Sodium Metabisulfite Research Articles

One‐Pot Synthesis of C‐Substituted bis‐Benzimidazoles and Benzobisimidazoles via Reductive Cyclization of o‐Nitroaniline Derivatives and Aldehydes using Sodium Metabisulfite in a Microwave Reactor

AbstractHerein, we report a simple and an economical method to synthesize C‐substituted bis‐benzimidazole and C‐substituted benzobisimidazole derivatives in moderate to excellent yields using sodium metabisulfite, under microwave irradiation conditions. The most attractive feature of the methodology is the three‐step yet one‐pot condensation of nitroarenes with various benzaldehyde derivatives to synthesize useful benzimidazoles, and an easy product isolation method by simple solvent trituration techniques. The methodology can be fine‐tuned to synthesize selectively the mono C‐substituted benzimidazoles, leaving a nitroaniline functionality intact for preparing a variety of unsymmetrical C‐substituted bis‐benzimidazoles.

Synthesis and characterization of novel electrospun nanofibers based on taro starch: influence of solvent and isolation agent on morphology and diameter

AbstractThe utilization of natural polymers in producing electrospun nanofibers has received significant attention due to their biocompatibility, sustainability and diverse range of applications. This research focuses on synthesizing electrospun nanofibers derived from taro starch isolated from tubers. The investigation utilized SEM to examine the structure and size of the electrospun nanofibers. Formic acid and dimethyl sulfoxide solvents were tested to determine the most efficient solvent system for synthesizing taro starch nanofibers. The results demonstrated that the taro starch nanofibers can be effectively synthesized when using formic acid as the primary solvent. The study also investigated the impact of altering the volumetric ratio of formic acid to water on nanofiber morphology and size, finding that a lower formic acid fraction produced smooth fibers while a higher fraction resulted in fused fibers. The electrospinnability was further evaluated by comparing the effects of different isolation agents—distilled water and sodium metabisulfite—during the isolation process. The isolation agent significantly affected the fiber diameter, with notable differences observed in the smoothness of taro starch nanofibers at starch solution concentrations of 13, 15 and 17 wt%. Overall, the results of the study showed that the formation of taro starch fibers was influenced by the type of solvent, the volume fraction of the solvent to water, and the starch isolation agent. Successful fabrication of nanofibers from taro starch and its optimization parameters can contribute to the development of environmentally friendly nanofiber materials and offer a variety of applications in biomedicine, food and environmental engineering, such as tissue engineering, wound dressing, drug delivery, functional food delivery and food packaging. © 2024 Society of Chemical Industry.

Sodium Metabisulfite Mediated Synthesis of Bis(pyrazolo[1,5-a] pyrimidin-3-yl)methanes from Pyrazolo[1,5-a]pyrimidines with Dimethyl Sulfoxide as a C1 Synthon

AbstractWe report an unprecedented synthesis of bis(pyrazolo[1,5-a]pyrimidin-3-yl)methanes, a new class of di(hetaryl)methanes, from pyrazolo[1,5-a]pyrimidines by using DMSO as a C1 synthon (methylene source). The transformation is mediated by sodium metabisulfite (Na2S2O5), which plays a crucial role in the presence of acetic acid as a promoter. A wide variety of bis(pyrazolo[1,5-a]pyrimidin-3-yl)methanes were synthesized in moderate to good yields of up to 90%. Mechanistic studies suggested that the reaction follows an ionic pathway, probably involving a methyl(methylene)sulfonium ion as an active electrophilic species formed in situ by the reaction of DMSO with Na2S2O5.

Pyrite Depression by Sodium Metabisulfite in Freshwater and Seawater with Copper Activation

Pyrite has natural floatability and thus readily enters valuable mineral flotation concentrates, diluting their quality and decreasing their economic value. Its separation is challenging, depending on process conditions, the presence of activating ions, and water quality, particularly in regions where seawater is used. This study examines the effect of various doses of sodium metabisulfite (SMBS) on pyrite depression in freshwater and seawater under weakly alkaline conditions and with different copper ion concentrations. Without the addition of activators or depressants, pyrite recovery is 40% in freshwater and 60% in seawater, whereas with 10 ppm of SMBS, recoveries drop to 28% and 38%, respectively. The addition of 10 ppm Cu2+ increases recovery by 10% in freshwater and by 20% in seawater. In the presence of 75 ppm of PAX, maximum recovery reached 50% in freshwater and 80% in seawater. These results suggest that cationic bridges formed by seawater ions, combined with CaOH+ activation, play a critical role in pyrite activation, even in the presence of depressants.

