Case Studies in Chemical and Environmental Engineering最新文献

The current study successfully reported biosynthesized silver nanoparticles (bio-AgNPs) using an efficient green route, employing Archidendron bubalinum pods extract as reducing and stabilizing agent under sunlight irradiation. A. bubalinum pod extract contains several fatty acid macromolecules, such as palmitic acid, stearic acid, cinnamic acid, and oleic acid. Those compounds contain hydroxyl and carboxyl groups, which play a crucial role in the reduction process of Ag ions to form Ag nanoparticles. UV–Visible spectrophotometry confirmed the formation of bio-AgNPs. The Energy Dispersive X-ray spectroscopy (EDS) and X-ray Diffraction (XRD) also supported the bio-AgNPs formation, consisting of 67.42 % of Ag in a crystalline form. Meanwhile, the materials size was confirmed by Dynamic Light Scattering (DLS), resulting in an average size of 58.9 ± 7.6 nm. This result aligned with Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), and was confirmed that the material had spherical AgNPs capped with a thin layer. Moreover, this method resulted in stable bio-AgNPs with a surface charge of −32.4 ± 0.35 mV that were stable for over 3 months. Further, the materials were tested against Staphylococcus aureus ATCC6633 and Gram-negative Escherichia coli ATCC6633 bacteria using inhibition test, MIC, and MBC, demonstrating a good inhibition.

This study presents a novel composite nanofiber membrane combining polyacrylonitrile/polyvinylidene fluoride (PAN/PVDF) electrospun nanofibers with locally sourced zeolite from Sumatera, Indonesia, for pollutant dye filtration. The Ze-PAN/PVDF composite nanofiber membrane has 100% methylene blue dye rejection even after five filtration cycles with a permeation flux of 185 L m⁻² h⁻¹ bar⁻¹. The membrane is highly selective, with 100% dye filtration efficiency for cationic dyes (i.e., methylene blue and crystal violet) vs. 78% and 1% for anionic dyes (i.e., Congo red and methyl orange, respectively). For the cationic dyes, the dye filtration mechanism is mainly governed by electrostatic attraction, while the size exclusion mechanism becomes more dominant for the anionic dyes. Overall, these results demonstrate the potential use of Ze-PAN/PVDF composite nanofiber membrane in wastewater treatment applications.

Elimination of plastic waste deposition in landfills is essential to avoid secondary pollution such as microplastics. Under appropriate environments, methanotrophs which proceed through methane oxidation reaction are capable of degrading plastics via their co-metabolisms. Nevertheless, nutrient conditions in landfills to promote methane oxidation and plastic degradation are still unclear. Therefore, the biodegradation of plastic wastes under semi-aerobic conditions with methane oxidation activities and nutrient additions was examined in this study. Various types of plastics (HDPE, LDPE, oxo-degradable plastics) were exposed to methane and air under semi-aerobic conditions in lysimeters where methanotrophic activities were promoted. Nitrate and phosphate and their combination were introduced into waste mixtures to determine their effect on plastic biodegradation. Changes in gas compositions, plastic weight losses, by-products, and microbial consortium were studied. Phosphate supplement resulted in higher methanotrophic population, particularly that of type I (Methylococcus sp., Methylocaldum sp., Methylovorus sp., Methylomonas sp., and Methylobacter sp.) and yielded highest biodegradation for oxo-degradable (15-20%) followed by HDPE (15-19%), and LDPE (4–7%). The plastic degradation was found well correlated to methane oxidation rate. Oppositely, nitrate supplements reduced MOR due to their competition with oxygen for microbial reactions. Semi-aerobic condition with a phosphate supplement is found effective in promoting plastic degradation in landfills.

The presence of harmful chemicals in water is a major problem in many regions worldwide. This study aimed to develop a nanocomposite of carbonised-chili and nanoparticles to remove nickel ions (Ni(II)), methylene blue (MB) and paracetamol (PARA) from water. The material was characterised by TEM, FTIR, XRD and TGA. The uptake for PARA and MB was endothermic with capacities of 39.98 and 44.31 mg/g at pH value 7, while that of Ni(II) was exothermic at 56.06 mg/g at pH value 5. The data were described by the Freundlich and PSO models. The reusability was tested up to four cycles. In conclusion, a low-cost nanocomposite adsorbent developed from chili carbon/Fe₃O₄ exhibited excellent adsorption capacity for various pollutants, indicating the versatility and potential of the material for water treatment.

