Optimization of reaction parameters in hydrothermal synthesis: a strategy towards the formation of CuS hexagonal plates

BACKGROUND: For decades, copper sulphide has been renowned as the superior optical and semiconductor materials. Its potential applications can be ranged from solar cells, lithium-ion batteries, sensors, and catalyst systems. The synthesis methodologies of copper sulphide with different controlled morphology have been widely explored in the literature. Nevertheless, the understanding on the formation chemistry of CuS is still limited. The ultimate approach undertaking in this article is to investigate the formation of CuS hexagonal plates via the optimization of reaction parameters in hydrothermal reaction between copper (II) nitrate and sodium thiosulphate without appending any assistant agent. RESULTS: Covellite (CuS) hexagonal plates were formed at copper ion: thiosulphate ion ([Formula: see text]) mole ratio of 1:2 under hydrothermal treatment of 155°C for 12 hours. For synthesis conducted at reaction temperature lower than 155°C, copper sulphate (CuSO(4)), krohnite (NaCu(2)(SO(4))(H(2)O)(2)] and cyclooctasulphur (S(8)) were present as main impurities with covellite (CuS). When [Formula: see text] mole ratio was varied to 1: 1 and 1: 1.5, phase pure plate-like natrochalcite [NaCu(2)(SO(4))(H(2)O)] and digenite (Cu(9)S(5)) were produced respectively. Meanwhile, mixed phases of covellite (CuS) and cyclooctasulphur (S(8)) were both identified when [Formula: see text] mole ratio was varied to 1: 2.5, 1: 3 and 1: 5 as well as when reaction time was shortened to 1 hour. CONCLUSIONS: CuS hexagonal plates with a mean edge length of 1 μm, thickness of 100 nm and average crystallite size of approximately (45 ± 2) nm (Scherrer estimation) were successfully synthesized via assisting agent- free hydrothermal method. Under a suitable [Formula: see text] mole ratio, we evidenced that the formation of covellite (CuS) is feasible regardless of the reaction temperature applied. However, a series of impurities were attested with CuS if reaction temperature was not elevated high enough for the additional crystallite phase decomposition. It was also identified that [Formula: see text] mole ratio plays a vital role in controlling the amount of cyclooctasulphur (S(8)) in the final powder obtained. Finally, reaction time was recognized as an important parameter in impurity decomposition as well as increasing the crystallite size and crystallinity of the CuS hexagonal plates formed

Multithiol functionalized graphene bio-sponge via photoinitiated thiol-ene click chemistry for efficient heavy metal ions adsorption

Heavy metals contamination in the natural waters remains an unresolved environmental challenge pressing for the development of purification technologies. This paper presents the green engineering of a new bio-sponge for heavy metals adsorption composed of alginate bio-polymeric network encapsulated with reduced graphene oxide (rGO) modified with iron oxide nanoparticles and covalently attached multithiol (pentaerythritol tetrakis-mercaptopropionate) molecules using photoinitiated thiol-ene click chemistry. The multithiol functionalized graphene bio-sponge (SH-Graphene bio-sponge) is designed to enhance adsorption performances of heavy metals including structural approach combined with oxygen functionalities and high density of sulfur-containing groups (10.2 at % S, confirmed by X-ray Photoelectron Spectroscopy, XPS) with high binding affinity towards specific heavy metals (Cd and Pb). It was shown that the level of thiol functionalization on the graphene structure within the bio-sponge can be controlled by tuning the Ultraviolet (UV) irradiation time without adjusting the concentration of the precursors. SH-functionalized graphene bio-sponge showed outstanding adsorption capacity for Pb (II): 101.01 mg/g and Cd (II): 102.99 mg/g, outperformed commercial and literature reported adsorbents in highly competitive selectivity studies using co-existing heavy metal ions (Cu, Co, Pb and Cd) spiked- sea water. The multithiol modified bio-sponge also showcased an excellent stability and reusability feature with only 0.015 mg/L Pb (II) detected, conforming the strict United States Environmental Protection Agency (US EPA) maximum contaminant level (MCL) for lead, after five recurring cycles using mixed heavy metal ions solution and acidic eluent. The outcomes from this work present valuable and promising contribution towards the development of a scalable and sustainable adsorbents for efficient remediation of heavy metals from waters.Pei Lay Yap, Yow Loo Auyoong, Kamrul Hassan, Farzaneh Farivara, Diana N.H.Tran, Jun Ma, Dusan Losi

All-in-one bioinspired multifunctional graphene biopolymer foam for simultaneous removal of multiple water pollutants

First published: 09 August 2020Polluted waters are complex systems with many different co‐existing contaminants that make their simultaneous removal a very challenging task. To address this problem, all‐in‐one ad/ab‐sorbent with unique combination of interfacial properties and multiple surface chemistry is developed to simultaneously and efficiently remove several pollutants including heavy metals, dyes, oils, and organic solvents. By mimicking the wetting micro‐topology of a darkling beetle with a combined hydrophilic‐hydrophobic surface, a new bioinspired adsorbent, graphene biopolymer foam (Alg‐Fe3O4‐rGO‐4S) for removal of multiple water pollutants is engineered by combining alginate (Alg) and reduced graphene oxide (rGO) functionalized with tetrathiol that is also decorated with iron oxide nanoparticles (Fe3O4). This concept is first proved by single pollutant removal, showing adsorption capacity of 789.7 ± 36 mg/g for methylene blue (MB), 107.0 ± 2.1 mg/g for Hg (II), 73.5 ± 0.7 mg/g for Cu (II), and rapid oil‐water separation with high sorption capacity (11–18 g/g). A remarkable performance for simultaneous removal of their mixtures in milli‐Q, river, and sea water is demonstrated with efficiency for MB (≈90%), Cu (II) (>99.99%) and Hg (II) (100%) and rapid (≈30 s) uptake of organic solvents and oils. The obtained results indicate a valuable potential of proposed concept for simultaneous removal of co‐existing water pollutants.Pei Lay Yap, Kamrul Hassan, Yow Loo Auyoong, Negar Mansouri, Farzaneh Farivar, Diana N. H. Tran and Dusan Losi