Comparative assessment of fresh and processed tomato (Solanum lycopersicum) pulps: Impact of processing on physicochemical, antioxidant, and enzymatic behavior

This study investigated the impact of chemical and thermochemical treatment on the physicochemical, antioxidant, and enzymatic behavior of tomato pulp. The chemical treatment involved the use of 0.05 % potassium metabisulfite, 0.05 % sodium metabisulfite, 0.05 % potassium sorbate, 0.05 % sodium benzoate, 0.5 % ascorbic acid, and 1 % citric acid, whereas the thermochemical treatment involved heating the tomato pulp to 80–82 °C for 30 min before applying the same chemical preservatives, followed by storage at 30±1 °C for 120 days. The results revealed that the thermochemically treated sample retained higher levels of total phenol content (6.24–4.10 mgGAE/100 g), vitamin C (136.43–54.05mg/100 g), and a lower level of lycopene content (59.87–43.28µg/100 g) compared to chemically treated samples. Additionally, the thermochemically treated sample had higher TSS (6.57 to 6.70°Brix), increased acidity (1.60 % to 1.06 %), lower pH (4.11–3.57), better color stability, and reduced browning. Moreover, it showed improved oxidoreductase and hydrolase enzymatic control during storage. Therefore, the idea of thermochemical treatment can be a milestone in improving the shelf life of tomato pulp to benefit the food industry.

Iodine/DMF-Mediated Regioselective Sulfenylation Using Arenediazonium Tosylates and Sodium Metabisulfite: An Easy Access to 3-Arylthioindoles.

A practical C3 sulfenylation of indoles has been accomplished using arenediazonium tosylates and sodium metabisulfite, with a key role of iodine/DMF combination in the reaction. The method involves scarce use of sodium metabisulfite as a divalent sulfur source and offers an array of structurally diverse 3-arylthioindoles in high yields under operationally simple transition-metal-free and mild conditions.

Association of SO2-Generating Pads before Packaging and during Cold Storage to Extend the Conservation of 'Italia' Table Grapes.

The SO2-generating pads contain different concentrations of sodium metabisulfite, which absorbs water from the grapes' transpiration, releasing SO2 gas, and there are slow-(SlowSO2) and dual (DualSO2)-releasing pads (fast release in the first 48 h and slow for up to 60 days). The ultra-fast SO2-generating pad (FieldSO2) releases the SO2 quickly for up to 6 h, and it was designed to be used soon after the harvest and until the grapes' packaging. The goal was to study the effect of FieldSO2 associated with SlowSO2 and DualSO2 pads on gray mold incidence and physicochemical and appearance characteristics of 'Italia' table grapes. Grapes were harvested from a commercial vineyard in Parana, Brazil, in 2020 and 2021, and packaged in cardboard boxes, and the treatments were as follows: control (without SO2-generating pads); FieldSO2 + SlowSO2; and FieldSO2 + DualSO2. After 30, 45, 60, 75, and 90 days of cold storage (1 ± 1 °C), the grapes were assessed for gray mold incidence, mass loss, shattered berries, stem browning, and filamentous fungi on the surface. The use of FieldSO2 associated with SO2-generating pads is effective in controlling gray mold on 'Italia' table grapes, especially the treatment FieldSO2 + DualSO2, which provides the lowest incidence of the disease up to 90 days of cold storage, while the combination with SlowSO2 results in intermediate efficacy. Treatments combining these SO2-generating pads extend the postharvest shelf life of 'Italia' grapes, with few shattered berries, low mass loss and freshness of the rachis without impairing the bunch's appearance.