Microplastic pollution has been deemed a serious environmental concern for many developing countries, including Vietnam. Thus, bioplastics produced from sustainable materials by microorganisms have been sourced as an alternative to mitigating microplastic pollution. This study conducted the screening of 47 strains of microalgae and cyanobacteria sourced from various locations and environmental conditions in Vietnam for the production of polyhydroxyalkanoates (PHAs) as a source of bioplastics. The experimental results demonstrate that 15 out of the total 47 screened microalgae and cyanobacteria strains could produce PHAs, and they exhibited diverse PHAs production despite being grown under the same incubation conditions. Furthermore, amongst these 15 strains, Arthrospira platensis NLHT3, Microcystis aeruginosa DTB1, Arthrospira platensis NLNA2, and Arthrospira platensis NBQN1 exhibited the highest PHAs accumulation rates of 4.18 %, 3.46 %, 3.01 %, and 2.82 % of cell dry weight, respectively. The analysis of polymer granules accumulated inside the cell biomass by transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) confirms that the accumulated biopolymers were PHAs.

Seafood processing wastewater contains many organic pollutants and nutrients that harm the environment if discharged without treatment. It is urgent to search for a solution to treat seafood processing wastewater for sustainable development purposes. This study aims to examine the different physico-chemical techniques used in seafood processing wastewater treatment, focusing on their ability to reduce pollutants with the aim of carbon neutrality. This study compares the effectiveness of coagulation-flocculation using Polyaluminium Chloride (PAC)/Anionic Polyacrylamide (APAM), chemical oxidation using Sodium hypochlorite (NaOCl), and adsorption using granular activated carbon (GAC). The results show that coagulation-flocculation with a PAC concentration of 125 mg/L after 30 minutes achieved a removal efficiency of 73.0 % for total suspended solids (TSS), 14.6 % for total dissolved solids (TDS), 65.0 % for chemical oxygen demand (COD), 50.0 % color, 10.0 % total nitrogen (TN), 1.0 % ammonium (NH₄⁺), and 10.0 % total phosphorus (TP). The addition of 62.5 mg/L APAM increased the removal efficiencies to 75.0 % TSS, 15.0 % TDS, 68.0 % COD, 50.3 % color, 10.1 % TN, 1.01 % NH₄⁺, and 10.5 % TP. pH 6.5 was ideal for the pollutant removal efficiencies in seafood processing wastewater using coagulation/flocculation. On the other hand, when using 500 mg/L of NaOCl in chemical oxidation for 15 minutes, it resulted in much lower pollutant removal efficiencies of 11.0 % TSS, 26.0 % COD, 50.0 % color, 6.80 % TN, 35.0 % NH₄⁺, while the TDS removal efficiency was not significant. Finally, using 20 g/L of GAC after 60 minutes recorded removal efficiencies of 75.0 % TSS, 18.0 % TDS, 56.8 % COD, 55.0 % color, 11.9 % TN, 20 % NH₄⁺, and 12.1 % TP. It was found that coagulation-flocculation was the most effective treatment method for seafood processing wastewater treatment when considering both the removal efficiency and cost benefit, at about 0.21 €/m³. These findings will help to develop efficient physico-chemical treatments for seafood processing wastewater with the aim of carbon neutrality.

Global warming have been serious problems worldwide. They have resulted in the saline intrusion reaching farther into the inland water system region, which negatively influences the aquatic environment and ecosystems. Our study assessed the tolerant capacity of a freshwater micro-alga, Scenedesmus protuberans, isolated from Vietnam to the salinity of 2 ‰, 4 ‰, and 8 ‰. We also evaluated the nitrate and phosphate uptake by the alga in different salinity of 0 ‰, 2 ‰, and 4 ‰. To address these two research questions, two experiments were conducted. The first experiment spanned 12 days and aimed to assess the salinity tolerance capacity of S. protuberans. The second experiment lasting for 20 days focused on investigating the nutrient (nitrate and phosphate) uptake by the alga under three different salinity levels. In the first experiment, we found that the S. protuberans could adapt and grow at the salinity up to 4 ‰ of incubation. In the second one, the micro-alga in the salinity of 0 ‰, 2 ‰, and 4 ‰ could uptake 88 %, 75 %, and 54 % of phosphate and remove 39 %, 56 %, and 36 % of nitrate from the water environment, respectively. Our results reveal a high potential for developing and validating the nutrient removal capacity of S. protuberans when applied to treat nutrients in polluted water, both in freshwater and brackish water systems, aligning with the net zero emission approach.

