Effect of Oxidizers on Sulphide Removal from Hair Dissolving Liming Wastewater in Tannery

Liming and unhairing is the conventional operation in the tannery where raw animal skins are treated with sodium sulphide and calcium hydroxide to remove keratin proteins e.g., hair and wool epidermis and to dissolve nonstructural proteins. The hair dissolving liming process discharges wastewater containing soluble sulphide. In acidification, the sulphide in wastewater generates toxic hydrogen sulphide, which has a negative impact on the environment. In this present study, the efficiency of hydrogen peroxide (H2O2) and sodium chlorite (NaClO2) oxidizers are compared to remove sulphide from the hair dissolving liming wastewater. The soluble sulphide in the raw liming wastewater was 3666 mg/L. At optimized dose and pH for H2O2 and NaClO2 soluble sulphide in the solution were 109.2 and 54.6 mg/L, respectively. The sulphide removal efficiency for H2O2and NaClO2 were 97.0% and 98.5%, respectively at an optimum pH (pH 7). Before and after treatment the physicochemical parameters of the liming wastewater were analysed by observing different water quality parameters viz: pH, TDS, EC and salinity. At optimized condition TDS and salinity removal efficiency was 47.2%, 52.3% and 8.1%, 11.2% for H2O2 and NaClO2, respectively. This simple and easy method would be effective for treating hair dissolving liming wastewater in reducing soluble sulphide discharge from the tanneries. Journal of Engineering Science 12(3), 2021, 67-72

Obtaining Nickel Concentrates from Sludge Produced in the Process of Electrochemical Metal Surface Treatment

The article presents the possibility of recovering nickel from waste produced as a result of wastewater neutralization during the electrochemical surface treatment of metals. Leaching the sludge with concentrated hydrochloric acid enabled the metals contained in the sludge from precipitate to the solution with the efficiency of 74.4% (Se) to 100% (Zn). The content of elements was determined using the ICP-OES method. The next step was the precipitation of metals from the obtained solution using various reagents. The precipitating reagents used were 0.5 M sodium hydroxide solution, 0.5 M sodium sulphide solution and 1% dimethylglyoxime solution. Selective precipitation made it possible to obtain nickel concentrates with the content of nickel ranging from 15.3 to 98.2% for the first two methods, whereas in the case of the third method based on a dimethylglyoxime solution, the obtained nickel concentrate purity was 94.3%. The process of leaching nickel-dimethylglyoxime complex (Ni-DMG) with sulphuric acid and crystallization enabled obtaining 99.4% purity nickel sulphate, which can be reused in the nickel plating of selected metals. The research shows that waste generated in the process of neutralization of wastewater from electroplating plants is a potentially important source of recycled nickel concentrates.

Synthesis Luminescent Plasmonic Silver Nanoparticles and The Chemical Affinity towards sulphur atom in Sulphide and Thiourea molecules: Ab-Initio DFT Study

Three different luminescent silver nanoparticles(AgNPs) were synthesized by simple reduction method with the different mole ratios of L-ascorbic/citrate solution and stabilized with CTAB. The prepared three AgNPs were characterized by UV, fluorescence, FTIR, dynamic light scattering measurements and Scanning Electron Microscopy. The plasmon bands of AgNPs- reddish-brown (RB), green (G) and reddish-green (RG) were centered at 565, 587 and 592 nm, respectively. The highly luminescence emission was observed for AgNPs(G). The size diameters of the prepared AgNPs-G, RG and (RB) were measured by dynamic light scattering (DLS) method at 24.3 nm, 66.28 nm and 103.46 nm, respectively. The electrochemical properties of AgNPs-RG was recorded the oxidative part of AgNPs into Ag+ at +0.23 V and the reduction part of Ag+ into Ag0 was recorded at -0.49 V vs. Ag/AgCl). Cetyl trimethylammonium bromide (CTAB) was stabilized AgNPs(RG) which recorded in infrared and scanning electron microscope measurements. The concentration of thiourea, sodium sulphide was detected by the electrochemical sensitivity of AgNPs(RG)-CTAB. A calibration curve between electrochemical sensitivity of AgNPs-CTAB vs concentration of sulphur molecule. The limit of detection (LOD) was founded 2.10 and 1.90 µmole L-1 of sodium sulphide and thiourea, respectively (R2=0.94, n=3). The computational calculations are used to illustrated the chemical affinity of sulphur atom in sodium sulphide or thiourea towards AgNPs(RG).