Antisickling, hemolytic activities and toxicological evaluation of three plants species from the Nigerien Pharmacopoeia: Annona senegalensis Linné. Boscia senegalensis (Pers) Lam. and Ampelocissus afr

The aim of this study consits to evaluate the antisickling and antihemolytic activities and to determine the subacute toxicity of three plants Annona senegalensis L.; Boscia senegalensis (Pers) Lam.; and Ampelocissus africana (Lour) Merr.. The plant material contains leaves and bark of Annona senegalensis roots, leaves and bark root of Boscia senegalensis and the roots of Ampelocissus africana. A single method (80% ethanol maceration) is used to extract the five samples. The antisickleemic and antihemolytic effects are established with sickle cells disease (SCD) in the presence of sodium metabisulfite. Subacute toxicity is tested on Wistar strain rats. All samples showed an antisickling effect but leaves of Annona senegalensis (LAS) showed the highest percentage of antisickling activity (89.55%) at 50mg/ml. The anti-hemolytic effect was demonstrated in all samples by inhibition of hemolysis in the presence of a hemolysant. The toxicity results showed that the aqueous extracts of Annona senegalensis leaves and Boscia senegalensis root bark have non-toxic effects to wistar strain rats. However, some manifestations including fatigue, stretching and slight dyspenea were observed at doses of 150mg/mL and 300mg/mL. This work can contribute as a starting point towards the development of an improved traditional medicine (ITM) method which can help to treat the sickle cell disease. Keywords: Annona senegalensis L., Boscia senegalensis (pers) Lam and Ampelocissus Africana (Lour) Merr. Antisickness activity, Toxicity.

INVESTIGATION OF RARE AND RARE-EARTH ELEMENTS LEACHING PROCESSES FROM THE WEATHERING CRUST ORES OF THE KUNDYBAY DEPOSIT

The weathering crust ore of the Kundybay deposit is a hard-enriched ore that contains such minerals as cherchite, bastnesite, kaolinite, etc., which are embedded in the matrix structure of other silicate rocks. These minerals contain rare earth (RE) and rare earth elements (REE). The multi-component structure and dense packing of minerals in the aluminosilicate matrix of the ore make it difficult to be blocking out. Determination of the optimal ore blocking method in order to extract RE and REE is an urgent task for today. The purpose of this work is to develop an effective method of leaching RE, REE and "white soot" from the weathering crust ores of the Kundybay deposit. Methods. Processing with soluble ammonium, magnesium and aluminium salts will allow estimation of the state of RE and REE in the ore. The indicator of RE and REE blocking out during leaching with sodium hydroxide is the transfer of silica into solution, due to which RE and REE form their own hydroxides, which can be subsequently transferred into solution by acid treatment. Acid leaching with sodium pyrosulfite, hydrofluoric acid and sulfuric acid will allow the RE and REE to be immediately transferred into solution. Results and Discussion. The main characteristics of the Kundybay deposit weathering crust ore were determined, such as: silica content, moisture content, base metals, RE and REE. Conclusion. The degree of extraction of RE and REE by soluble salts of ammonium, magnesium and aluminium did not exceed 2%, which indicates the existence of RE and REE in the form of their own minerals. Leaching with sodium hydroxide showed low recovery of silica, with RE and REE remaining in a difficult-torecover form. Leaching with a mixture of sodium pyrosulfite, hydrofluoric and sulfuric acids is a promising method for RE and REE recovery due to the complex effect of the components of this mixture.

Effect of Aloe vera Gel and Sodium Metabisulphite on Expression of Fibroblast Growth Factor in Incision Wound of Rats

An incision wound is a wound caused by being sliced. Two ingredients that play a key role in the wound-healing process are glucomannan and acemannan, which are rich in polysaccharides and growth hormones. Growth hormones stimulate fibroblast activity and proliferation. The present study involved 35 Sprague Dawley male rats, aged 2-3 months old and weighing 200-300 grams. The study comprised seven groups including, negative control group (G1), positive control (aquades, G2), betadine 10% (G3), gel base (0.5 mg, G4), gel base + sodium metabisulfite 0.2 gr (G5), gel base + Aloe vera 5% (G6), and gel base + Aloe vera 5% + sodium metabisulfite 0.2 gr (G7). Each group had five replications. Initially, a 4-cm incision was made on the dorsal skin of each rat. The study lasted 15 days with observations made on days 3, 7, and 15. After the observation period, the rats were anesthetized and then terminated to collect skin tissues for microscopic examination. The tissue samples were then stained immunohistochemically to assess fibroblast growth factor (FGF) expressions. The results showed that the highest FGF expression was observed in the 5% Aloe vera + 2% metabisulfite group (G7), while the lowest FGF expression was in the negative control group (G1). It is concluded that Aloe vera L. extract gel at 5% + 2% metabisulfite (G7) significantly enhances the expression of FGF. Keywords: Aloe vera L, Fibroblast growth factor, Incision wound, Skin, Sodium metabisulfite

