This study deals with the removal of chromium species from aqueous dilute solutions using polymer-enhanced ultrafiltration (PEUF) process. Three water soluble polymers, namely chitosan, polyethyleneimine (PEI) and pectin were selected for this study. The ultrafiltration studies were carried out using a laboratory scale ultrafiltration system equipped with 500,000 MWCO polysulfone hollow fiber membrane. The effects of pH and polymer composition on rejection coefficient and permeate flux at constant pressure have been investigated. For Cr(III), high rejections approaching 100% were obtained at pH higher than 7 for the three tested polymers. With chitosan and pectin, Cr(VI) retention showed a slight increase with solution pH and did not exceed a value of 50%. An interesting result was obtained with PEI. The retention of Cr(VI) approached 100% at low pH and decreased when the pH was increased. This behavior is opposite to what one can expect in the polymer-enhanced ultrafiltration of heavy metals. Furthermore, the concentration of polymer was found to have little effect on rejection. Permeate flux remained almost constant around 25% of pure water flux.
This review examines strategies to enhance the mechanical properties of chitosan/polyvinyl alcohol (PVA) electrospun nanofibers, recognized for their biomedical and industrial applications. It begins by outlining the fundamental properties of chitosan and PVA, highlighting their compatibility and mechanical characteristics. The electrospinning process is discussed, focusing on how various parameters and post-treatment methods influence fiber formation and performance. Key strategies for improvement are analyzed, including material modifications through blending and structural modifications like fiber orientation and multilayer constructions, and surface modifications such as coating and functionalization. The review also covers advanced characterization methods to evaluate mechanical properties and provides a comparative analysis of different enhancement approaches. Applications in biomedical and industrial contexts are explored, showcasing the versatility and innovation potential of these nanofibers. Finally, current challenges are addressed, and future research directions are proposed to overcome these obstacles and further enhance the mechanical properties of chitosan/PVA electrospun nanofibers, guiding their development for practical applications.
This study investigates the potential of Escherichia coli and Aeromonas hydrophila as bioremediation agents for removing copper (Cu) and zinc (Zn) from contaminated water. Although Cu and Zn are necessary in trace levels, excessive amounts can be harmful and can linger in aquatic environments, endangering the food chain. Bioremediation using microorganisms offers an alternative method for mitigating heavy metal pollution. In this study, 126 tilapia fish (Oreochromis mossambicus) were exposed to CuSO4 and ZnCl2 for 15 days, followed by treatment with E. coli and A. hydrophila. Atomic absorption spectrometry (AAS) revealed that both bacterial treatments reduced copper and zinc accumulation in fish organs, though they did not fully heal external lesions. Histopathological analysis showed significant reductions in melanomacrophage centers (MMC), cell necrosis, cell dissociation, and vacuolization in fish liver tissue after bacterial treatment, particularly at concentrations of 2.5 mg.L-1 and 5 mg.L-1 for CuSO4 and 7.5 mg.L-1 for ZnCl2. These findings suggest that E. coli and A. hydrophila have the potential to be developed as effective bioremediation agents for CuSO4 and ZnCl2 pollution in aquatic environments.
The residual activity of herbicides may be detrimental to the environment, requiring analysis of the persistent residues in the soil and water. A field study was conducted to measure the residues of Imidazolinone (IMI) in three Clearfield® rice field soils at three different locations in Malaysia. The analyses of IMI in the soil samples were carried out using a high-performance liquid chromatography (HPLC). These herbicides are widely used; however, few studies have been conducted on both residues, especially in the context of Malaysian soil. Residues of imazapic and imazapyr were found to fall within 0.03-0.58 µg/mL and 0.03-1.96 µg/mL, respectively, in three locations. IMI herbicides are persistent in the soil, and their residues remain for up to 85 days after application. A pre-harvest study was suggested for these herbicides on water, which will provide a clearer indicator on the use of IMI in Clearfield® rice fields.
This study concerns the role of activated carbon (AC) from palm raceme as a support material for the enhancement of lipase-catalyzed reactions in an aqueous solution, with deep eutectic solvent (DES) as a co-solvent. The effects of carbonization temperature, impregnation ratio, and carbonization time on lipase activity were studied. The activities of Amano lipase from Burkholderia cepacia (AML) and lipase from the porcine pancreas (PPL) were used to investigate the optimum conditions for AC preparation. The results showed that AC has more interaction with PPL and effectively provides greater enzymatic activity compared with AML. The optimum treatment conditions of AC samples that yield the highest enzymatic activity were 0.5 (NaOH (g)/palm raceme (g)), 150 min, and a carbonization temperature of 400 °C. DES was prepared from alanine/sodium hydroxide and used with AC for the further enhancement of enzymatic activity. Kinetic studies demonstrated that the activity of PPL was enhanced with the immobilization of AC in a DES medium.