Thermal Degradation and Kinetics of Alginate Polyurethane Hybrid Material Prepared from Alginic Acid as a Polyol

Alginate polyurethane hybrid materials are prepared by varying mole ratio of 2, 4-TDI as a di-isocyanate and alginic acid as a polyol in presence of dimethyl sulfoxide (DMSO) as a solvent. FT-IR and ¹³C one-dimensional (1D) solid state NMR (SSNMR) spectroscopy indicates that alginic acid is converted into alginate-polyurethane hybrid material via urethane linkage. Surface morphology of alginate-polyurethane hybrids changes by varying alginic acid: TDI ratio. The peak at near 221 °C in DSC thermogram of alginic acid (Alg) is shifted to higher temperature in alginate-polyurethane hybrid (Algpu1 and Algpu2). TGA study shows that alginate-polyurethane hybrid prepared using alginic acid: TDI = 1:1 (Algpu2) is more stable than alginic acid: TDI = 1:0.5 (Algpu1) at 300 °C. Kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as three consecutive 1st order reactions. This study shows that thermal stability of alginate-polyurethane hybrid material was increased by adjusting mole ratio of 2, 4-TDI and alginic acid.     

Biodiesel production from a free fatty acid containing Karanja oil by a single-step heterogeneously catalyzed process

Karanja oil, containing 6.2% free fatty acids (FFAs), was considered for biodiesel production using a single-step solid-phase acid catalyzed process. Different types of zeolites and Amberlyst15 catalysts were tested and biodiesel was produced. Under similar conditions, the highest biodiesel yield was achieved using an Amberlyst15 catalyst, which contained 3–5% of moisture. The effects of operating parameters of the reaction such as reaction temperature, catalyst amount, and methanol-to-oil ratio were studied. An increase of methanol:oil ratio revealed a non-monotonic increase in biodiesel yields. Similar non-monotonic behavior was observed when Jatropha oil was used. Leaching and catalyst reusability were also considered. No significant effects of leaching were observed and catalyst reusability appeared to be affected by methanol interactions. The presence of a co-solvent, Tetrahydrofuran (THF), increased the biodiesel yield. Furthermore, an optimum amount of THF (THF:methanol volume ratio of 1:2) gave rise to the highest biodiesel yield. A biodiesel yield of 93% was achieved at 120 °C using a single-step process with Amberlyst15 as a catalyst, THF as a co-solvent, and a methanol:oil ratio of 30:1.     

Assessing the potentials of Lemna minor in the treatment of domestic wastewater at pilot scale

Water crisis is one of the most serious problems faced by the world today. Phytoremediation is one of the serious efforts towards sustainability. Macrophyte-based wastewater treatment systems have several potential advantages compared with conventional treatment systems. Duckweeds (Lemna spp., Spirodela spp., Wolffia spp.) are small, green freshwater, free-floating aquatic plants. The primary objective of this work was to analyze the role of duckweeds in organic waste and nutrient removal from domestic wastewater being generated from hostels of Birla Institute of Technology, Mesra, Ranchi (India). Interesting results were obtained in which the BOD value reduced by 94.45% and the level of orthophosphate at the end of the work was found to be reduced by 79.39%. The duckweeds flourished well during the experimental period in the pH range of 7 to 8; it can be said that, other factors remaining favorable, the optimum pH for duckweed growth ranges from 7 to 8. Therefore, it can be concluded that this treatment can be successfully carried out on a large scale. Also, it is a low-cost solution to wastewater treatment problems and could satisfy the discharge standards.     

