Adsorption-Desorption Profile of Methylene Blue Dye on Raw and Acid Activated Kaolinite

The efficiencies of raw (RK) and acid activated (0.5 M AAK) kaolinite clay minerals to remove methylene blue (MB) dyes in aqueous solution were investigated and compared. The 0.5 M AAK was prepared by treatment of RK in dilute 0.5 M HCl aqueous solution under reflux. Kaolinite adsorbents were characterized and their MB removal performances were evaluated via the batch method. MB desorption from spent kaolinites was investigated at pH 4 to 8. The MB removal was increased with increasing initial dye concentration, agitation speed and adsorbent dosage in 60 min reaction time at pH 6. Both kaolinites showed high MB removal (up to 97%). The Freundlich model has the best-fit equilibrium adsorption isotherm model for RK and 0.5 M AAK. The kinetic data for both adsorbents showed strong agreement with the pseudo second order kinetic model (r2 > 0.98). Nevertheless, the spent RK adsorbent demonstrated a significant higher MB retention than 0.5 M AAK in desorption experiments. Kaolinite clays have great potential as cost-effective materials for dyes removal in wastewater treatment

Antioxidant and antimicrobial activity of cuttlebone chitosan against Escherichia coli, Staphylococcus aureus and Candida albicans

The discovery of new antibiotics for infectious diseases has become challenging due to the rise of antimicrobial resistance. Meanwhile, chitosan has been considerably used in many branches of research. It has been discovered to have some good benefits in medicals, pharmaceuticals, and food technologies. In this study, chitosan was prepared from the cuttlebone of Sepia sp. by chemical method and analyzed by using FT-IR spectrophotometer for the confirmed presence of its functional groups. There are three types of reactive functional groups in the chitosan which are the amino group and primary and secondary hydroxyl group attached to the C-2, C-3, and C-6 positions respectively. Chitosan has a high cationic property due to the presence of its amino group. The bacteriostatic activity of chitosan occurs due to its positive charge in acidic concentration that interacts with the negatively charged residue of carbohydrates, lipids, and proteins located on the cell surface of bacteria. The antioxidant activity was conducted using DPPH radical scavenging assay with a chitosan concentration ranging from 0.1 to 10 mg/mL and a hydrogen peroxide scavenging assay with a chitosan concentration ranging from 0.1 to 1.6 mg/mL. The antimicrobial activity of chitosan from cuttlebone was analyzed against two different bacterial strains (Escherichia coli & Staphylococcus aureus) and a fungal strain, Candida albicans by disc diffusion and minimum inhibitory concentration (MIC) method. The results show that through the DPPH radical assay, the scavenging activity was 59.7% at the concentration of chitosan at 10mg/mL, while through the hydrogen peroxide assay the scavenging activity was 56% at the concentration of chitosan at 1.6 mg/mL. Besides, this chitosan from Sepia sp. has concentration-dependent antimicrobial activity with higher antifungal activity compared to antibacterial activity against all tested organisms and may become a potential agent for antibiotic discovery

Antioxidant and antimicrobial activity of cuttlebone chitosan against Escherichia coli, Staphylococcus aureus and Candida albicans

The discovery of new antibiotics for infectious diseases has become challenging due to the rise of antimicrobial resistance. Meanwhile, chitosan has been considerably used in many branches of research. It has been discovered to have some good benefits in medicals, pharmaceuticals, and food technologies. In this study, chitosan was prepared from the cuttlebone of Sepia sp. by chemical method and analyzed by using FT-IR spectrophotometer for the confirmed presence of its functional groups. There are three types of reactive functional groups in the chitosan which are the amino group and primary and secondary hydroxyl group attached to the C-2, C-3, and C-6 positions respectively. Chitosan has a high cationic property due to the presence of its amino group. The bacteriostatic activity of chitosan occurs due to its positive charge in acidic concentration that interacts with the negatively charged residue of carbohydrates, lipids, and proteins located on the cell surface of bacteria. The antioxidant activity was conducted using DPPH radical scavenging assay with a chitosan concentration ranging from 0.1 to 10 mg/mL and a hydrogen peroxide scavenging assay with a chitosan concentration ranging from 0.1 to 1.6 mg/mL. The antimicrobial activity of chitosan from cuttlebone was analyzed against two different bacterial strains (Escherichia coli & Staphylococcus aureus) and a fungal strain, Candida albicans by disc diffusion and minimum inhibitory concentration (MIC) method. The results show that through the DPPH radical assay, the scavenging activity was 59.7% at the concentration of chitosan at 10mg/mL, while through the hydrogen peroxide assay the scavenging activity was 56% at the concentration of chitosan at 1.6 mg/mL. Besides, this chitosan from Sepia sp. has concentration-dependent antimicrobial activity with higher antifungal activity compared to antibacterial activity against all tested organisms and may become a potential agent for antibiotic discovery

