Anthropogenic CO₂ emission is identified as the major cause of climate change. The use of fossil fuels has to be accommodated, possibly with a CO₂ capture process. Sequestration of captured CO₂ at high pressure is proposed as a feasible option for future mitigation of climate change, though using fossil fuels. However, this needs significant energy input and carries the potential threat of a possible future catastrophe. Capture of CO₂ with possible recycling is a long-term sustainable option. In this paper, a process involving a chain of reactions using solid sodium to capture both CO₂ and SO₂ from a flue gas is described. A significantly detailed description of both chemical reactions and physical processes is discussed. Recycling of captured CO₂ and SO₂ in the form of solid graphite and elemental sulphur (as the by-products) is the special feature of this process. However, critical selection of intermediate process liquids and equipment in this process needs further study for real-life implementation of this scheme.

Studying the toxic risk of pesticide exposure to ladybird beetles is important from an agronomical and ecological perspective since larval and adult ladybirds are dominant predators of herbivorous pest insects (e.g., aphids) in various crops in China. This article mainly deals with the long-term effects of a single application of the insect growth regulator hexaflumuron on Coccinella septempunctata. A 72- h and a 33-day toxicity test with hexaflumuron (single application) were performed, starting with the second instar larvae of C. septempunctata. Exposure doses in the long-term experiment were based on the estimated 72-h acute LR50 (application rate causing 50 % mortality) value of 304 g active ingredient (a.i.) ha-1 for second instar larvae of C. septempunctata. The long-term test used five hexaflumuron doses as treatment levels (1/50, 1/100, 1/200, 1/400, and 1/800 of the 72-h acute LR50), as well as a solvent control and blank control treatment. The measurement endpoints used to calculate no observed effect application rates (NOERs) included development time, hatching, pupation, adult emergence, survival, and number of eggs produced. Analyzing the experimental data with one-way analysis of variance showed that the single hexaflumuron application had significant effects on C. septempunctata endpoints in the 33-day test, including effects on development duration (NOER 1.52 g a.i. ha-1), hatching (NOER 3.04 g a.i. ha-1), pupation (NOER 3.04 g a.i. ha-1), and survival (NOER 1.52 g a.i. ha-1). These NOERs are lower than the reported maximum field application rate of hexaflumuron (135 g a.i. ha-1) in cotton cultivation, suggesting potential risks to beneficial arthropods.

Effects of the combined application of ferrihydrite-modified diatomite (FHMD) and gypsum on phosphorus control were investigated in a laboratory-scale artificial aquarium under anoxic and agitation conditions over 120 days. Daily oscillation of a metal grid to simulate agitating effects by wind did not yield the sediment resuspension in the 120-day treatment aquarium (120-day aquarium) due to the gypsum stabilization, while significant sediment resuspension was observed in the control aquarium. The combined application of FHMD and gypsum did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. Under anoxic conditions and sediment resuspension conditions, a large increase in total phosphorus (TP) concentrations was observed in the control aquarium. However, the TP concentrations in the 120-day aquarium stayed relatively stable, within a range of 9.1–13.3 μg/L. After the 120 days’ incubation, translocation from mobile labile-P and organic-P to P adsorbed by FHMD occurred. The combined application of FHMD and gypsum effectively maintained TP levels within the oligotrophic range under anoxic and agitation conditions in the laboratory-scale artificial aquarium by removing phosphorus from lake water and reducing sedimentary phosphorus release via gypsum sediment stabilization and FHMD phosphorus immobilization.

This study was undertaken to synthesise a novel biomass-based chemically activated carbon from Australian pine cone and to investigate its effectiveness in the removal of anionic dye Congo red from aqueous solution. The effect of activation parameters such as the concentration of phosphoric acid and temperature were identified as the most efficient parameters for activation in the Congo red removal. The synthesised activated carbon was characterised by Fourier transform infrared and different physical properties, such as bulk density, CHNS analysis, carbon yield, particle size, zeta potential and Brunauer–Emmett–Teller surface area were also determined. Batch adsorption study showed that the amount of adsorption depends on various physico-chemical process parameters, such as solution pH, dye concentration, temperature and adsorbent dose. It was observed that Langmuir maximum adsorption capacity was 500 mg/g at a pH of 3.5. Furthermore, pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were fitted to examine the adsorption kinetic and mechanism of adsorption. Equilibrium data were fitted with Langmuir, Freundlich and Tempkin adsorption isotherm models. Thermodynamic parameters such as ΔG⁰, ΔH⁰, and ΔS⁰were also calculated. Finally, a single-stage batch adsorber design for the Congo red adsorption onto activated carbon particles was presented based on the Freundlich isotherm model equation. These results indicated pine cone biomass is a good and cheap precursor for the production of an effective activated carbon adsorbent and alternative to commercial-activated carbon.