Seasonal and spatial variation of Yamuna River water quality in Delhi, India

Street dust was collected from five roads with different traffic volumes in the metropolitan area of Beijing and separated into five size fractions. Concentrations of polycyclic aromatic hydrocarbons (PAHs) adsorbed on street dust in different size ranges and their correlation with specific surface area and total organic carbon (TOC) were investigated. Results show that the concentration of 16-PAHs of sieved samples ranges from 0.27 to 1.30 mg/kg for all the sampling sites. Particles smaller than 40 μm in diameter have the highest 16-PAHs concentration among all of the size ranges for street dust from the four sampling sites with vehicles running on. PAHs with three or four rings account for 68% of the overall 16-PAHs on average. Remarkable positive correlation exists between 16-PAHs concentration and specific surface area with R ² values from 0.7 to 0.96 for the four sampling sites with vehicles running on. The relationship between the concentration of 16-PAHs and TOC is less clear.     

Limnochemistry and nutrient dynamics in Upper Lake, Bhopal, India

In limnetic ecosystem, water quality depends upon physical, chemical, and biological factors. Effects of temperature, light scattering, and absorption by suspended and dissolved matter, transport, and mixing of nutrients within the lake are the significant factors as far as water quality is concerned. Nutrient loading into the lake and internal cycling of nutrients is always a matter of concern and critical to number of processes. During the winter season, heat and momentum transfer at the lake surface and the temperature-density relation of water destabilize the water column and drive vertical mixing and transport processes. The deepening of the surface layer produces nutrient transfer from the hypolimnion into the euphotic zone of epilimnion. It may also resuspend sediments that would have settled under stratified conditions, or redistribute particles that may still be in suspension. Thus, there exists a complex connection between the hydrodynamics and water quality issues. Present study is an effort to understand how seasonal changes in the limnetic ecosystem regulate the limnochemistry and movement of nutrient. The study revealed that significant variations of nutrients and organic load were observed between epilimnion and hypolimnion during summer season, and the lake was found in hyper-eutrophic condition throughout the study period.     

Water quality assessment of Majhiaon block of Garwa district in Jharkhand with special focus on fluoride analysis

Fluoride in groundwater is known to contaminate the water sources globally. Jharkhand, one of the states in the eastern part of India, is known to have excessive fluoride content in groundwater sources. The present work involves assessment of water quality with special reference to fluoride in Majhiaon block of Garwa district in Jharkhand. Iron, nitrate and arsenic were also tested for the water samples collected from site. Eight hundred forty samples were tested for fluoride on site using colourimetry method, and one tenth of the samples were brought to laboratory for iron, nitrate, arsenic and fluoride analysis. Results show that 402 samples were having fluoride above permissible limit. Iron and nitrate were found to be beyond permissible limits in 302 and 286 water samples, respectively. More than 50% of samples collected from school had fluoride levels above permissible limits. Arsenic was well within the limits. However, few samples shown were excessive of iron and nitrate.     

Monitoring the sedimentary carbon in an artificially disturbed deep-sea sedimentary environment

An area of 0.6 km(2) in the manganese nodule field of the Central Indian Basin was physically disturbed and sediments discharged in the near bottom waters to simulate seabed mining and study its impact on benthic ecosystem. An estimated 2 to 3 tonnes of sedimentary organic carbon (C(org)) was resuspended into the water column during a 9-day experiment. The majority of the sediment cores from within the disturbed area and areas towards the south showed a ~30% increase in C(org) content as well as an increase in carbon burial rates after disturbance, though with a reduction in carbon/phosphorus ratios. High specific surface area (SSA~25 m(2) g(-1)) and low C(org)/SSA ratios (mostly <0.5) are typical of deep-sea sediments. The increased C(org) values were probably due to the organic matter from dead biota and the migration and redeposition of fine-grained, organic-rich particles. Spatial distribution patterns of C(org) contents of cores taken before and after disturbance were used to infer the direction of plume migration and re-sedimentation. A positive relationship was observed between total and labile C(org) and macrobenthos density and total bacterial numbers prior to disturbance, whereas a negative relationship was seen after disturbance owing to drastic reduction in the density of macrofauna and bacteria. Overall decrease in labile organic matter, benthic biota and redistribution of organic matter suggest that the commercial mining of manganese nodules may have a significant immediate negative effect on the benthic ecosystem inducing changes in benthic community structure.     

