South African Journal of Chemical Engineering最新文献

This study aims to extract anthocyanins from BPF (Butterfly Pea Flower) to determine an effective solvent combination resulting in higher total anthocyanin content. Various solvent combinations were utilized to discern crucial characteristics of the obtained BPFE (Butterfly Pea Flower Extract). The BPFE from the optimal treatment was utilized as a pigment in colorimetric indicators, which were then evaluated for their initial response to seafood spoilage stored at room temperature for 24 h. The color change response of the colorimetric indicators employing BPFE pigment was compared with the pH and TVBN (Total Volatile base Nitrogen) values of the seafood initially and after 24 h. The highest total anthocyanin content was achieved with the combination of 96 % ethanol/1.5 N HCl (85:15, v/v) at 551.06 mg/L, followed by the combination of 96 % ethanol/distilled water (70:30, v/v) with pH adjustment to 1 using 1.5 N HCl at 484.27 mg/L. Subsequent combinations, in decreasing order, were 96 % ethanol/1.5 N HCl (99:1, v/v), 96 % ethanol/distilled water (70:30, v/v), and lastly, 96 % ethanol/distilled water (30:70, v/v), with total anthocyanin content of 275.53 mg/L, 200.39 mg/L, and 125.24 mg/L, respectively. BPFE applied in colorimetric indicators demonstrated responsiveness to seafood spoilage through color changes, with tested spoilage indicators being pH and TVBN. The initial (first hour) pH and TVBN values for each tested seafood were 5.5 and 9.42 mg/100 g (Scylla serrata), 6.4 and 4.23 mg/100 g (Litopenaeus vannamei), 5.4 and 11.29 mg/100 g (Uroteuthis sibogae), and 6.5 and 10.26 mg/100 g (Restrelliger kanagurta). Meanwhile, the pH and TVBN values after 24-h storage at room temperature became 7.9 and 57.01 mg/100 g, 7.4 and 76.65 mg/100 g, 7.5 and 216.44 mg/100 g, and 7.8 and 51.86 mg/100 g, respectively. The conclusion drawn is that the extraction of BPFE is more efficient when utilizing acidified ethanol solvent, and the resulting BPFE holds promise as a reliable pH indicator.

An essential nutrient that regulates growth is phosphorus. Excess phosphorus in the bodies of water causes eutrophication and impairs the quality of water resources. The supply of phosphorus is projected to be depleted in the next century since it is from non-sustainable mineral deposits. Phosphorus is extracted by the weathering of rock naturally and by the process called strip mining. One of the alternatives to sustain the phosphorus resources is to recover the phosphorus in wastewater. The study aimed to remove and recover the phosphate from SSFE wastewater by chemical precipitation. The phosphates from food establishment wastewater were successfully removed and recovered by the precipitation process using magnesium chloride as precipitant, the form of phosphorus recovered is a phosphate compound. Different SSFE wastewaters were gathered from different locations. The average removal efficiency of phosphate from SSFE 1 is 67.11 ± 0.22 % while the efficiency from SSFE 2 is 64.96 ± 0.62 % and from SSFE 3, the removal efficiency of 68.62 ± 0.48 % was obtained. The percent removal efficiencies of the three small-scale food establishment wastewater sources have no significant difference which means that the variations from the three sources of wastewater are not far from each other. The quality of the wastewater in terms of pH, DO, and phosphate content has been improved while the TDS slightly increased. Data obtained indicates that chemical precipitation can remove and recover phosphorus from SSFE wastewater. This study serves as a smart step for many food establishments to begin treating their wastewater with an alternative, inexpensive, and simple method.

Nanocrystal TiO₂ of high crystallinity (88.72 %) polymorphs have been synthesized by a unique simple route. At a low temperature under a measurable condition with differentiated hydrolysis pH of the reaction. Here titanium isopropoxide (TTIP) is used as a precursor, isopropyl alcohol (IP) is a peptizing agent and hydrolysis medium with variable pH (2.0, 2.5, 3.5, 4.5, 5.5, 7.0, 8.5, 9.5) acts as a promoter or catalyst of the reaction. We observed in the whole powder pattern fitting (WPPF) method, TiO₂ consisting of 65.0 % anatase, 68.0 % brookite and 45.0 % rutile phase in weight fraction by tailoring different hydrolysis conditions with predominant crystal plane (101), (111), (110) for the individual polymorph anatase, brookite and rutile. The crystal lattice parameters, crystal structure, volume of the crystal lattice, crystal strain, asymmetry, d-spacing and average crystallite size were also studied for the polymorph. The percent of crystallinity dominating around 54.0 to 89.0 % of the titanium and oxygen atoms are arranged regularly and periodically observed for change in the molar ratio (r) tailoring the polymorph phase stability. TiO₂ polymorph followed the blue shift at 319.00 to 336.00 nm and had good stability for the decreasing particle size (11.03 nm). This phenomenon has been revealed by transmission electron microscopy (TEM) into the polymorphs. Selected area electron diffraction (SAED) and nanobeam diffraction (NBD) showed the nanocrystal anatase with the prominent miller indices (101) and interplanar distance of 0.35 nm that was revealed by HR-TEM at the lowest pH. Nano anatase is ultrafine which was confirmed by EDS.

