Jyoti Chawla

Removal of Cadmium Ion from Water/Wastewater by Nano-metal Oxides: A Review

Environmental water samples contain wide range of contaminants including heavy metal ions that are required only in trace amount. Excessive level of metal ions in water may be detrimental to health and environment. Heavy metal poisoning has been a serious concern all over the globe. Heavy metals are well known to be non-biodegradable and tend to bio-accumulate at various concentrations. A number of methods have been proposed to remove heavy metal ions from water and among them adsorption is one of the best methods. Cadmium has been identified as one of the toxic heavy metals that enters the water through disposal of waste from industries. The increasing technological use of cadmium has raised the concern for its removal from water/wastewater. This review article provides an overview of use of nano-metal oxides as adsorbents for removal of cadmium from water/wastewater. This study involves the identification of environmentally friendly, low-cost and efficient nano-metal oxide sorbents for water/wastewater purification. A detailed comparison of reported nano-metal oxide sorbents has been done in order to rank them and to predict the knowledge gaps in this area.

Cloud Point Studies of Tween and Glycol in the Presence of Salts

This article deals with the cloud point studies of ethoxylated sorbitan ester, Tween in the presence of glycols, and salts. Cloud point temperature of Tween 20 (5 mol dm−3) and Tween 80 (1 mol dm−3) has been determined in the presence of various salts in addition to glycols. The glycols chosen for these studies were triethylene glycol (TEG), and ethylene glycol mono butylether (EGMBE). At concentration below 0.02 M these salts have no significant effect on cloud point temperature in all cases. The cloud point temperature of Tween+TEG and Tween+EGMBE found to decrease in the presence of sodium chloride (NaCl) and potassium chloride (KCl). The cloud point temperature of Tween 20 + TEG and Tween 20 + EGMBE found to increase in the presence of urea and nicotinamide. The change in cloud point was found to be more in case of nicotinamide as compare to urea. The influence of an additive on the cloud point depends on how it affects the intermicellar interactions. An effort has been made to understand the interaction between solvent and additives leading to a change in solubility of Tween.

Removal of cadmium ion from wastewater by carbon-based nanosorbents: a review

A green environment and a healthy life are dream projects of todays science and technology to save the world. Heavy metal ions in water affect both environment and human health. Cadmium has been identified as one of the heavy metals that causes acute or chronic toxic effects if ingested. Increasing use of cadmium in different technological fields has raised concern about its presence and removal from water/wastewater. Researchers have made many systematic efforts to remove heavy metals from water to reduce their impact on human beings and the environment. Adsorption is one of the best methods to remove heavy metals from water among the different proposed methods. This study explores carbon-based nanosorbents which have been proved as effective adsorbents for removal of cadmium ions from water. The adsorption efficiency of carbon-based nanosorbents is the main criterion to rank and select them for removal of cadmium ions from water. Toxicity, reusability and environmentally friendly characteristics of sorbents are also taken considered while ranking the suitable carbon-based nanosorbents for removal of cadmium ions from water.

Spectrophotometric determination of triclosan based on diazotization reaction: response surface optimization using Box–Behnken design

A spectrophotometric method based on diazotization of aniline with triclosan has been developed for the determination of triclosan in water samples. The diazotization process involves two steps: (1) reaction of aniline with sodium nitrite in an acidic medium to form diazonium ion and (2) reaction of diazonium ion with triclosan to form a yellowish-orange azo compound in an alkaline medium. The resulting yellowish-orange product has a maximum absorption at 352 nm which allows the determination of triclosan in aqueous solution in the linear concentration range of 0.1-3.0 μM with R2 = 0.998. The concentration of hydrochloric acid, sodium nitrite, and aniline was optimized for diazotization reaction to achieve good spectrophotometric determination of triclosan. The optimization of experimental conditions for spectrophotometric determination of triclosan in terms of concentration of sodium nitrite, hydrogen chloride and aniline was also carried out by using Box-Behnken design of response surface methodology and results obtained were in agreement with the experimentally optimized values. The proposed method was then successfully applied for analyses of triclosan content in water samples.

Assessing Exposure of Fullerenes/Functionalized Fullerenes from Water: Risk, Challenges, and Knowledge Gaps

Fullerenes may be introduced to water during the life cycle/processing/disposal of products leading to the exposure of fullerene to human beings. The review of human health risk assessment (HHRA) studies indicated that very few studies have focused on exposures of specific carbon-based materials from water medium, indicating a knowledge gap. To understand difficulty in conducting HHRA, this study focused on identifying knowledge gaps in occurrence and toxicity data for assessing exposure risks of fullerenes in water using published studies. Knowledge gaps in four important areas were observed: (i) levels of fullerenes in water and fish tissues, (ii) oral exposure of fullerene, (iii) dermal exposure of fullerene, and (iv) conditions used in toxicity studies. This study proposed suggestions for addressing these knowledge gaps which could aid in assessing health risks of fullerene exposures from water route.

Reducing the Toxicity of Carbon Nanotubes and Fullerenes Using Surface Modification Strategy

Carbon-based nanoparticles have attracted much attention because of their unique properties like specific strength, lightness, electrical properties and also show several promising potential applications in biology and pharmacology. However, their growing use and mass production have raised several questions about their probable unfavourable effects on human health. For example, use of carbon nanotubes (CNTs) and fullerenes are there in maximum number of consumer products containing carbon-based nanomaterials and have been reportedly found in environmental samples (Farre et al. 2010).

Identifying Challenges in Assessing Risks of Exposures of Silver Nanoparticles

Silver nanoparticles (AgNPs) find applications in many consumer products due to their unique properties. It is imperative to contend with the safety issues in respect of AgNPs during manufacturing, usage, and after disposal, as manufacturers as well as consumers are likely to be exposed to these particles. This review seeks to scrutinize the current challenges in obtaining input parameters for conducting risk assessment of exposure to Ag NPs and specifically focuses on exposures of humans to Ag NPs through oral ingestion of Ag NPs via edible parts of plants, water, soil ingestion, and fish, and through dermal uptake exposure pathways. The present status of toxicological studies of silver nanoparticles and challenges in assessing risks of exposure to silver nanoparticles has been discussed in detail. The limited and contradictory existing data imply that prudence must be exercised when potential exposures to silver nanoparticle emerge from different routes.