Experimental investigation of tribological characteristics and emissions with nonedible sunflower oil as a biolubricant

Plant (vegetable) oil has been evaluated as a substitute for mineral oil–based lubricants because of its natural and environmentally friendly characteristics. Availability of vegetable oil makes it a renewable source of bio-oils. Additionally, vegetable oil–based lubricants have shown potential for reducing hydrocarbon and carbon dioxide (CO₂) emissions when utilized in internal combustion (IC) engines and industrial operations. In this study, sunflower oil was investigated to study its lubricant characteristics under different loads using the four-ball tribometer and the exhaust emissions were tested using a four-stroke, single-cylinder diesel engine. All experimental works conformed to American Society for Testing and Materials standard (ASTM D4172-B). Under low loads, sunflower oil showed adequate tribological characteristics (antifriction and antiwear) compared with petroleum oil samples. The results also demonstrated that the sunflower oil–based lubricant was more effective in reducing the emission levels of carbon monoxide (CO), CO₂, and hydrocarbons under different test conditions. Therefore, sunflower oil has the potential to be used as lubricant of mating components.

Implications: An experimental investigation of the characteristics of nonedible sunflower oil tribological behaviors and potential as a renewable source for biofluids alternative to the petroleum oils was carried out. The level of emissions of a four–stroke, single-cylinder diesel engine using sunflower oil as a biolubricant was evaluated.     

Investigations on the effect of chlorine in lubricating oil and the presence of a diesel oxidation catalyst on PCDD/F releases from an internal combustion engine

This paper reports on an intensive study into releases of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated furans (PCDF) and polychlorinated biphenyls (PCB) from a diesel engine and the analysis of PCDD/F and PCB in crankcase lubricating oil. Experimental conditions were set and carefully controlled in order to maximize the possible impact of, and our ability to measure the effect of, changes in the levels of chlorine in the lubricant. Emissions to air were measured using modified EPA methods following the principles of the European EN 1948 standards. A series of 40 experimental runs were completed using three reference lubricants formulated to have three levels of chlorine present as a residual component (at levels of 12, 131 and 259 mg kg(-1) or ppm). The engine was run with and without the diesel oxidation catalyst. All lubricants were realistic oils and the use of unrealistic additives or doping of components - particularly chlorine - in the fuel and lubricant was carefully avoided. Analysis of fuel and lubricant (before and after testing) samples required strenuous attention to achieve acceptable recoveries and showed non-detectable levels of PCB and PCDD/F at a detection limit of around 1.5 ng I-TEQ kg(-1) (ppt), indistinguishable from the laboratory blank. The testing demonstrated the need for extreme care to be taken in developing measurement methods that are sufficiently sensitive for measuring chlorine content of fluids and PCDD/F in oils, the latter being particularly challenging. Mean emissions of PCDD/F with the diesel oxidation catalyst in place were 23 pg I-TEQ l(-1) of fuel and with the diesel oxidation catalyst removed 97 pg I-TEQ l(-1) of fuel. The results of this testing showed that the emissions of PCDD/F were greatly reduced by the presence of a diesel oxidation catalyst in the exhaust, a finding that has not been explicitly tested in previous work. They also show that emissions from the engine were not controlled by the level of chlorine in the lubricant and that emissions did not change in response to a much greater step change in the total chlorine entering the combustion chamber due to a change in the level of chlorine in the fuel. Emissions when the engine was configured with a diesel oxidation catalyst showed a consistent pattern that appears to be unique in the experience of the authors.     