A Field Evaluation of the LuciTrap and the Western Australian Trap with Three Different Baits Types for Monitoring Lucilia cuprina and Lucilia sericata in New Zealand

Flytraps can be used on farms to monitor the populations of primary strike flies (Lucilia cuprina and Lucilia sericata) and, hence, offer a view regarding the incidence of flystrike on sheep. This study aimed to contrast the specificity and effectiveness of the LuciTrap with its combination of three chemical lures (Lucilures) and the Western Australian Trap with three bait types (LuciLure, Sheep liver with 30% sodium sulphide and squid). A mean model and rate model were fitted to the data. The mean model showed no difference (p > 0.05) in the mean weekly catch for L. cuprina between the Western Australian Trap with LuciLures and the Western Australian Trap baited with sheep liver with 30% sodium sulphide (p < 0.05). Whereas, for L. sericata, no difference (p > 0.05) was found between the Western Australian Trap with LuciLures, the Western Australian Trap baited with sheep liver with 30% sodium sulphide and the LuciTrap. The rate model illustrated that the Western Australian Trap with sheep liver with 30% sodium sulphide and LuciTrap did not differ (p > 0.05) for L. cuprina and L. sericata. Combined, these results indicate that New Zealand farmers can use either the LuciTrap or the Western Australian Trap with sheep liver with 30% sodium sulphide to monitor these target species.

The development of a tannin-based after-treatment for cotton fabric dyed with sulphur dyes

Purpose Sulphur dyes provide an inexpensive medium to dye cellulosic fibres with heavy shade depths. They offer moderate to good fastness to light and wet treatments. However, owing to the environmental hazard produced by the use of sodium sulphide, the practical implication of these dyes is steadily decreasing. Moreover, these dyes are prone to oxidation causing pronounced fading on exposure to laundering. This paper aims to present the green processing of sulphur dyes by using a biodegradable reducing agent in place of sodium sulphide to dye cotton fabrics. The study also proposes after-treatments with tannin to improve the fastness properties of the dyeings. Design/methodology/approach In this study, dyeings were produced on cotton fabric with a range of C.I. Leuco Sulphur dyes, which were reduced with sodium sulphide and glucose. Sulphur dyeings were after-treated with an environment-friendly tannin-based product (Bayprotect CL (BP)); subsequently, the after-treated samples were evaluated for colour strength, wash, light and rubbing fastness. Findings A novel after-treatment method was developed, which substantially improved the wash fastness of C.I. Leuco Sulphur Black 1 dyeing to ISO 105 C06/C09 washing. However, the degree of this improvement varied for the other sulphur dyes used. The surface morphology and the possible mechanisms for the improved fastness properties were also discussed. Research limitations/implications The effect of after-treatment was significant for improving the wash fastness of sulphur black dyeings in particular, while the effect on other colours was minor. Significant improvements were observed for light and wet rub fastness for most of the dyeings, which signifies the importance of tannins as a finishing agent. Practical implications It is observed that the tannin-based product, BP, is found to provide the photoprotective effect by improving the lightfastness of the dyeings. Future research may involve the exploration of various tannins as a finishing agent to sulphur dyeings. Originality/value This novel finishing technique is found significant for improving the wash fastness of sulphur black 1 dyeings for both the reducing systems. Improvements were also observed for light and wet rub fastnesses for most of the dyeings.