The synthesis of Cu(II)-doped ZIF-8/Chitosan by means of the one-pot method at room temperature was successfully carried out. The synthesized materials exhibit enhanced adsorption properties for the removal of Congo red (CR) dye. The structural and morphological properties of Cu(II)-doped ZIF-8/Chitosan were characterized. Cu(II)-doped ZIF-8/Chitosan achieved the most optimal CR removal efficiency and CR adsorption capacity (153.85 mg/g) due to its higher specific surface area (522.776 m²/g) compared to ZIF-8/Chitosan (514.882 m²/g). Electrostatic attraction, hydrogen bonding, and π-π interaction are the main interactions for the higher adsorption performance. The CR adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. The results of the thermodynamic adsorption indicated that the process of CR adsorption by Cu-doped ZIF-8/Chitosan was an endothermic reaction. The experimental results indicate that the Cu(II)-doped ZIF-8/Chitosan material has the potential to be used in wastewater treatment for the removal of anionic dyes.

Biomass conversion to value added chemicals to be used as industrial platform molecules for further synthesis of commodity chemicals has opened new window for scientists. Biomass is a lignocellulosic compound and it requires technological development since biomass is a complex molecule of linear, cyclic and aromatic hydrocarbons. Lignin being aromatic in nature can beneficial for the production of phenolic hydrocarbons. In this work conversion of Guaiacol, a model lignin compound to different aromatic hydrocarbon is performed over pure silica and alumina silica catalysts e.g. SBA-15and ZSM-5 in a fixed bed catalytic reactor. SBA-15 material was synthesized at different aging time leading to improvement in surface area and pore diameter whereas ZSM-5 was pre-treated with H₃PO₄ and KOH to modify their acidic strength. Maximum Guaiacol conversion in absence of catalyst was obtained aa 90.1 % at 550oC, 97.33 % at 550 °c in presence of SBA-15 (C) and 95.33 % in presence of P/ZSM-5, indicating the catalyst helps in enhancing the conversion, however depends on the type of catalysts and its properties like surface area, pore diameter and Lews/Bronsted acid strength. Similarly the selectivity of catechol was observed to be maximum with SBA-15 (C) as compared to other catalyst owing to its high surface area and large pore diameter. The GCMS analysis of the liquid product obtained includes Dimethyl phenol, 2-dimethoxy benzene, 2-ethyl,5-methyl phenol, catechol, Ethynylanisole and O-cresol

High-density polyethylene (HDPE), a widely used polymer globally, notably found in plastic bags, presents an environmental concern due to its non-biodegradable nature. Transforming non-biodegradable HDPE waste into a valuable resource presents a formidable ecological challenge. This research aims to study CO₂ and H₂ gases toward HDPE-based membranes through the adsorption process with pressure and temperature variation. The highest CO₂ and H₂ adsorption capacities of 14.19 mmol.g ^{− 1} (62.43 %wt) and 18.04 mmol.g⁻¹ (3.61 %wt) were obtained by pressure feeding 3 bar at 30°C. The adsorption capacity decrease as the temperature increase. At an adsorption temperature of 50°C, the adsorption capacity of CO₂ and H₂ decrease, respectively by 75.86 % and 69.81 %. The adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, and intraparticle diffusion models. The kinetic study shows that adsorption at 30°C follows the pseudo-second order. The adsorption at elevated temperatures reveals the intraparticle diffusion mechanism, indicating that the gas is adsorbed directly into the polymer matrix. Thermodynamic results include enthalpy of adsorption (ΔH), standard entropy of adsorption (ΔS), energy Gibbs (ΔG), and energy activation (E_a). ΔH CO₂ and H₂ are -22.339 and -23.654 kJ mol⁻¹, respectively, which indicates that the process is exothermic and physisorption. The ΔS value shows that the irregularity and randomness of gas movement during the adsorption process, with the respective values for CO₂ and H₂ are -0.069 and -0.072 kJ mol⁻¹ K⁻¹, respectively. ΔG for adsorption of CO₂ and H₂ with increasing temperature becomes less spontaneous, which results in decreased adsorption capacity. E_a of CO₂ is greater than H_2, so the adsorption capacity of CO₂ is smaller than H₂. The thermodynamic study shows that the adsorption process is preferable at lower temperatures.