This paper reports on the effect of activating agents such as the impregnation ratio of phosphoric acid (1:1–1:5) at constant activation temperature on the performance of porous activated carbon from waste residues (maize tassel). The variation in the impregnation ratio of the produced activated carbon (AC) from 1:1 to 1:5 enabled the preparation of a high surface area (1,263 m²/g) and a large pore volume (1.592 cm³/g) of AC produced from maize tassel (MT) using a convectional chemical activating agent (phosphoric acid). Impregnation ratios (IR) of the precursors were varied between 1:1 and 1:5 in which it was found that the ratio of 1:4 was optimal based on the high surface area, while 1:5 has the optimal pore volume value for the produced activated carbon.

Corn cob silica (CCS), produced via a modification of the sol-gel method, can reduce heavy metal availability and stabilize contaminated soil on abandoned mining sites. Adding 5 % (w/w) CCS to mining site soil increased pH from 4.0 to 7.7, and cation exchange capacity increased from 94.5 to 100.3 cmol+/kg. Sequential extraction showed that adding CCS decreased heavy metal availability in the soil. Mobility factor (MF) values indicated that CCS reduced Pb mobility more than that of Zn or Cu in all fractions. Pb concentrations in leachate from all fractions using the toxicity characteristic leaching procedure (TCLP) were greatly decreased by adding 3 % (w/w) CCS. CCS similarly reduced Zn concentrations in TCLP leachate. CCS addition did not impact Cu concentrations in leachate, likely because concentrations were much lower than those of the other metals. As was generally less mobile than the heavy metals; however, As mobility and leachability tended to increase with CCS addition because its oxyanions arsenite and arsenate have low affinity for negatively charged surfaces on the CCS. Shoot and root growth of Spinacia oleracea L. (spinach) was much greater in CCS-treated soil than in unamended soil. Results demonstrate the utility of CCS to stabilize heavy metals in contaminated mining site soil, but this treatment may not be ideal for As-contaminated soils.

In order to determine human exposure to the indoor toxicant, selection of dust fraction and understanding dust particle size distribution in settled indoor dust are very important. This study examined the influence of dust particle size on the concentration of polybrominated diphenyl ethers (PBDEs) congeners, assessed the distribution of dust particle size and characterized the main indoor emission sources of PBDEs. Accordingly, the concentrations of PBDE congeners determined in different indoor dust fractions were found to be relatively higher in the order of dust particle size: 45–106 μm > (<45 μm) > 106–150 μm. The finding shows arbitrary selection of dust fractions for exposure determination may result in wrong conclusions. Statistically significant moderate correlation between the concentration of Σ₉PBDEs and organic matter content calculated with respect to the total dust mass was also observed (r = 0.55, p = 0.001). On average, of total dust particle size <250 μm, 93.4 % (m/m%) of dust fractions was associated with less than 150 μm. Furthermore, of skin adherent dust fractions considered (<150 μm), 86 % (v/v%) is in the range of particle size 9.25–104.7 μm. Electronic materials treated with PBDEs were found the main emission sources of PBDE congeners in indoor environment. Based on concentrations of PBDEs determined and mass of indoor dust observed, 150 μm metallic sieve is adequate for human exposure risk assessment. However, research in this area is very limited and more research is required to generalize the fact.