Jagakarsa is an urban area in South Jakarta, Indonesia, that uses groundwater for raw water because there are no clean water supply facilities. The significant increase in the need for clean water due to increasing urbanization threatens groundwater availability to maintain the balance of the surrounding environment. Natural conditions with a deep layer of clay and a dense built environment further increase runoff capacity because water has difficulty seeping into the soil. The intense extraction of groundwater without balancing groundwater recharge results in land subsidence. Until now, there has been no research on this issue. Thus, our research is necessary. This research aims to assess the potential of groundwater infiltration areas in Jagakarsa. Due to limited data, as a first step, we used a qualitative model with MCDM analysis (AHP and MIF methods) integrated with GIS to map potential groundwater recharge areas. The AHP method is explained in detail with a matrix system formula, readers can understand the calculation steps more easily. This study uses five influencing factors: geological formation, land use, slope, rainfall, and soil type. The results show that most study locations have low potential (AHP 74.49 % and MIF 75.25 %) for groundwater recharge. This groundwater recharge potential map was validated using groundwater level measurements. The accuracy of the AHP is 74.51 %, and the MIF method reaches 75.26 %. Therefore, further research is needed to obtain appropriate and effective technology for maintaining groundwater availability.

A new method utilizing sugarcane bagasse-derived ash (SB-dA) to remove and convert gold(III) to valuable noble gold metal has been developed. The SB-dA was purified with a mixed solution of 0.1 mol/L HCl and 0.3 mol/L HF, followed by 3 mol/L HNO₃, resulting in a silica-rich material with silanol (Si–OH) and siloxane (Si–O–Si) groups, along with an aromatic component. The gold(III) removal was endothermic (ΔH^o of 34.51 kJ/mol) and spontaneous (ΔG^o ranging from −27.72 to −29.81 kJ/mol as temperature increased from 30 to 50 °C). The activation energy (Ea) and standard entropy (ΔS^o) values were 35.15 and 0.2 kJ/mol, respectively, indicating increased interfacial irregularity during gold(III) removal. At an optimum pH of 4.2, the removal followed the Langmuir isotherm and the second-order kinetics models. The rate constant (k₂) enhanced from 3.32 to 7.56 × 10² L/mol·min, and Langmuir's removal capacity (b) rose from 0.18 to 0.25 × 10⁻⁴ mol/g as temperature increased from 30 to 50 °C. Silanol and siloxane groups played crucial role in gold(III) removal through adsorption, with silanol also active in reducing gold(III) to gold metal, a process that intensified by increasing temperatures.

Natural deep eutectic solvent (NADES) composed of choline chloride and formic acid was used to fractionate date waste into lignin and cellulose streams. NADES treatment increased the cellulose content from 44 wt% in raw waste (RW) to 72 wt% in extracted cellulose fibers (CFs). Scanning electron microscopy revealed needle-like fibers, underlining the effectiveness of NADES treatment in removing non-cellulosic components. Additionally, the CFs exhibited improved thermal stability, with an initial decomposition temperature ($T_{onset}$) of 265 °C. Kinetic analysis revealed a higher activation energy ($E_a$) of 100.90 kJ/mol for CFs than 63.10 kJ/mol for RW, indicating higher thermal stability due to enhanced cellulose content. Pyrolysis coupled with gas chromatography/mass spectroscopy analyses of CFs showed a lower release of nitrogen compounds and a higher content of hydrocarbons and cyclic ethers, all of which are beneficial for bio-oil production. Overall, the findings of this study will promote the use of NADES as an inexpensive, nontoxic, and recyclable solvent to advance the field of selective pyrolysis.