Environmental assessment of ester-based lubricants after application

GOAL, SCOPE AND BACKGROUND: Lubricants based on renewable resources are an environmentally friendly alternative to petrochemical products due to their better ecotoxicological performance and their excellent biodegradability. To improve the technical performance of lubricants, and to reduce friction and wear, the use of additives is nowadays obligatory. The collaborative research center SFB 442 aims at developing environmentally acceptable lubricants that facilitate the avoidance of these additives by transferring their function to suitable coatings. For a complete assessment of the ecological performance of these newly developed lubricants, the whole life cycle including production, application as well as disposal and fate in the environment is studied. In the following study the focus was on the application and its influence on the environmental behavior of the lubricant. The application of lubricants leads, among other things, to the intake of metals due to abrasion from tools, work pieces or mechanical components. Previous examinations indicated a possible influence of metals on the toxicity of eluates prepared from used lubricants (Erlenkaemper et al. 2005). To clarify if the apparent toxicity of used lubricants solely results from the intake of metals, the extractability of these metals from the oil matrix is determined. By combining chemical analyses with bioassays, the bioavailability of metals that are present in the extract is estimated. To further investigate the relevance of metals on toxicity, toxic units (TU) were calculated and related to the results of the bioassays. Interactions between the metals were investigated with aqueous mixtures of metal chlorides and calculations based on the concept of concentration addition and independent action. METHODS: A lubricant mixture was applied to a tribological test bench that simulates real conditions of use and extremely short time load, respectively. Samples were taken at particular times, water soluble fractions (WSF) of these fluids were prepared and dilution series were investigated in several bioassays. Concentration of metals and total organic carbon (TOC) were determined in the eluates. TUs were calculated according to Sprague (1970) and mixture toxicity was calculated according to the concept of concentration addition (Loewe and Muischnek 1926) and independent action (Bliss 1939). RESULTS: Analyses of the metal content of the lubricant and the eluates clearly revealed the availability of the metals in the aqueous extracts. Especially copper, zinc, nickel and chromium were found and their concentrations increased during the time of use. The water extractable fraction, e.g., of copper, rose from 8.8% to 45.3% of the total content in the lubricant after 33.5 hours of use. Tests performed with the algal growth inhibition assay and the luminescence inhibition assay revealed the uptake or absorption by the organisms and, thus, the bioavailability of the metals. The calculation of TUs partly indicated a possible influence of the metals on ecotoxicity of the eluates. Copper reached concentrations equal to or higher than the EC50 value of copper chloride in the growth inhibition assays with algae and Ps. putida as well in the immobilization assay with daphnids. TUs for copper are also larger than 1 for the algal growth inhibition assay. The EL50 values indicated that the luminescence inhibition assay was the most sensitive test system, with values between 4.7% and 9.6%. While the toxicity towards algae and V. fischeri in the growth inhibition assay decreased until both organisms were no longer influenced by the exposure, the EL50 values for the D. magna immobilization assay and the Ps. putida growth inhibition assay decreased with the progressing use of the lubricant. The tested metal salt mixtures showed that Ps. putida, algae and daphnids are the most sensitive organisms with EC50 values below 1 mg/l. DISCUSSION: Although the intake of metals mainly occurred via abrasion of particles, the results revealed the availability of these metals in water. The availability varied for each of the four metals. For both the algal growth inhibition assay and the luminescence inhibition assay, an uptake or absorption of the metals could be demonstrated. The calculated TUs indicated an effect in some bioassays that was not verified in the test itself. The influence of copper on V. fischeri, for example, was not confirmed while the EL50 values for the daphnid bioassay decreased, meaning that the eluates became more toxic with progressing use of the lubricant. The calculations of mixture toxicity based on the concept of concentration addition demonstrated good correlations with the tested metal mixtures, but also a different sensitivity of the organisms. CONCLUSIONS: The results presented here reveal the availability of those metals in water that were taken in during the use of the lubricant in a tribological test bench and, thus, have the possibility of interacting with the organisms. The availability of the metals in the bioassays was proven by chemical analyses. The calculation of TUs and the corresponding EL50 values, however, indicate different availabilities of the metals. The results of the metal salt mixtures show good correlations with calculations of mixture toxicity based on concentration addition. Moreover, the varying sensitivity of the organisms when exposed to eluates or metal mixtures indicates a different bioavailability of the metals and/or the presence of other compounds that exert toxic action. RECOMMENDATIONS AND PERSPECTIVES: For further investigations, the organic oil matrix and its influence on the toxicity have to be taken into account. The toxicity of the eluates may not only be due to metals; additional effects could arise from changes in the lubricant itself.     

Halogenated aromatics from steel production: results of a pilot-scale investigation

The potential environmental impact of emissions of halogenated aromatics from the steel industry is of growing concern. It has been suggested that electric arc furnaces are the only industrial source with constant or increasing emissions of dioxins to air. Here the results are reported from a pilot plant study on how scrap composition and various treatment alternatives affect the formation and release of chlorinated and brominated aromatics. The experiments were conducted with a statistical mixture design, and it is shown that scrap composition has a significant impact on the outcome. In contrast, the various treatment schemes examined--shredding, disassembly, and briquetting--did not affect the formation and release of halogenated aromatics. Parallel experiments with injection of adsorbents showed that it is possible to reduce emissions without substantial investments, and this option is recommended as a low-cost solution.     