Removal of lead from aqueous solution using superparamagnetic palygorskite nanocomposite: Material characterization and regeneration studies

A palygorskite-iron oxide nanocomposite (Pal-IO) was synthesized in situ by embedding magnetite into the palygorskite structure through co-precipitation method. The physico-chemical characteristics of Pal-IO and their pristine components were examined through various spectroscopic and micro-analytical techniques. Batch adsorption experiments were conducted to evaluate the performance of Pal-IO in removing Pb(II) from aqueous solution. The surface morphology, magnetic recyclability and adsorption efficiency of regenerated Pal-IO using desorbing agents HCl (Pal-IO-HCl) and ethylenediaminetetraacetic acid disodium salt (EDTA-Na2) (Pal-IO-EDTA) were compared. The nanocomposite showed a superparamagnetic property (magnetic susceptibility: 20.2 emu g−1) with higher specific surface area (99.8 m2 g−1) than the pristine palygorskite (49.4 m2 g−1) and iron oxide (72.6 m2 g−1). Pal-IO showed a maximum Pb(II) adsorption capacity of 26.6 mg g−1 (experimental condition: 5 g L−1 adsorbent loading, 150 agitations min−1, initial Pb(II) concentration from 20 to 500 mg L−1, at 25 °C) with easy separation of the spent adsorbent. The adsorption data best fitted to the Langmuir isotherm model (R2 = 0.9995) and pseudo-second order kinetic model (R2 = 0.9945). Pb(II) desorption using EDTA as the complexing agent produced no disaggregation of Pal-IO crystal bundles, and was able to preserve the composite's magnetic recyclability. Pal-IO-EDTA exhibited almost 64% removal capacity after three cycles of regeneration and preserved the nanocomposite's structural integrity and magnetic properties (15.6 emu g−1). The nanocomposite holds advantages as a sustainable material (easily separable and recyclable) for potential application in purifying heavy metal contaminated wastewaters

Production of lactic acid by immobilized lactic acid bacteria in modified chitosan beads

Lactic acid has been widely used in numerous applications, for example in food industry, pharmaceutical, cosmetics and production of biodegradable plastic. Worldwide production of lactic acid is mostly through the fermentation of lactic acid bacteria. However, during the food processing stages, the lactic acid bacteria face inhibition problems caused by contaminants. Therefore, immobilization of lactic acid bacteria by entrapment within polymer matrix was selected to minimize this problem. In this study, lactic acid bacteria were immobilized in chitosan which is a biopolymer derived from the deacetylation of chitin. The chitosan beads were prepared by dropping chitosan solution in sodium pyrophosphate. The effect of modifications of chitosan beads by adding polyvinyl alcohol (PVA) and crosslinking with glutaraldehyde (Glu) in strengthening the beads for the fermentation process were studied. Modification of beads with PVA and Glu to enhance their mechanical strength showed positive result. Comparing the different types of beads, the Chitosan-Glu beads were found to maintain its shapes after the second cycle of fermentation, but produced the lowest amount of lactic acid, which is 315 x 10-3 g /

Formation of chitosan beads and lactic acid production by chitosan-immobilised lactobacillus sp

Chitosan is a biopolymer derived by deacetylation of chitin and has special properties such as hydrophilicity, biocompatibility, and is biodegradable. In this study, chitin was obtained from Tiger prawn waste through fermentation process. The chitin was then deacetylated to form chitosan with various degrees of deacetylation. Chitosan beads were prepared by dropping chitosan solution into sodium pyrophosphate which act as gelling agent. Several parameters such as degree of deacetylation (DD), concentration of chitosan solution, pH and concentration of sodium pyrophosphate solution were studied to determine their effect towards the formation and porosity of chitosan beads. High DD, high concentration of chitosan, and high pH of sodium pyrophosphate were found important to facilitate the formation of spherical shaped chitosan beads which is also supported by SEM and IR analyses. The fermentation of glucose by chitosan-immobilised Lactobacillus sp. produced 535 x 10-3 g/L of lactic acid over a period of three days. Upon recycling, chitosan-immobilised cells were able to maintain its shape until the third cycle

Insight into Structural Features of Magnetic Kaolinite Nanocomposite and Its Potential for Methylene Blue Dye Removal from Aqueous Solution

