Studies on the removal of nickel from aqueous solutions using modified riverbed sand

This paper highlights the utility of riverbed sand (RS) for the treatment of Ni(II) from aqueous solutions. For enhancement of removal efficiency, RS was modified by simple methods. Raw and modified sands were characterized by scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR) to investigate the effect of modifying the surface of RS. For optimization of various important process parameters, batch mode experiments were conducted by choosing specific parameters such as pH (4.0–8.0), adsorbent dose (1.0–2.0 g), and metal ion concentrations (5–15 mg/L). Removal efficiency decreased from 68.76 to 54.09 % by increasing the concentration of Ni(II) in solution from 5 to 15 mg/L. Removal was found to be highly dependent on pH of aqueous solutions and maximum removal was achieved at pH 8.0. The process of removal follows first-order kinetics, and the value of rate constant was found to be 0.048 min^?1 at 5 mg/L and 25 °C. Value of intraparticle diffusion rate constant (k _id) was found to be 0.021 mg/g min^1/2 at 25 °C. Removal of Ni(II) decreased by increasing temperature which confirms exothermic nature of this system. For equilibrium studies, adsorption data was analyzed by Freundlich and Langmuir models. Thermodynamic studies for the present process were performed by determining the values of ΔG°, ΔH°, and ΔS°. Negative value of ?H° further confirms the exothermic nature of the removal process. The results of the present investigation indicate that modified riverbed sand (MRS) has high potential for the removal of Ni(II) from aqueous solutions, and resultant data can serve as baseline data for designing treatment plants at industrial scale.     

Towards the Prediction of Heat and Mass Transfer in an Air-Conditioned Environment for a Life Support System in Space

Long-term flights or the establishment of permanent bases in space provide serious challenges for life support systems. Plants are essential companion life forms for such space missions, where human habitats must mimic the cycles of life on earth to generate and recycle food, oxygen and water. Nowadays, the chemical–mechanical recycling systems used in the international space station are much more compact, less labour intensive and more reliable than plant-based systems, but these systems would be too expensive for the long-term human exploration. In order to improve living conditions for humans and plants, we need an accurate characterisation of the mass transfer phenomena related to condensation of humid air. We are interested in developing an experimental protocol, which would help us to establish a theoretical model describing the heterogeneous transfers along a wall or a plant in an air-conditioned environment. Initially, we started in dry conditions by measuring the velocity profiles within the boundary layer that develop on a horizontal or a vertical flat plate in a wind tunnel. The velocity ranged from 0.5 to 2.5 m s^?1. Existing coupled heat and mass transfer measurement results relevant to our applications are discussed.     

Dietary Spirulina platensis alleviates aluminum and aluminum fluoride induced histopathological and biochemical alterations in mice kidney

Aluminum and its salts widely used in our daily life have been reported nephrotoxic to humans and animals following prolonged exposure. Therefore, the present study was made to examine the renoprotective role of Spirulina platensis against Al³⁺ and AlF₃ in male Swiss albino mice. Exposure to these chemicals decreased feed and water intake, and body and kidney weights. Histology of kidney and their biochemistry were also markedly altered along with that of serum biochemistry. Spirulina not only minimize toxic effects of test chemicals but also favored faster recovery of treated mice after their withdrawal.     

Toxic effect of stem bark and leaf of Euphorbia hirta plant against freshwater vector snail Lymnaea acuminata

The aqueous stem bark and leaf extracts of plant Euphorbia hirta (family-Euphorbiaceae) have potent molluscicidal activity. Sub-lethal doses (40% and 80% of LC50) of aqueous stem bark and leaf extracts of this plant also significantly (P<0.05) alter the levels of total protein, total free amino acid, nucleic acids (DNA and RNA) and the activity of enzyme protease and acid and alkaline phosphatase in various tissues of the vector snail Lymnaea acuminata in time and dose dependent manner. Euphorbia hirta (family-Euphorbiaceae) commonly known as Dudhi, is a common medicinal plant of India, which is used in variety of diseases i.e. cough, asthma, colic, dysentery, genito urinary diseases.     

