Effect of Titanium, Silver and Zinc Nanoparticles on Microalgae in the Aquatic Environment

Metallic nanoparticles (MNPs) are commonly incorporated in products found in households, industries, and agriculture. The presence of MNPs in the aquatic environment causes damage to living organisms and pollutes the water body rendering it harmful for human consumption. Several studies have been made on the toxicity of MNPs toward microalgae. Most of these studies reported changes in the cellular structure, growth rate, pigments, proteins, and enzymatic activity of microalgae. This review paper focuses on the toxic effects of titanium, zinc, and silver nanoparticles on microalgae in the aquatic environment. A better understanding of the behavior of MNPs in the ecosystem will allow scientists to produce environmentally safe MNPs

Study of Chlorella vulgaris from Different Growth Phases as Biosensor for Detection of Titanium and Silver Nanoparticles in Water

The increased use of metallic nanoparticles has led to concern for environmental contamination and disruption in water quality. Therefore, effective screening of metallic nanoparticles is important for detecting metallic nanoparticles in aquatic environments. Biosensors offer several advantages, including high sensitivity to pollutants, short response time, energy efficiency, and low waste generation. In this study, a whole-cell biosensor was developed using microalga Chlorella vulgaris as a recognition element, and its fluorescence response was used as a measuring parameter for detecting the presence of titanium dioxide (TiO2) and silver (Ag) nanoparticles in water. The responses of C. vulgaris at the lag, exponential, and stationary phases to different concentrations of TiO2 and Ag nanoparticles were studied. The results showed that in TiO2 and Ag nanoparticles exposures, the highest fluorescence change (50-150%) was observed at the lag phase, whereas the lowest fluorescence change (40-75%) was observed at the stationary phase. A significant fluorescence change was observed in 15 min. The immobilized C. vulgaris under TiO2 and Ag nanoparticles exposures showed 30-180% higher fluorescence change than the negative control, indicating the potential of C. vulgaris as a biosensor for rapid detection of TiO2 and Ag nanoparticles in water. The mathematical modeling of the responses of C. vulgaris to TiO2 and Ag nanoparticles at 15 min of exposure with high R2 indicated that this biosensor is sensitive to the concentration tested (0.010–10.000 mg.L-1). Taken together, these results reveal that, for the first time, it is possible to detect TiO2 and Ag nanoparticles in water within a very short time using a microalgae-based biosensor. Moreover, no genetic engineering requirement makes this biosensor simple, economical, and free from the restriction on genetically modified microorganisms for environmental applications

Hydrogen sulfide (H2S) conversion to hydrogen (H2) and value-added chemicals : Progress, challenges and outlook

Hydrogen sulfide (H2S) is a toxic gas released from natural occurrences (such as volcanoes, hot springs, municipal waste decomposition) and human economic activities (such as natural gas treatment and biogas production). Even at very low concentrations, H2S can cause adverse health impacts and fatality. As such, the containment and proper management of H2S is of paramount importance. The recovered H2S can then be transformed into hydrogen (H2) and various value-added products as a major step towards sustainability and circular economy. In this review, the state-of-the-art technologies for H2S conversion and utilization are reviewed and discussed. Claus process is an industrially established and matured technology used in converting H2S to sulfur and sulfuric acid. However, the process is energy intensive and emits CO2 and SO2. This calls for more sustainable and energy-efficient H2S conversion technologies. In particular, recent technologies for H2S conversion via thermal, biological, plasma (thermal and non-thermal), electrochemical and photocatalytic routes, are critically reviewed with respect to their strengths and limitations. Besides, the potential of diversified value-added products derived from H2S, such as H2, syngas, carbon disulfide (CS2), ammonium sulphate ((NH4)2SO4), ammonium thiosulfate ((NH4)2S2O3), methyl mercaptan (CH3SH) and ethylene (C2H4) are elucidated in detail with respect to the technology readiness level, market demand of products, technical requirements and environmental impacts. Lastly, the technological gaps and way forward for each technology are also outlined