496 Effects of sodium metabisulfite (SMBS) and SMBS-containing lipid microparticles on the performance and intestinal barrier functions of weanling piglets challenged by deoxynivalenol-contaminated diets

Abstract This study aimed to investigate the effects of sodium metabisulfite (SMBS) and SMBS-containing hydrogenated palm oil (HS) microparticles on the growth performance and intestinal barrier functions of weanling piglets challenged by deoxynivalenol (DON)-contaminated diets. Four corn-soybean-meal based diets were used: 1) negative control (NC, 0.00 mg/kg of DON); 2) positive control (PC, 3.3 mg/kg of DON); 3) SMBS (PST, 3.3 mg/kg of DON and 0.2% of SMBS); and 4) HS microparticles (HST, 3.3 mg/kg of DON and 0.45% of HS microparticles). Weaned piglets (n = 40) with similar body weights (BW; 8.22 ± 0.39 kg, 10 pigs/treatment) were fed for 28 d, including a 1-wk adjustment and 3 wk for exposure. Piglets subjected to the PC diet exhibited a noteworthy reduction in final BW by 13.3%, average daily gain (ADG) by 21.4%, and average daily feed intake (ADFI) by 20.1% compared with those on the NC diet (P < 0.05). Compared with the PC diet, the PST and HST diets increased by 6.76% and 4.31% in final BW (P < 0.05), 13.6% and 8.60% in ADG (P < 0.05), and 9.15% and 9.71% in ADFI (P < 0.05), respectively. No significant differences were detected in these values between the NC, PST, and HST diets (P > 0.05). There were no significant variations observed in the feed conversion ratio (FCR) among the four dietary treatments (P > 0.05). Feeding the PC diet to piglets led to a significant increase in the fecal score compared with the NC and HST diets (P < 0.05). No significant differences were detected in the mRNA expression levels of nutrient transporters and tight junction proteins among these four diets (P > 0.05). Additionally, compared with the NC diet, the PC diet significantly increased the mRNA abundance of Interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, and toll-like receptor 4 (TLR4; P < 0.05); however, a decreased mRNA abundance of IL-8 and TNF-α was observed in the pigs fed the HST diet (P < 0.05), indicating that the encapsulated SMBS from the HS microparticles could have the potential to mitigate the effects of DON. Overall, adding 0.45% of HS microparticles to a 3.3 mg/kg DON-contaminated diet in piglets could maintain the growth performance, and using the HS microparticles revealed some potential in DON detoxification by reducing the gene expressions of pro-inflammatory cytokines.

Keeping quality of raw ground beef patties fortified with polyphenols extracted from Acacia mearnsii bark and leaves

Acacia mearnsii byproducts are naturally endowed with a plethora of diverse polyphenols that exhibit antioxidant properties indicating potential application in enhancing oxidative shelf-life of perishable foods. The current study evaluated the oxidative shelf-life of raw ground beef patties fortified with 450 μg/g of polyphenolic extracts from A. mearnsii bark (AMBE) or leaves (AMLE) compared to positive (sodium metabisulphite; SMB) and negative (no extract; CTL) controls for 9 d at 4 °C in a simulated retail display. The AMBE had higher (P ≤ 0.05) contents of proanthocyanidins, and total phenols, flavonoids and tannins, and consequently demonstrated greater (P ≤ 0.05) in vitro antioxidant activity than AMLE. The polyphenolic extracts increased (P ≤ 0.05) antioxidant activity in beef patties compared to the CTL though they were outperformed (P ≤ 0.05) by the SMB. Fortification of beef patties with the polyphenolic extracts, particularly AMBE, delayed colour deterioration and oxidation of myoglobin during retail display relative to the CTL but were less efficient than SMB (P ≤ 0.05). Beef patties fortified with the polyphenolic extracts and SMB had comparable (P > 0.05) peroxide values, TBARS and p-Anisidine values which were all lower (P ≤ 0.05) than those for the CTL patties. The order of protein thiol content in beef patties was as follows: CTL ≥ AMLE ≥ AMBE ≥ SMB (P ≤ 0.05). Findings suggest that A. mearnsii-derived polyphenolic antioxidants, particularly AMBE has great potential to extend oxidative shelf-life of raw beef patties.