Arsenic contamination of the environment: a new perspective from central-east India

This paper reports a regional contamination of the environment in central-east India that does not share geology or boundary with the Bengal Delta Plain. About 30,000 people residing in 30 villages and towns are directly exposed to arsenic and more than 200,000 people are "at risk." Complete geographical extent of this contamination is being established, and this newly reported contaminated area could be quite large. This paper further reports that the mechanisms involved in arsenic mobilisation are complex and the two theories of arsenic mobilisation, i.e., pyrite oxidation and oxyhydroxides reduction, do not fully explain the high levels of arsenic contamination. This paper also proposes the "oxidation-reduction theory" for arsenic mobilisation where the arsenic originates from the arsenopyrite oxidation and the arsenic thus mobilised forms the minerals and gets reduced underground in favourable Eh conditions. The stoppage of water withdrawal from the contaminated sources did not result in lowering of arsenic levels as expected according to the heavy groundwater extraction theory (pyrite oxidation theory). Cases of arsenicosis in the region are on the rise and the switchover to less contaminated water has not reversed the arsenicosis progression in the affected persons even after 2 years. Surface water of the rivers is also being contaminated because of the probable dislocation of contaminated groundwater due to the heavy rains in monsoon season, which indicates that the river water could be a major carrier of arsenic in dissolved or adsorbed forms that may be a cause of contamination of the delta plains.     

Exergy analysis of the transcritical N2O refrigeration cycle with a vortex tube

In this article, a comparative study is presented for the transcritical cycle with expansion valve (TCEV) and transcritical cycle with vortex tube (TCVT) mainly based on the second law of thermodynamics. Natural refrigerant nitrous oxide (N₂O) is used in both the cycles for analysis. The evaporator and gas cooler temperatures are varied from ?55°C to 5°C and 35°C to 60°C, respectively. The effects of various operating and design parameters on the optimum heat rejection pressure, coefficient of performance (COP), exergy loss (irreversibility), and the exergetic efficiency are studied. Exergy analysis of each component in TCEV and TCVT is performed to identify the amount and locations of irreversibility. It is observed that the use of the vortex tube in place of the expansion valve reduces the total exergy losses and increases the exergetic efficiency as well as COP. The exergetic efficiency and COP of the TCVT are on average 10–12% higher compared to TCEV for the considered operating conditions. The computed values of the exergetic efficiency for TCVT using refrigerant N₂O are the highest at an evaporator temperature of ?55°C, and the corresponding values of exergetic efficiency and exergy losses varies between 25.35% and 15.67% and between 74.65% and 84.33%, respectively. However, COP at the same evaporator temperature of ?55°C varies between 0.83 and 0.51. Furthermore, the optimum heat rejection pressure in TCVT is lower compared to that in TCEV. The results offer significant help for the optimum design and operating conditions of TCVT with refrigerant N₂O.     

Forecasting daily maximum surface ozone concentrations in Brunei Darussalam--an ARIMA modeling approach

A time series approach using autoregressive integrated moving average (ARIMA) modeling has been used in this study to obtain maximum daily surface ozone (O3) concentration forecasts. The order of the fitted ARIMA model is found to be (1,0,1) for the surface O3 data collected at the airport in Brunei Darussalam during the period July 1998-March 1999. The model forecasts of one-day-ahead maximum O3 concentrations have been found to be reasonably close to the observed concentrations. The model performance has been evaluated on the basis of certain commonly used statistical measures. The overall model performance is found to be quite satisfactory as indicated by the values of Fractional Bias, Normalized Mean Square Error, and Mean Absolute Percentage Error as 0.025, 0.02, and 13.14% respectively.     