Flotation of Vostok-2 skarn scheelite sulphide ore with modifiers

This paper describes the results of a study that looked at different reagent regimes of flotation of scheelite skarn ores with soda, sodium bicarbonate and sodium sulphide. According to published research data, these regimes of selective recovery scheelite from Skarn ores of Portuguese and Chinese deposits as an alternative to Petrov method. The results of studying the changes of the optical density of water glass in mixing with soda, sodium bicarbonate and sodium hydroxide at different temperatures are presented. Gelation of water glass is observed in a mixture of soda or sodium bicarbonate. The authors were studied the floatability of calcium minerals of scheelite sulphide ore by combined depressants (water glass and sodium sulphide), their dose (0–11.4 kg/t) and proportions (0.7 to 8), as well as the duration of conditioning at the Laboratory of Primorsky Concentrating Plant (PCP). In the course of research, it was established that a high dose of soda and sodium bicarbonate in the scheelite rougher flotation cycle determines a 2- to 6-times higher yield of rough scheelite concentrate with a 1.8-times lower WO3 enrichment ratio. A rise in the water dose to 1.4 kg/t in the rougher flotation cycle led to the recovery of scheelite falling to 30.4–41%, with the WO3 concentrate quality being 22.78–50.5%, corres pondingly. No commercial quality was reached when scheelite concentrate was subjected to heat treatment in a sodium sulphide (43–62 kg/t) and alkaline environment (рН 13) without water glass. Addition of 3.3 kg/t of water glass to sodium sulphide helped raise the quality of scheelite concentrate after three cleaner flotation to 54% WO3 and the recovery of scheelite was 68.4% only. A recovery of more than 82% of commercial grade scheelite concentrate (WO3 > 50%) was reached when running in standard mode using Petrov method of heat treatment. Application of the above processes, which demonstrated high performance in relation to scheelite ores taken from Skarn deposits of Portuguese and Chinese, to samples of Skarn scheelite sulphide ores from Far Eastern deposits, did not prove successful. The authors would like to thank the Research Laboratory of PCP for support with lab studies.

Sodium sulphide promoted synthesis of fused quinoline at room temperature

A novel, simple and eco-friendly strategy for the synthesis of thiopyrano[4,3-b]quinolin-1-ones and pyrrolo[3,4-b]quinolin-1-ones from 2-alkynylquinoline-3-carbonitriles and sodium sulphide (Na2S·9H2O) under catalyst-free conditions at RT.

Treatment of hide liming wastewater by carbon dioxide

Results of the investigation of hide liming process wastewater treatment by carbon dioxide are presented in a paper. Comparison of the wastewater characteristics before and after the treatment by carbon dioxide was carried out. It was attempted to regenerate sodium sulphide using three different solutions: 10% solution of sodium carbonate and 5% or 10% solution of sodium hydroxide. The kinetic of sodium sulphide concentration, general alkalinity and pH was established. The solutions with the regenerated sodium sulphide were explored for unhairing of hide. The solution of 10% sodium hydroxide with regenerated sulphides was the mostly suitable for this aim. The properties of unhaired pelt were determined and assessed.

Light fading, rub and wash fastness of sulphur-dyed cotton fabrics aftertreated with cation–tannin protective system

Purpose Sulphur dyes are the most highly consumed colourants for cellulosic substrates owing to their reasonable cost and acceptable fastness. However, the use of noxious conventional reducing agent, sodium sulphide and impaired wash fastness against oxidative bleaching is gradually decreasing the market of these dyes. As the need for “Green” goods and services is raising public awareness, this paper aims to use a glucose-based biodegradable reducing agent in place of sodium sulphide to dye cotton fabrics with a range of commercial sulphur dyes. The study also proposes an aftertreatment method to improve the fastness properties of the dyeing. Design/methodology/approach The paper investigated the impact of a newly developed aftertreatment method on the fastness properties of dyeing. This involved the sequential application of a cationic fixing agent (Tinofix ECO) and tannin (Bayprotect CL) on the coloured fabrics and subsequent evaluation of colour strength, washing, light and rubbing fastness. Findings The effect of aftertreating the dyed cotton was found to significantly improve the light and wet rub fastness. The surface morphology of the dyeing remained unaffected as depicted by the absence of any finish residues. Research limitations/implications The protective effect of the cation–tannin aftertreatments was examined with a view to providing the necessary commercial performance; however, it was established that the dry rub fastness was either reduced or remained unaffected and the wash fastness to International Organization for Standardization 105 C09 was also marginal. Originality/value This finishing technique is novel and can be found useful for manufacturing sulphur-dyed products with the improved light and wet rub fastness.