Effect of sodium metabisulfite treatment and storage condition on metabolic profile of young coconut (Cocos nucifera L.)

Young coconuts (Cocos nucifera L.) used for export are trimmed to reduce their size and weight to lower transport costs. However, trimmed coconuts have a shorter shelf life due to microbial spoilage and surface discoloration caused by enzymatic browning. To minimize these effects, trimmed coconuts were dipped in an anti-browning agent, sodium metabisulfite (SMB), and stored under ambient conditions. However, there have been no reports on the effects of SMB treatment on metabolome changes in the flesh and water of young coconuts. Hence, this study investigated the metabolite changes in trimmed young coconuts after SMB treatment under different storage conditions using a gas chromatography (GC)/mass spectrometry (MS) metabolomic profiling approach. Tall young coconut samples were trimmed and treated with a 2% SMB solution for 5min before storage at 25°C or 4°C for 2-4 weeks. Coconut flesh and water samples were collected after storage for 0, 2, and 4 weeks, and were subjected to GC-MS analysis. The results showed that the major metabolites affected by coconut deterioration were amino acids, sugars, and sugar alcohols. SMB treatment and/or refrigeration can help prevent metabolite changes in the flesh and water of young coconuts. In the future, improvements in storage conditions based on metabolite profiles should be explored.

Microneedles mediated-dermal delivery of Vitamin C: Formulation, characterization, cytotoxicity, and enhancement of stability

Vitamin C (VIT C) is an antioxidant that prevents skin aging. Although dermal delivery is one of the most effective routes to transport VIT C to the skin, the impact of this route can be limited by the barrier function of the stratum corneum (SC). Additionally, VIT C rapidly oxidized and degraded under light and temperature. Therefore, this study provides an approach to utilizing microneedles (MNs) to improve the dermal delivery of VIT C and enhance its stability by incorporating a stabilizing system of ethylenediaminetetraacetic acid (EDTA) and sodium metabisulfite (Meta) within the MNs. Vitamin C microneedles (VIT C MNs) were fabricated using different biodegradable polymers and various concentrations of EDTA/Meta. VIT C MNs were evaluated for morphology, VIT C content, mechanical properties, dissolution rate, needles’ insertion, physicochemical properties, ex vivo permeation, viscosity of VIT C polymeric solutions, cytotoxicity, and stability. The results showed that VIT C MNs were uniform and mechanically strong. The recovery of VIT C in MNs was 88.3–90.0 %. The dissolution rate of MNs was <30 min. The flux of VIT C varied based on the composition of MNs. VIT C MNs demonstrated safety against human dermal fibroblasts. VIT C MNs with EDTA/Meta (0.1/0.3 %) were stable under different storage conditions for two months. In conclusion, VIT C MNs were successfully developed using biodegradable polymers, and the stabilizing system (EDTA/META) provided a stable dermal delivery system for VIT C to protect skin from aging.

Sorbic acid is an efficient preservative in pea-based meat analogues

The popularity of plant-based alternatives to meat has increased due to advancements in important attributes such as taste. Using adequate processing at elevated temperatures combined with aseptic packaging, especially in combination with storage below the freezing point, microbial hazards in these products are negligible. However, for plant-based alternatives to ham, sausages, spreads, or cheese, for example, on sandwiches, the product must withstand microbial growth in the fridge after breaking the seal of the food packaging, as everything is not typically consumed directly. Currently, there are few preservations methods, but one solution is adding weak acid preservatives, with less inherent health concerns compared to sulfites and nitrite, e.g. carcinogenicity and hypersensitivity. To be fully effective an acidic pH is required. In this study, an approach where sausage-resembling meat analogues with different pHs (4.14–5.56) were prepared without preservatives, with potassium sorbate (2000 mg/kg), or sodium disulfite (200 mg/kg), and thereafter subjected to standardised challenge tests to elucidate the efficacy. Sorbate was the only preservative effective to prevent growth of all tested organisms, Penicillium roqueforti, Pichia fermentans and Listeria monocytogenes. The identified superiority of sorbate compared to other tested preservatives is relevant knowledge when developing preservation strategies for other types of meat analogues.