The ecotoxicology of vegetable versus mineral based lubricating oils: 3. Coral fertilization and adult corals

Biodegradable vegetable-derived lubricants (VDL) might be less toxic to marine organisms than mineral-derived oils (MDL) due to the absence of high molecular weight aromatics, but this remains largely untested. In this laboratory study, adult corals and coral gametes were exposed to various concentrations of a two-stroke VDL-1A and a corresponding MDL to determine which lubricant type was more toxic to each life stage. In the fertilization experiment, gametes from the scleractinian coral Acropora microphthalma were exposed to water-accommodated fractions (WAF) of VDL-1A and MDL for four hours. The MDL and VDL-1A WAFs inhibited normal fertilization of the corals at 200 microg l(-1) total hydrocarbon content (THC) and 150 microg l(-1) THC respectively. Disturbance of a stable coral-dinoflagellate symbiosis is regarded as a valid measure of sub-lethal stress in adult corals. The state of the symbiosis in branchlets of adult colonies of Acropora formosa was monitored using indicators such as dinoflagellate expulsion and dark-adapted photosystem II yields of dinoflagellate (using pulse amplitude modulation fluorescence). An effect on symbiosis was measurable following 48 h exposure to the lubricants at concentrations of 190 microg l(-1) and 37 microg l(-1) THC for the MDL and VDL-1A respectively. GC/MS revealed that the main constituent of the VDL-1A WAF was the compound coumarin, added by the manufacturer to improve odour. The fragrance containing coumarin was removed from the lubricant formulation and the toxicity towards adult corals re-examined. The coumarin-free VDL-2 exhibited significantly less toxicity towards the adult corals than all of the other oil types tested, with the only measurable effect being a slight but significant drop in photosynthetic efficiency at 280 microg l(-1).     

Primary biodegradability of mineral base oils in relation to their chemical and physical characteristics.

The primary biodegradability of 32 mineral base (i.e., unformulated) oils of paraffinic nature was evaluated using the CEC L-33-A-93 test. These oils were refinery products obtained by varying manufacturing processes. Biodegradation percentages ranged between 15% and 75%, i.e., below the commonly accepted standards for environmentally-compatible lubricants. Biodegradability values were compared to the overall chemical composition and main physical properties of base oils. Biodegradability decreased with increasing levels of aromatic and/or polar compounds in the tested oils. For most oils, the biodegradation percentage increased with the viscosity index, but was a decreasing function of the kinematic viscosity (KV), the pour point, the flash point (FP) and the refractive index (RI). Linear relationships between biodegradability and FP or RI values were observed. These results show that, beside chemical features such as the contents in polar and aromatic compounds, simple physical magnitudes such as KV and RI, commonly used to characterize lubricant properties, may be useful parameters for predicting the biodegradability of mineral base oils.     

Impact of engine lubricant properties on regulated gaseous emissions of 2000-2001 model-year gasoline vehicles

The impact of the sulfur (S) content in lubricating oil was evaluated for four ultra-low-emission vehicles and two super-ultra-low-emission vehicles, all with low mileage. The S content in the lube oils ranged from 0.01 to 0.76%, while the S content of the gasoline was fixed at 0.2 ppmw. Vehicles were configured with aged catalysts and tested over the Federal Test Procedure, at idle and at 50-mph cruise conditions. In all testing modes, variations in the S level of the lubricant did not significantly affect the regulated gas-phase tailpipe emissions. In addition to the regulated gas-phase emissions, a key element of the research was measuring the engine-out sulfur dioxide (SO2) in near-real-time. This research used a new methodology based on a differential optical absorption spectrometer (DOAS) to measure SO2 from the lubricants used in this study. With the DOAS, the contribution of SO2 emissions for the highest-S lubricant was found to range from less than 1 to 6 ppm on a gasoline S equivalent basis over the range of vehicles and test cycles used. The development and operation of the DOAS is discussed in this paper.     

Effects of film mulching on the distribution of phthalate esters in wheat grains from dryland

The application of plastic film in field crop production elevated the phthalate esters (PAEs) accumulation in wheat grains, which poses potential risks to human health. However, the variation of grain PAEs contents in different dryland areas is not clear, and the distribution of PAEs in different tissues of grains has not been studied yet. In the present study, field experiments in five sites (three provinces) with two treatments (soil with and without film mulching) were carried out to study the concentration and distribution of PAEs in grains and the effects of environmental factors on them. Results showed that the total PAE concentration (∑PAEs) in wheat grains ranged from 445 to 764 μg/kg, mainly in the forms of di-(2-ethylhexyl)-phthalate (DEHP), dibutyl phthalate (DBP), and diisobutyl phthalate (DIBP). Compared with control, total PAE concentrations in soils and wheat grains were significantly higher in treatments with film mulching. The effects of film on the proportion of PAEs in the flour and bran varied with experiment sites. Grain PAEs in the control groups presented significantly negative correlation with annual temperature, while there was a positive correlation between soil PAEs and bran PAEs in the film treatment. Results in this study are of great significance to comprehensively evaluate the effect of film mulching on grain safety in dryland wheat production.