Penentuan kapasiti dan jenis pencerapan zeolit asli terhadap bahan pencelup sintetik

Zeolite, which is recognised as a molecular sieve, has fine pore size and high surface area has been used as an adsorbent to adsorb synthetic basic dye from coloured wastewater. Natural mordenite zeolite originated from Indonesia was modified to its base form and its adsorption capacity towards synthetic basic yellow 11 was determined. The type of adsorption of the zeolite sample towards synthetic basic dye was determine by four methods, name by the affect of calcination of zeolite sample on the adsorption capacity, regeneration of the zeolite sample, determination of the changes of structural characteristics and determination of the changes of cation property. This study shows that the zeolite sample has very high adsorption capacity toward synthetic base dye. Calcination of the zeolite sample and thermal regeneration result in a decreased of the adsorption capacity. The unchanged of structural characteristics and natrium ion exchange in zeolite sample after adsorption and regeneration indicate that the type of adsorption in the adsorption process of zeolite sample towards synthetic dye were a mixture of chemisorption and physisorption

Microalgal Growth and Nutrient Removal Efficiency in Non-Sterilised Primary Domestic Wastewater

Microalgae biomass can produce high quantities of biochemicals that can be used in various applications such as biodiesel, biogas, and aquaculture feed. The potential of sterilizing wastewater for microalgae-based wastewater treatment on a lab scale is well introduced. However, the operation cost for large-scale microalgae cultivation in wastewater treatment plants is high if using sterilising wastewater as the growth medium. The present study aimed to evaluate the growth of Scenedesmus sp., Chlorococcum aquaticum, Ankistrodesmus augustus, and Haematococcus pluvialis in non-sterilised domestic wastewater and their potential for pollutant removal in wastewater. The microalgae were cultivated in different concentrations of non-sterilised domestic wastewater, collected from a primary wastewater plant of a national sewerage company in Malaysia. Each species’ capacity for growth and the removal of pollutants were assessed. The results showed that the cell density, maximum biomass productivity, and biomass concentration of H. pluvialis, Scenedesmus sp., and C. aquaticum in 100% wastewater were significantly higher than the standard medium. Higher biomass concentration was obtained from H. pluvialis and C. aquaticum in 100% wastewater (815 g/L and 775.83 mg/L); nevertheless, Scenedesmus sp. in 100% wastewater yielded the highest specific growth rate (0.798 d−1) and the maximum biomass productivity (99.33 mg/L/day). Scenedesmus sp. in 100% wastewater also achieved better removal efficiency of total nitrogen (TN), total phosphorus (TP), and ammonia (N-NH4) with more than 90%. All tested microalgae species successfully remove nitrogen, ammonium, and phosphorus and reach the concentration limits set by the Department of the Environment, Malaysia. This study demonstrated that microalgae can grow well in non-sterilised domestic wastewater while simultaneously removing nitrogen and phosphorus effectively

The Responses of Carotenoids in Anabaena cylindrica to Single and Combined Metals of Nickel, Aluminum and Lithium

In the real polluted environment, the metals usually do not present in single pure form, but occur in mixture. Cyanobacteria are the most commonly available aquatic organisms in these environment, thus, there is a need to study the responses of carotenoids, a kind of antioxidant in cyanobacteria towards combined heavy and light metals. In this paper, Anabaena cylindrica was immobilized using agarose and exposed to the different concentration of single and combined Ni, Al and Li for 2 hours. The responses of carotenoids were determined using spectrophotometer at λ = 450 nm. The result showed that immobilized A. cylindrica responded differently to the exposure of single and combined metals. The cells were sensitive to single and combined Ni, Al and Li within the detection range of 0.001 mg/L to 10.000 mg/L. The value of R 2 indicated the immobilized A. cylindrica responded in correlation to the concentration of the metals. Thus, A. cylindrica has the potential to be used as bioindicator for detection of single and combined metals