Exploring the anti-diabetic activity of benzimidazole containing Schiff base derivatives: In vitro α-amylase, α-glucosidase inhibitions and in silico studies

The current study explores the anti-diabetic potential of some Schiff bases containing benzimidazole scaffold. These derivative were synthesized by refluxing sodium metabisulfite with ethyl 2-(2-ethoxy-6-formylphenoxy)acetate followed by the addition of ortho phenylene diamine in DMF solvent to get the benzimidazole which was further refluxed in hydrazine hydrate to obtain the hydrazide. Finally various substituted benzaldehydes were treated with the desired hydrazide using a catalytic quantity of acetic acid to obtain the hydrazone Schiff bases. These compounds were evaluated for their ability to inhibit α-amylase and α-glucosidase inhibitory potentials. Among them, six derivatives including 2g, 2h, 2q, 2p, 2i, and 2m displayed noteworthy inhibitory activities against α-amylase (IC50 = 2.15 ± 0.17 µM to 15.18 ± 3.29 µM ) and α-glucosidase (IC50 = 4.21 ± 0.78 to 16.10 ± 0.52 µM) superior than the standard acarbose, while the remaining compounds showed significant to less inhibitory activities. By clarifying the mechanisms of interaction between the chemicals and amino acid residues, the molecular docking analysis attempted to shed light on the binding modalities of these molecules. The reactivity indices of these compounds were calculated using the Density Functional Theory (TD-DFT) approach, employing the B3LYP-d energy function and lacvp**(d,p) basis set for calculations. Schiff base derivatives based on benzimidazole, especially compounds 2h and 2g, exhibited lower electrophilicity and higher bioactivity compared to their counterparts 2i and 2m.

THE EFFECTIVENESS OF CORN SILK EXTRACT AGAINST DENTAL CARIES-CAUSING BACTERIA AND ITS FORMULATION IN MOUTHWASH PREPARATION

Indonesia is undergoing a dental caries emergency with a prevalence of 51.1% (Riskesdas, 2018). This may cause tooth decay due to dental plaque bacteria such as Streptococcus mutans. Mouthwash can be a solution because it has antibacterial properties and reaches interspaces on the teeth. Unfortunately, the active ingredient of mouthwash, chlorhexidine, can cause cancer-related mutations if used continuously. Therefore, it requires alternatives to natural ingredients, such as corn silk. The research aims to determine the corn silk phytochemical profile and minimum inhibitory concentration (MIC) against Streptococcus mutans. The research started by macerating corn silk simplicia using 70% ethanol. Afterwards, thin layer chromatography (TLC) was conducted to determine its phytochemical profile. Disk-diffusion and broth microdilution methods were conducted using various concentrations of corn silk extract to determine its antibacterial activity and minimum inhibitory concentration (MIC) against Streptococcus mutans. Then, the MIC₅₀ was used as the minimum dose of corn silk extract concentration in mouthwash formulation which qualities controlled by pH and organoleptic tests. The yield of corn silk extracted was 16.17%w/w. The phytochemical profile from TLC showed that flavonoids, tannins, and terpenoids were present. Corn silk extract has antibacterial activities against Streptococcus mutans with MIC₅₀ of 7.2%w/v. Corn silk extract, tween 80, sorbitol, sodium benzoate, sodium metabisulfite, oleum menthae piperitae, and distilled water were used in four mouthwash formulas (F1-F4). The pH of all formulas was 5 and the organoleptic test showed that from 30 panelists, the majority chose F2 as the best in terms of taste, color, and smell.