     

Basic Research on the Emission of Polycyclic Aromatic Hydrocarbons caused by Waste Incineration

The emission of polycyclic aromatic hydrocarbons (PAH) caused by municipal waste incineration varies according to waste composition and operating parameters such as furnace temperature and excess air. However, to obtain a sample sufficient to measure the emission of PAH at trace levels, it is necessary to operate the incinerator for many hours. Since during these lengthy periods it has not always been possible to maintain stable conditions, it is very difficult to determine the relationship between the emission and waste composition.

In our basic research, therefore, we used municipal waste with an artificially regulated composition for our combustion experiments, and by using an experimental Incinerator we examined the emission behavior of PAH with respect to changes in waste composition and combustion conditions. The following facts were revealed by the results: ? The PAH found in the flue gas were predominantly the more volatile compounds.

? When municipal waste was incinerated at over 850 °C, the concentration of PAH in the flue gas increased rapidly as the proportion of plastics in the waste increased from 0 to 24 percent.

? The elimination of plastics from municipal waste by separate collection and the improvement of combustion conditions can effectively diminish the emission of PAH.

     

Estimating the risks and benefits of pesticides: considering the agroecosystem and integrated pest management in the use of EBDC fungicides on apples

Calculating the risks and benefits of agricultural pesticides determines whether a pesticide will be registered for use on commodities. Historically, the US Environmental Protection Agency (EPA) has used very conservative estimates of health risks, particularly in the absence of data regarding actual use patterns of the pesticide and actual pesticide residue at the point of food purchase. However, when grower groups and manufacturers were faced with the problem of losing the ethylene bisdithiocarbamate (EBDC) fungicides, they approached EPA offering to provide hard data in place of estimates. Plant pathologists familiar with apple agroecosystems pointed out that different fungicides have highly specific uses in integrated pest management (IPM) programs, and that banning EBDC use on apples would probably raise total pesticide use in apples by compromising the pesticide reductions obtained under existing IPM programs. In addition, an early study showed that use-patterns could significantly reduce the amount of EBDC residue on apples. This approach led to a more realistic appraisal of both risks and benefits of the fungicides, lowering risks and raising benefits. The process ended with a registration prescribing use-patterns which result in minimal residue at harvest, thus providing valuable tools for use in IPM programs.     

Generic scenario for the impact of cooling lubricants into the hydrosphere

According to directive 93/67/EEC of the European Commission, this paper deals with the generic exposition evaluation of the environmental concentration of cooling Lubricant chemicals from the metal working industry into the hydrosphere. After considering the relevant life-cycle steps and the selection of a representative point source for the 'reasonable worst case', the emission per day Elocal(water) is determined. It leads to the predicted environmental concentration (PEClocal(water)) for the local stage in the compartment water. In order to gain the PEClocal(water) for an example--a corrosion inhibitor as additive in a cooling lubricant--, the relevant emission paths and the corresponding representative point source are described for the reasonable worst case. For non-water-miscible cooling lubricants, none of the operations in the life cycle leads to a release into the compartment water. To evaluate the hazard potential for cooling lubricant chemicals, the complete risk assessment has to be done. Also, the assessment has to be done for all high production volume chemicals, new substances and existing hazard chemicals. This means that even industrial categories like chemicals used in the textile industry or biocides and others have to be evaluated.     

The biodegradability and microbial toxicity testing of lubricants--some recommendations

In recent years there has been a growing demand for information on the biodegradability (fate) and microbial toxicity (effects) of lubricants. This has been driven by the need to comply with environmental legislation and to meet the requirements of ecolabelling schemes, standards and customer specifications for 'environmentally acceptable' lubricants. This paper describes suitable approaches for generating this information under a variety of environmental conditions (e.g. aerobic, anaerobic, freshwater, marine), gives examples of the results obtained and discusses their interpretation. Recommendations on the use of each test are made.     