Pyrolysis is one of the most common methods of end-of-life tires (ELTs) recycling. This study considered the use of carbon black from pyrolysis of ELTs as a carbon carrier for metals (Co, Ni, Cu, Fe) and their oxides to produce catalytic systems. The synchronous thermal analysis showed the positive effect of metal oxides/recovered carbon black (MOs/rCB) on ammonium perchlorate thermolysis. It was selected as a model catalytic reaction. Metal oxides/recovered carbon black (MOs/rCB) catalysts facilitated a reduction in the thermal decomposition phases of ammonium perchlorate, resulting in a significant narrowing of the decomposition interval. The greatest narrowing (22.7 °C) was observed at 103.5 °C for non-catalytic process. All tri-metallic catalytic systems showed high catalytic efficiency, providing a narrowing of the decomposition interval on average 2.5 times more in comparison with mono-metallic catalysts. Trioxide catalyst CuO/CoO/FeO/rCB showed the most significant shift in the high-temperature decomposition stage by 13% (from 334.0 °C to 293.2 °C). The activity of di-, tri-, and tetra-metallic catalytic systems was further enhanced by the synergistic effect induced by the addition of a second (or more) metal to the system. Efficient use of rCB for impregnated catalyst systems production could improve the economic efficiency of ELTs pyrolysis.

Methylene Blue (MB) is a thiazine group dye frequently used in the textile industry but the difficulty in degrading its molecule poses a significant risk of toxicity to humans. Gloeophyllum trabeum, a brown-rot fungus, has been previously shown to degrade MB. However, the decolorization capacity achieved was relatively poor due to the extended incubation time. This study aimed to improve the MB degradation process by G. trabeum with the addition of Ralstonia pickettii bacteria. The concentrations of R. pickettii added included 2, 4, 6, 8, and 10 mL (1 mL ≈ 1.39 × 10⁸ CFU), while the degradation process was conducted at 30 °C within a 7-day incubation period. The results showed that the highest decolorization percentage was obtained with the addition of 10 mL R. pickettii. The mixed cultures decolorized MB by approximately 85%, while G. trabeum achieved 11% decolorization. The metabolite product produced from the process included C₁₂H₁₃N₃O_6, C₁₄H₁₄N₃S, C₁₂H₁₁N₃SO₆, C₁₂H₁₁N₃SO₇, and C₂₂H₁₅N₃SO₅. Therefore, it was concluded that R. pickettii could enhance the capability of G. trabeum to decolorize MB.

There is a need to improve cobalt and nickel recovery from industrial waste streams such as secondary leach solutions and rechargeable battery leach solutions due to the increasing economic value of these critical metals. Ammonia is an important lixiviant due to its limited environmental impact compared to acid based lixiviants, however, the subsequent selective extraction of cobalt and nickel from the leach liquor is a major challenge. This study presents new experimental findings on the treatment of a Base metal Refinery (BMR) secondary leach liquor that contains high concentrations of ammonia and ammonium sulphate, and low concentrations of cobalt (∼442 mg/L) and nickel (∼1624 mg/L) using partially saponified Cyanex 272. New knowledge that can be applied in the treatment of ammonia based leachates from various industrial wastes that contain residual cobalt and nickel is presented herein. The investigation was conducted through the determination of the optimum extraction temperature, percentage saponification, and organic to aqueous ratios. Partial saponification of Cyanex 272 increased ammonia-metal complex stability at the interphase and this limited cobalt extraction between 30 °C and 50 °C. However, a high cobalt extraction percentage, and a high separation factor of 94.07 %, and 1189.76 respectively were achieved at 60 °C, 20 % saponification, and 0.5 O/A loadings in a single contact. A second-stage batch extraction produced a nickel aqueous stream with no cobalt. Stripping of the loaded organic phase with dilute sulphuric acid produced a pure cobalt aqueous stream. Further, the extractant was successfully regenerated post stripping. Overall, partial ammonium-saponification increased the extent of cobalt extraction, and selectivity. The novel process conditions reported herein can be used to design sustainable cobalt-nickel separation processes.

This research explores the extraction and application of cellulose fibers from various parts of plants, specifically young and old stems, as well as seed/fruit skins. The primary focus was on the effective removal of lignin and other extraneous compounds to enhance the properties of cellulose fibers for their subsequent use as fillers in the production of porous composites. These composites were evaluated for their responsiveness to ammonia vapor through a color change test, indicating their potential as intelligent, environmentally friendly packaging materials. The cellulose fibers were isolated through a two-stage process involving delignification using 20 % sodium hydroxide (NaOH) and bleaching with a 5 % hydrogen peroxide (H₂O₂) and 3.8 % NaOH mixture. These fibers were then characterized using Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffractometry (XRD), and Scanning Electron Microscopy (SEM). The analysis revealed that fibers extracted from the younger stem bark exhibited superior characteristics, notably in their crystallinity index (CI), which was 5.16 % higher than that of fibers from other plant parts. Surface morphological studies indicated that the cellulose fibers derived from CG plants possess a hollow shape. When used as fillers, these fibers contributed to the enhanced porosity of polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) composites. SEM analysis further demonstrated that the inclusion of fibers with higher degrees of crystallinity significantly increased the composites' porosity. Additionally, composites immobilized with anthocyanins from the Butterfly Pea Flower (BPF) exhibited a notable colorimetric response to environmental pH changes. Thermogravimetric analysis suggested that incorporating these fibers into the composite matrix improves thermal stability. The study's findings underscore the potential of these porous composites as colorimetric indicators, paving the way for their application in smart, eco-friendly packaging solutions.