An in-depth understanding on the structural features of engineered magnetic adsorbent is important for forecasting its efficiencies for environmental clean-up studies. A magnetic kaolinite nanocomposite (MKN) was prepared using Malaysia’s natural kaolinite via co-precipitation method with a three different clay: iron oxide mass ratio (MKN 1:1, MKN 2:1 and MKN 5:1). The morphology and structural features of the magnetic composites were systematically investigated using techniques, such as: Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), surface area analysis (BET), Vibrating Sample Magnetometer (VSM), and zeta potential measurement. The removal efficiencies of the adsorbent for Methylene Blue (MB) dye were studied in batch method as a function of pH and initial concentration. MKN1:1 demonstrated the highest magnetisation susceptibility (Ms) of 35.9 emu/g with four-fold-increase in specific surface area as compared to the pristine kaolinite. Preliminary experiment reveals that all MKNs showed almost 100% removal of MB at low initial concentration (<50 ppm). The spent MKN adsorbent demonstrated an easy recovery via external magnetic field separation and recorded maximum adsorption capacity of 18.1 mg/g. This research gives an insight on the surface characteristics of magnetic clay composite for potential application as an effective and low-cost adsorbent in treating dye contaminated water. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Bioremediation of PAHs and VOCs:Advances in clay mineral-microbial interaction

Bioremediation is an effective strategy for cleaning up organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). Advanced bioremediation implies that biotic agents are more efficient in degrading the contaminants completely. Bioremediation by microbial degradation is often employed and to make this process efficient, natural and cost-effective materials can serve as supportive matrices. Clay/modified clay minerals are effective adsorbents of PAHs/VOCs, and readily available substrate and habitat for microorganisms in the natural soil and sediment. However, the mechanism underpinning clay-mediated biodegradation of organic compounds is often unclear, and this requires critical investigation. This review describes the role of clay/modified clay minerals in hydrocarbon bioremediation through interaction with microbial agents in specific scenarios. The vision is on a faster, more efficient and cost-effective bioremediation technique using clay-based products. This review also proposes future research directions in the field of clay modulated microbial degradation of hydrocarbons

Mild acid and alkali treated clay minerals enhance bioremediation of polycyclic aromatic hydrocarbons in long-term contaminated soil:A 14C-tracer study

Bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils requires a higher microbial viability and an increased PAH bioavailability. The clay/modified clay-modulated bacterial degradation could deliver a more efficient removal of PAHs in soils depending on the bioavailability of the compounds. In this study, we modified clay minerals (smectite and palygorskite) with mild acid (HCl) and alkali (NaOH) treatments (0.5–3 M), which increased the surface area and pore volume of the products, and removed the impurities without collapsing the crystalline structure of clay minerals. In soil incubation studies, supplements with the clay products increased bacterial growth in the order: 0.5 M HCl ≥ unmodified ≥ 0.5 M NaOH ≥ 3 M NaOH ≥ 3 M HCl for smectite, and 0.5 M HCl ≥ 3 M NaOH ≥ 0.5 M NaOH ≥ 3 M HCl ≥ unmodified for palygorskite. A14C-tracing study showed that the mild acid/alkali-treated clay products increased the PAH biodegradation (5–8%) in the order of 0.5 M HCl ≥ unmodified > 3 M NaOH ≥ 0.5 M NaOH for smectite, and 0.5 M HCl > 0.5 M NaOH ≥ unmodified ≥ 3 M NaOH for palygorskite. The biodegradation was correlated (r = 0.81) with the bioavailable fraction of PAHs and microbial growth as affected particularly by the 0.5 M HCl and 0.5 M NaOH-treated clay minerals. These results could be pivotal in developing a clay-modulated bioremediation technology for cleaning up PAH-contaminated soils and sediments in the field

Structural evolution of chitosan-palygorskite composites and removal of aqueous lead by composite beads

This paper investigates the structural evolution of chitosan-palygorskite (CP) composites in relation to variable mass ratios of their individual components. The composite beads' performance in lead (Pb) adsorption from aqueous solution was also examined. The composite beads were prepared through direct dispersion of chitosan and palygorskite at 1:1, 1:2 and 2:1 mass ratios (CP1, CP2 and C2P, respectively). Analyses by Fourier transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the dependence of the composites' structural characteristics on their composition mass ratio. The chitosan-palygorskite composite beads exhibited a better Pb adsorption performance than the pristine materials (201.5, 154.5, 147.1, 27.7 and 9.3 mg g -1 for CP1, C2P, CP2, chitosan and palygorskite, respectively). Adsorption of Pb by CP1 and CP2 followed Freundlich isothermal model, while C2P fitted to Langmuir model. Kinetic studies showed that adsorption by all the composites fitted to the pseudo-second order model with pore diffusion also acting as a major rate governing step. The surface properties and specific interaction between chitosan and palygorskite in the composites were the most critical factors that influenced their capabilities in removing toxic metals from water