Bench-Scale Investigation on Removing Sulfur Dioxide from Flue Gases

The relationship between asbestos consumption and mesothelioma incidence in Connecticut has been investigated.

Asbestos has many industrial applications; however, several of these result in the dissipation of this material (e.g., vehicle brake and clutch lining erosion). In Connecticut, asbestos manufacturing operations contribute approximately 10 tons of airborne asbestos fibers each year, while vehicle brake and clutch lining erosion add another 2 tons. The demolition, especially the “explosive demolition” of buildings which have been fireproofed and/or insulated with asbestos-containing materials may be the most significant future source of asbestos emissions unless adequate precautions are taken.

Occupational asbestos fiber exposure has been known to cause asbestosis, lung cancer, and cancer of the lining of the stomach and lung (mesothelioma) for some time. Recently, the previously rare mesothelial malignancy has been linked to nonoccupational asbestos fiber exposure as well.

There were 133 Conneticut residents diagnosed with mesothelioma between 1935 and 1972. Although subject to diagnostic error, available statistics suggest that the combined sex age-adjusted mesothelioma incidence rate (AAR) per 100,000 Connecticut population has exhibited a possible 10-fold increase since 1935, rising from 0.02 during 1940 to 1949 to 0.25 from 1960 to 1969. The trends for both men and women also showed sharp increases over the same time period (1940 to 1970). The rapid rise in Connecticut's mesothelioma incidence rate closely follows the increase in the State's cumulative asbestos consumption and suggests a linearly increasing cause-effect relationship.     

Study on the co-effect of maifanite-based photocatalyst and humic acid in the photodegradation of organic pollutant

Environmental Science and Pollution Research - In this study, the co-effect of clay mineral-based photocatalyst and humic acid on the photodegradation of dye was revealed for the first time. The...     

Effects of Fuel Variables on Diesel Emissions

The body of information presented in this paper is directed towards engineers in the field of environmental sciences involved in measuring and/or evaluating the emissions from a variety of diesel engines or vehicles. This paper summarizes recent data obtained by EPA on identification and quantification of different emissions (i.e. characterization) from a variety of diesel engines.

Extensive work has been done comparing emissions from some light duty diesel and gasoline passenger cars. The work on the diesel vehicles was expanded to include tests with five different diesel fuels to determine how fuel composition affects emissions. This work showed that use of a poorer quality fuel frequently made emissions worse. The investigation of fuel composition continued with a project in which specific fuel parameters were systematically varied to determine their effect on emissions. EPA is presently testing a variety of fuels derived from coal and oil shale to determine their effects on emissions.

EPA has also tested a heavy duty Volvo diesel bus engine designed to run on methanol and diesel fuel, each injected through its own injection system. The use of the dual fuel resulted in a reduction in particulates and NO _x but an increase in HC and CO compared to a baseline Volvo diesel engine running on pure diesel fuel.

Finally, some Ames bioassay tests have been performed on samples from the diesel passenger cars operated on various fuels and blends. An increase in Ames test response (mutagenicity) was seen when the higher aromatic blend was used and also when a commercial cetane improver was used. Samples from the Volvo diesel bus engine fueled with methanol and diesel fuel showed that use of a catalyst increased the Ames response.     

The Influence of Gasoline Formulation on Specific Pollutant Emissions

ABSTRACT

Many recent works have dealt with the influence of fuel composition on regulated and specific pollutant emissions from spark ignition engines. While many qualitative correlations have been already proposed, only a few quantitative ones are known (benzene remains an exception).

This paper describes qualitative and quantitative correlations between fuel composition and specific pollutant emissions (individual hydrocarbons, aldehydes, ketones, alcohols, and organic acids) of a spark ignition engine. The aim of this work was to find the precursors of the main specific pollutants. Then, for each of them, a multilinear equation has been calculated, illustrating the correlation between its concentration in exhaust gases and its content in the fuel. The results of these calculations point out which initial compound favors the formation of a determined pollutant. As lean conditions are probably going to be used in future commercial engines, the fuel effect has been studied for a broad range of equivalence ratios (from 0.8 to 1.2).     