Passive air sampling of organochlorine pesticides in a northeastern state of India, Manipur

Thirty-six polyurethane foam disk passive air samplers (PUF-PAS) were deployed over a year during January to December, 2009 at three locations, i.e., Imphal (urban site), Thoubal (rural site) and Waithou (alpine site) of Manipur, to assess the seasonal local atmospheric emission of selected organochlorine pesticides (OCPs). The average concentration of HCHs monitored at mountain site during hot season (Mar, Apr, and May) and rainy seasons (Jun, Jul, Aug, and Sep) were 403 and 349 pg/m3, respectively. DDTs had a high concentration with 384 pg/m3 at rural site and 379 pg/m3 at urban site during hot seasons. Endosulfans and chlordane were found high in concentration during hot seasons (260 pg/m3) and low during retreating monsoon seasons (44 pg/m3) at rural site. Most of the OCPs concentrations were high during cultivation period. The OCP concentrations of rainy season were highly correlated (p < 0.01) with OCPs of hot seasons. Further, positive correlation (p < 0.05) was also obtained between cold seasons and retreating monsoon. Principal component analysis showed a significant correlation among the four seasons and distribution pattern of OCPs in air. Back trajectory analysis by using HYPSLIT model showed a long range air transport of OCPs to the present study area. Present OCP levels at Manipur is an outcome of both local emission and also movement of air mass by long range atmospheric transport.     

Assessment of persistent organic pollutants in soil and sediments from an urbanized flood plain area

Polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and phenolic compounds (PCs) are persistent organic compounds. Contamination of these potentially toxic organic pollutants in soils and sediments is most studied environmental compartments. In recent past, studies were carried out on PAHs, OCPs and PCs in various soils and sediments in India. But, this is the first study on these pollutants in soils and sediments from an urbanized river flood plain area in Delhi, India. During 2018, a total of fifty-four samples including twenty-seven each of soil and sediment were collected and analyzed for thirteen priority PAHs, four OCPs and six PCs. The detected concentration of ∑PAHs, ∑OCPs and ∑PCs in soils ranged between 473 and 1132, 13 and 41, and 639 and 2112 µg/kg, respectively, while their concentrations in sediments ranged between 1685 and 4010, 4.2 and 47, and 553 and 20,983 µg/kg, respectively. PAHs with 4-aromatic rings were the dominant compounds, accounting for 51 and 76% of total PAHs in soils and sediments, respectively. The contribution of seven carcinogen PAHs (7CPAHs) in soils and sediments accounted for 43% and 61%, respectively, to ∑PAHs. Among OCPs, p, p’-DDT was the dominant compound in soils, while α-HCH was found to be dominated in sediments. The concentrations of ∑CPs (chlorophenols) were dominated over ∑NPs (nitrophenols) in both the matrices. Various diagnostic tools were applied for the identification of their possible sources in soil and sediments. The observed concentrations of PAHs, OCPs and PCs were more or less comparable with the recently reports from various locations around the world including India. Soil quality guidelines and consensus-based sediment quality guidelines were applied for the assessment of ecotoxicological health effect.

     

Devicyprin induced gonadal impairment in a freshwater food fish, Channa punctatus (Bloch)

Synthetic pyrethroids are the recent major class of broad spectrum, photostable, organic insecticides used in agricultural, domestic and veterinary applications and now account for more than 30% of global insecticide use. Cypermethrin is metabolized and eliminated significantly more slowly by fish than by mammals or birds, which may explain this compound's high toxicity in fish compared to other organisms. The present communication deals with histoanatomical alterations in the gonads of a local fresh water food fish, Channa punctatus exposed to 0.033 ppm (96 hr LC50 X 1/10) concentration of a synthetic pyrethroid, devicyprin (cypermethrin 25%) in aquatic medium of aged tap water for 15, 30 and 45 days respectively. In testis, exposure dependent histological damage has been observed in terms of vacuolization, condensation of spermatogonic cells, distortion of tubular epithelium, shrinkage of interstitial cells and general inflammatory responses. Longest exposure of 45 days has resulted in peculiar starry-sky appearance of the testicular tissue. Gross histo-anatomy of ovarian tissue reveals epithelial lesions, inflammatory responses, stromal hemorrhage, increased interstitium and shrinkage of yolk vesicles towards periphery These findings are quite suggestive of reproductive impairments leading to delayed gonadal maturity and adversely affecting processes of sperm production and ovulation and thus, the fish production.