Studies on urban drinking water quality in a tropical zone

Anthropogenic activities associated with industrialization, agriculture and urbanization have led to the deterioration in water quality due to various contaminants. To assess the status of urban drinking water quality, samples were collected from the piped supplies as well as groundwater sources from different localities of residential, commercial and industrial areas of Lucknow City in a tropical zone of India during pre-monsoon for estimation of coliform and faecal coliform bacteria, organochlorine pesticides (OCPs) and heavy metals. Bacterial contamination was found to be more in the samples from commercial areas than residential and industrial areas. OCPs like α,γ-hexachlorocyclohexane and 1,1 p,p-DDE {dichloro-2, 2-bis(p-chlorophenyl) ethene)} were found to be present in most of the samples from study area. The total organochlorine pesticide levels were found to be within the European Union limit (0.5 μg/L) in most of the samples. Most of the heavy metals estimated in the samples were also found to be within the permissible limits as prescribed by World Health Organization for drinking water. Thus, these observations show that contamination of drinking water in urban areas may be mainly due to municipal, industrial and agricultural activities along with improper disposal of solid waste. This is an alarm to safety of public health and aquatic environment in tropics.     

Changes in anoxic denitrification rate resulting from prefermentation of a septic, phosphorus-limited wastewater.

A preliminary bench-scale study of parallel University of Cape Town (UCT) biological nutrient removal systems showed improvement in anoxic denitrification rates resulting from prefermentation of a septic (i.e., high volatile fatty acid [VFA] content), phosphorus-limited (i.e., total chemical oxygen demand/total phosphorus [TP] ratio < 40:1) wastewater. Net phosphorus removals due to enhanced biological phosphorus removal (EBPR) were only improved marginally by prefermentation in spite of significant increases in anaerobic phosphorus release, polyhydroxyalkanoate formation, and higher anoxic and aerobic uptakes. This probably was due to the high VFA/TP ratio in the raw influent relative to the VFA requirements for EBPR because enough VFAs were already present for phosphorus removal prior to prefermentation. An additional assessment of prefermentation using parallel UCT systems with step feed of 50% of the influent to the anoxic zone was completed. This second phase quantified the effect of prefermentation in a step-feed scenario, which prioritized prefermentation use to enhance denitrification rather than EBPR. While specific denitrification rates in the anoxic zone were significantly improved by prefermentation, high denitrification in the clarifiers and aerobic zones (simultaneous denitrification) made definitive conclusions concerning the potential improvements in total system nitrogen removal questionable. The prefermented system always showed superior values of the zone settling velocity and sludge volume index and the improvement became increasingly statistically significant when the prefermenter was performing well.     

Size-resolved effective density of submicron particles during summertime in the rural atmosphere of Beijing, China

Particle density is an important physical property of atmospheric particles.The information on high time-resolution size-resolved particle density is essential for understanding the atmospheric physical and chemical aging processes of aerosols particles.In the present study,a centrifugal particle mass analyzer(CPMA) combined with a differential mobility analyzer(DMA) was deployed to determine the size-resolved effective density of 50 to 350 nm particles at a rural site of Beijing during summer 2016.The measured particle effective densities decreased with increasing particle sizes and ranged from 1.43 to 1.55 g/cm~3,on average.The effective particle density distributions were dominated by a mode peaked at around 1.5 g/cm~3 for 50 to350 nm particles.Extra modes with peaks at 1.0,0.8,and 0.6 g/cm3 for 150,240,and 350 nm particles,which might be freshly emitted soot particles,were observed during intensive primary emissions episodes.The particle effective densities showed a diurnal variation pattern,with higher values during daytime.A case study showed that the effective density of Aitken mode particles during the new particle formation(NPF) event decreased considerably,indicating the significant contribution of organics to new particle growth.