Effect of packaging and storage conditions on the pasting and functional properties of pretreated yellow-fleshed cassava flour

Cassava is highly susceptible to post harvest physiological deterioration which makes it necessary to initiate processing so as to extend the shelf life. In order to improve and enhance the nutritional characteristics of the processed cassava flour, this research was carried out so as to evaluate the adequate packaging materials and storage conditions necessary for safe storage and good flour quality. Pasting properties of food/flour is an indication of the different applicability of starch-based food ingredients in product development. The effect of packaging materials (cylindric polyvinyl containers and aluminum ziplock pouch bags) on quality attributes of pretreated yellow-fleshed cassava flour (YFCF) samples stored in two storage conditions a (cooling chamber at 5 °C and 30 % relative humidity and; in a climate chamber at 30 °C and 50 % relative humidity) was investigated for 8 weeks. Flour samples from each package type were evaluated for water absorption capacity, pasting and oil absorption capacity fortnightly. The treated initial flour sample before storage-sulfured (BSS) had the highest peak viscosity (891 RVU). The low peak time at the end of storage in non-sulfured flours packed in aluminum pouch bags and stored at 5 °C is an evidence of time and energy saving capacity. The water absorption capacity of non-sulfured flour samples packed in cylindric polyvinyl containers and the sulfured flour sample packed in an aluminum pouch bag at 30 °C increased with storage duration. The aluminum ziplock pouch bags showed excellent storage quality and retained better pasting property. The climatic storage condition revealed better keeping quality. The use of sodium metabisulphite revealed its suitability as a pretreatment tool.

Recycling Process of Spent Alkaline and Zn-C Batteries for the Re-Utilization in Rechargeable Zn-Ion Battery

The Zn, Mn and C extraction processes from spent primary batteries and the synthesis of recycled Zn film, MnO2 and MnO2/C for Zn-ion battery application were developed in the project. The Zn, Mn and C extraction process involved the acid leaching of Zn and Mn ions from the spent alkaline and Zn-C battery electrodes in the lab-scale was initially investigated using various leaching conditions. The acid leaching using 0.5-2 M HCl and H2SO4 at ambient temperature providing Zn extraction efficiencies in a range of 72.3-95.3%. By introducing an inexpensive reducing agent namely sodium sulfide (Na2S), sodium metabisulfite (Na2S2O5) or hydrogen peroxide (H2O2) in 2M H2SO4, the Mn extraction efficiency for Mn was increased from 21.9% (with no reducing agent) up to 48.4%, 82.8% and 98.9%, respectively. The upscale leaching study was subsequently performed in a 100-L pilot scale reactor demonstrated the Zn and Mn extraction efficiencies of 71% and 65%, respectively. Using the leaching solutions from the upscale hydrometallurgical route, Zn-film fabrication via electrodeposition process, and the MnO2 and MnO2/C synthesis via hydrothermal techniques were performed. Additionally, the one-step synthesis of MnO2/C via one-step hydrothermal method with no acid leaching was also explored in this study. The recycled Zn, MnO2, MnO2/C and C residual were subsequently used as the anode and cathode main components in the CR2032 and pouch-cell rechargeable Zn-ion batteries. The recycled MnO2 and MnO2/C provided similar performance as the commercial products, which indicating the recycled MnO2, MnO2/C could be effectively utilized in the Zn-ion battery, while the utilization of recycled Zn-film provided slightly lower performance compared to that of the commercial Zn foil.

GOLD RECOVERY USING CITRUS SINENSIS PEELS AS BIOADSORBENT

The recovery of gold from electronic waste using locally available and environmentally friendly materials were investigated. Bio-adsorbent for gold recovery was prepared from Citrus sinensis peels through mechanical processing and chemical modification. Some ceramic computer processor units were leached using aqua-regia as lixiviant. Gold was recovered from the solution using the prepared bio-adsorbent and Sodium Meta Bisulphite (SMB). The recovery efficiency of the bio-adsorbent was determined and results compared to that of SMB. The adsorption of gold at different contact times was determined and the concentration of gold in solution was found using Agilent 4100 Micro Plasma Atomic Emission Spectroscopy (MP-AES). The results obtained showed that the bio-adsorbent has an adsorption capacity of 98.4% for gold and an adsorption kinetics correlation coefficient of 0.99989. This is comparable with SMB which has 95.4%. adsorption capacity and an adsorption kinetics correlation coefficient of 0.98597. The higher adsorption capacity of the bio-adsorbent is attributed to the binding sites and the chemical modification which increases the reducing properties of the functional groups present in the Citrussinensis peels.