The culture of Trametes gibbosa sp. white-rot fungi (WRF) 3 under mesophilic conditions can lead to the degradation of azo dye compounds. This ability of T. gibbosa sp. WRF 3 is attributed to the released enzymes that are able to catalyze the structural degradation of the azo dye compound. The effect of environmental factors such as carbon sources, nitrogen sources, and pH of growth medium were investigated in this research. The addition of 20 g/L glucose (carbon source) and yeast extract (nitrogen source) at pH 5 of growth medium enhanced the decolorization of Reactive Black 5 (RB5) dye up to 87.07 % within 30 days of incubation. The decolorization of RB5 can be analyzed using UV–vis spectroscopy and differential pulse cathodic stripping voltammetry (DPCSV). The maximum absorbance of RB5 was at 597 nm and decreased after the dye was treated with T. gibbosa sp. WRF 3. In the voltammetric analysis, we examined the effect of pH of Britton–Robinson buffer (BRB) medium on the detection of bis-azo compound of RB5. A stock solution of RB5 was used in the study, and it showed two reduction peak potentials at −0.5 and −0.7 V which attributed to the bis-azo bond, whereas the metabolic product showed one reduction peak at −0.6 V. The GC-MS mass spectrum confirmed the formation of metabolites at tR4.63 min and m/z of 73 after 30 days of incubation which was sec-butylamine.

The study aimed to investigate the biodegradation of contaminated soil with biodiesel, diesel, and petroleum by autochthonous soil microorganisms and also enriched with Bacillus subtilis by means of colorimetric method. The phytotoxicity was evaluated in recently contaminated soil and after 240 days to ensure the decrease of toxicity. The biodegradation assessment was carried out with redox 2,6-dichlorophenol indophenol (DCPIP) indicator and by the extraction of the contaminant in the soil with hexane. The amount of contaminant extracted from recently contaminated soil was compared to the amount found on the buried samples for 240 days. The phytotoxicity rates were evaluated by the use of Lactuca sativa seeds. Values of root and hypocotyl elongation were subjected to analysis of variance using the Kruskal-Wallis test. The results revealed that the autochthonous microorganisms were active on recently contaminated soil with biodiesel, because all biodiesel was biodegraded. Hence, only 0.001 g of biodiesel was extracted, and the phytotoxicity decreased after 240 days. On the other hand, the contaminated soil with diesel and petroleum was little active in 2,6-DCPIP test, and consequently, there was a large contaminant amount in soil after 240 days. Furthermore, petroleum and diesel were phytotoxic after biodegradation. The complex composition of the petroleum and diesel requires interactions of the microbial community able to biodegrade hydrocarbons and also metabolites from biodegradation. The naturally present microorganisms in the soil were capable of degrading the pollutant as much as the samples enriched with B. subtilis. The 2,6-DCPIP test is a simple and inexpensive methodology to analyze the potential biodegradation of all microorganisms of the soil and if the inoculation of the biodegrading microorganisms it will be necessary. Therefore, it would be helpful in bioremediation strategies.

Different cases of bioremediation technique were experimentally investigated here for decontaminating light non-aqueous phase liquid (LNAPL)-polluted groundwater collected from Panipat oil refinery situated in Haryana, India. Natural biodegradation of toluene, the selected LNAPL, was studied first under different varying substrate concentrations at room temperature (21.6 ± 0.3 °C). Biostimulation was then studied by mixing the polluted groundwater with a primary treated domestic wastewater for providing nutrients and other supplementary components to the native microbial population. For studying the remaining cases, small-scale wetland having plants of Canna generalis was developed in the laboratory with and without the presence of toluene in the rhizosphere. The wetland system in the presence of toluene was used here for developing the pre-grown microbial cultures to enhance the degradation rate of the LNAPL (bioaugmentation). The plant-assisted biostimulation was studied in the third case by adding the polluted groundwater with the root zone water of the wetland system developed without the presence of toluene. In the fourth case, the biostimulation was coupled with the bioaugmentation strategy by mixing the groundwater with the root zone water of the wetland system developed in the presence of toluene. A comparative account of these four different bioremediation techniques was prepared for their respective rates of biodegradation, duration of lag phases, and the total time of degradation. It was observed that the plant-assisted bioremediation techniques had better performance over the natural biodegradation and biostimulation methods of the considered LNAPL. The plant-assisted biostimulation coupled with the bioaugmentation technique needed almost no acclimatization time and accelerated the rate of degradation almost twofold compared to the natural bioremediation and, hence, is proved to be the best one among the other bioremediation techniques for decontaminating the LNAPL-polluted groundwater. The results of the conducted experiments can be used to obtain vital information on framing the engineered bioremediation planning for LNAPL-contaminated sites.