Parametrization of groundwater quality of the Quaternary aquifer in N’Djamena (Chad), Lake Chad Basin: application of numerical and multivariate analyses

The urban groundwater of the Quaternary aquifer of the Lake Chad basin in N’Djamena has been subject to many hydrochemical studies. However, the results are often not presented in a way that enables water quality managers to make an appropriate decisions, which restrict development and poverty reduction efforts. The objective of the present study was to contribute the improved management of the local groundwater resources. A total of 85 groundwater samples were interpreted using hydrochemical techniques associated with integrated numerical indices and multivariate statistical analysis. The hydrochemical results coupled with the relative residence time of water have shown that the chemical composition of these waters is linked to geogenic and anthropogenic factors and to their proximity to the Chari-Logone rivers. These investigations showed that the groundwater quality in N’Djamena is characterized by a high spatial variability. This study also assessed the suitability of groundwater for user needs and identified areas which are more/less favorable for a specific use. The evaluation of water quality and its suitability for human consumption is also a problem of optimizing data acquisition strategy, and this study used the correlation between water quality index (WQI) and electrical conductivity (EC) to orientate future data acquisition strategies. This parametrization can assist the decision makers and water management professionals in evaluating groundwater availability and setting up a robust water quality management plan in areas with similar hydrogeological and climatic conditions.

     

A systematic review on cigarette butt management as a hazardous waste and prevalent litter: control and recycling

Annually, over 5.5 trillion cigarettes are produced worldwide, and it is estimated that 4.5 trillion cigarette butts (CBs) are still being littered in the world. The dispersal of the CBs has caused this hazardous waste to be considered as one of the most important litters and environmental risks all over the world. This systematic study with the search protocol definition and keyword identification was developed to find the CBs control and recycling methods by searching in five scientific databases. Founded articles were monitored and finally, 35 related articles were selected and studied by the authors. The results of this study showed that CBs recycling methods have been tested in 10 specific categories all over the world. The CBs have been applied without any pre-processing methods in the bricks and asphalt production. However, other applications of the CBs such as the absorbent material production, vector control, and use as a biofilm carrier in wastewater treatment need various processing methods. The researchers also presented models and suggestions such as taxes, penalties, and public education for the control of CBs littering. Despite the innovative methods applied for the CBs recycling in previous studies, CBs have not received much attention in terms of pollutant control and environmental issues in recycling processes.

     

Are photocatalytic processes effective for removal of airborne viruses from indoor air? A narrative review

A wide variety of methods have been applied in indoor air to reduce the microbial load and reduce the transmission rate of acute respiratory diseases to personnel in healthcare sittings. In recent months, with the occurrence of COVID-19 pandemic, the role of portable ventilation systems in reducing the load of virus in indoor air has received much attention. The present study delineates a comprehensive up-to-date overview of the available photocatalysis technologies that have been applied for inactivating and removing airborne viruses. The detection methods for identifying viral particles in air and the main mechanisms involving in virus inactivation during photocatalysis are described and discussed. The photocatalytic processes could effectively decrease the load of viruses in indoor air. However, a constant viral model may not be generalizable to other airborne viruses. In photocatalytic processes, temperature and humidity play a distinct role in the inactivation of viruses through changing photocatalytic rate. The main mechanisms for inactivation of airborne viruses in the photocatalytic processes included chemical oxidation by the reactive oxygen species (ROS), the toxicity of metal ions released from metal-containing photocatalysts, and morphological damage of viruses.

     

Nitrate contamination in water resources,human health risks and its remediation through adsorption: a focused review

The level of nitrate in water has been increasing considerably all around the world due to vast application of inorganic nitrogen fertiliser and animal manure. Because of nitrate’s high solubility in water, human beings are getting exposed to it mainly through various routes including water, food etc. Various regulations have been set for nitrate (45–50 mgNO₃^?/L) in drinking water to protect health of the infants from the methemoglobinemia, birth defects, thyroid disease, risk of specific cancers, i.e. colorectal, breast and bladder cancer caused due to nitrate poisoning. Different methods like ion exchange, adsorption, biological denitrification etc. have the ability to eliminate the nitrate from the aqueous medium. However, adsorption process got preference over the other approaches because of its simple design and satisfactory results especially with surface modified adsorbents or with mineral-based adsorbents. Different types of adsorbents have been used for this purpose; however, adsorbents derived from the biomass wastes have great adsorption capacities for nitrate such as tea waste-based adsorbents (136.43 mg/g), carbon nanotube (142.86 mg/g), chitosan beads (104 mg/g) and cetyltrimethylammonium bromide modified rice husk (278 mg/g). Therefore, a thorough literature survey has been carried out to formulate this review paper to understand various sources of nitrate pollution, route of exposure to the human beings, ill effects along with discussing the key developments as well as the new advancements reported in procuring low-cost efficient adsorbents for water purification.