparticles and are efficient antibacterial compounds against both Gram +ve and Gram −ve microbes with its promising effect against infectious bacteria

Synthesis, Characterization, and Antibacterial Activity of ZnO Nanoparticles from Organic Extract of Cola Nitida and Cola Acuminata Leaf

The study aimed at the synthesis and antibacterial activity of ZnO nanoparticles (NPs) from organic extracts of Cola nitida and Cola acuminata leaf using zinc chloride (ZnCl2) and zinc acetate dihydrate [Zn(CH3COO)2∙2H2O] as precursors on selected Gram positive and Gram negative microbes: Staphylococcus aureus, Exiguobacterium aquaticum, (Gram +ve) and Escherichia coli, Klebsielia pneumonia, Acinetobacter baumanni (Gram –ve). Spherical and flake-like nanostructures were recorded by Scanning Electron Microscopy (SEM) for C. acuminata and C. nitida respectively for the two precursors used. The average particle size and crystallite size determined by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) for C. acuminata and C. nitida were in the range of 32.15-43.26 nm; 69.12-84.26 nm and 14.69-17.12 nm; 23.68-23.96 nm respectively. Energy-dispersive X-ray spectroscopy (EDX), UV- visible spectroscopy (UV-vis), Atomic Absorption Spectroscopy (AAS) and Fourier-transform infrared spectroscopy (FT-IR) techniques were used to observe the purity and surface functional groups of the samples. Spectra peaks at 440-458 cm-1 and 364-370 nm confirmed the presence of ZnO in the samples by FT-IR and UV-vis, whereas AAS at 213.9 nm wavelength further confirmed elemental zinc with a percentage atomic weight of 71.37% as against 69.50%, 18.8% and 11.1% for Zinc, Oxygen and Carbon by EDX. Data from the antibacterial activity studies show an increase in inhibition rate as concentration of the ZnO NPs increases in concentration from 25-1000 ppm. ZnO NPs from the two extracts recorded the highest inhibition rate in Acinetobacter baumanni of approximately 88% and 49% using ZnCl2 and Zn(CH3COO)2∙2H2O respectively

Synthesis, Characterization, and Antibacterial Activity of ZnO Nanoparticlesfrom Organic Extract of Cola Nitida and Cola Acuminata Leaf

The study aimed at the synthesis and antibacterial activity of ZnO nanoparticles (NPs) from organic extracts of Cola nitida and Cola acuminata leaf using zinc chloride (ZnCl2) and zinc acetate dihydrate [Zn(CH3COO)2∙2H2O] as precursors on selected Gram positive and Gram negative microbes: Staphylococcus aureus, Exiguobacterium aquaticum, (Gram +ve) and Escherichia coli, Klebsielia pneumonia, Acinetobacter baumanni (Gram –ve). Spherical and flake-like nanostructures were recorded by Scanning Electron Microscopy (SEM) for C. acuminata and C. nitida respectively for the two precursors used. The average particle size and crystallite size determined by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) for C. acuminata and C. nitida were in the range of 32.15-43.26 nm; 69.12-84.26 nm and 14.69-17.12 nm; 23.68-23.96nm respectively. Energy-dispersive X-ray spectroscopy (EDX), UV-visible spectroscopy (UV-vis), Atomic Absorption Spectroscopy (AAS) and Fourier-transform infrared spectroscopy (FT-IR) techniques were used to observe the purity and surface functional groups of the samples. Spectra peaks at 440-458 cm-1and 364-370 nm confirmed the presence of ZnO in the samples by FT-IR and UV-vis, whereas AAS at 213.9 nm wavelength further confirmed elemental zinc with a percentage atomic weight of 71.37% as against 69.50%, 18.8% and 11.1% for Zinc, Oxygen and Carbon by EDX. Data from the antibacterial activity studies show an increase in inhibition rate as concentration of the ZnO NPs increases in concentration from 25-1000 ppm. ZnO NPs from the two extracts recorded the highest inhibition rate in Acinetobacter baumanni of approximately 88% and 49% using ZnCl2and Zn(CH3COO)2∙2H2O respectively