Krishna Kadirvelu

Agricultural solid wastes for the removal of heavy metals: Adsorption of Cu(II) by coirpith carbon

Abstract Adsorption studies of Cu(II) from aqueous solutions on carbonized coirpith were carried out under varying conditions of agitation time, metal ion concentration, adsorbent dose, and pH. Adsorption equilibrium was reached in 25 min for 20 – 50 mg/L concentrations of copper(II). Kinetics of adsorption obeyed a first order rate equation. The per cent removal increased from 50 to 90 with the increase of pH from 2.0 to 4.0 and remained constant to pH 10.0 for a Cu(II) concentration of 20 mg/L. Adsorption equilibrium followed both Langmuir and Freundlich isotherms.

Separation of Mercury(II) from Aqueous Solution by Adsorption onto an Activated Carbon Prepared from Eichhornia Crassipes

The adsorption of mercury(II) from aqueous solutions onto an activated carbon derived from Eichhornia crassipes (AEC) was investigated under varying conditions of agitation time, metal ion concentration, adsorbent dose and pH to assess the kinetic and equilibrium parameters. Adsorption equilibrium was attained in 200, 310, 360 and 360 min for 10, 20, 30 and 40 mg/l Hg(II) concentrations. The first- and second-order adsorption rate constants were calculated and the experimental equilibrium adsorption capacities (qe) for different initial Hg(II) concentrations were reported. Adsorption was dependent on the solution pH, the Hg(II) concentration, the carbon concentration and the contact time. Both the Freundlich and Langmuir adsorption isotherm models fitted the experimental data well. The adsorption capacity was found to be 28.4 mg/g at pH 5 for a particle size of 125–180 μm. The adsorption capacity of the carbon produced met commercial conditions and was found to be superior to that of many other adsorbents. The percentage removal increased as the pH value of the solution was increased from 2 to 5 and then remained constant up to a pH value of 10. Desorption studies were performed with dilute hydrochloric acid and potassium iodide (KI) solutions.

Zearalenone induced embryo and neurotoxicity in zebrafish model ( Danio rerio ): Role of oxidative stress revealed by a multi biomarker study

In the present study, we evaluated the zearalenone induced adverse effects in zebrafish embryos using various endpoints like embryo toxicity, heart rate, oxidative stress indicators (reactive oxygen species (ROS), lipid peroxidation (LPO), Nitric oxide (NO)), antioxidant responses (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase enzyme (GST) and reduced glutathione (GSH), metabolic biomarkers (lactate dehydrogenase (LDH) and Nitric oxide (NO)), neurotoxicity (acetylcholinesterase (AChE)), genotoxicity (comet assay and acridine orange staining (AO)) and histological analysis. In this study, four concentrations 350, 550, 750 and 950u202fμg/L of ZEA were chosen based on LC10 and LC50 values of the previous report. The results shows that ZEA induces developmental defects like pericardial edema, hyperemia, yolk sac edema, spine curvature and reduction in heart rate from above 550u202fμg/L exposure and the severity was increased with concentration and time dependent manner. Significant induction in oxidative stress indices (ROS, LPO and NO), reduction in antioxidant defence system (SOD, CAT, GPx, GST and GSH) and changes in metabolic biomarkers (LDH and AP) were observed at higher ZEA exposed concentration. Neurotoxic effects of ZEA were observed with significant inhibition of AChE activity at higher exposure groups (750 and 950u202fμg/L). Moreover, we also noticed DNA damage, apoptosis and histological changes in the higher ZEA treatments at 96u202fh post fertilization (hpf) embryos. Hence, in the present study we concluded that oxidative stress is the main culprit in ZEA induced developmental, genotoxicity and neurotoxicity in zebrafish embryos.

Toxicity assessment of pyriproxyfen in vertebrate model zebrafish embryos ( Danio rerio ): A multi biomarker study

Pyriproxyfen (2-[1-methyl-2-(4-phenoxyphenoxy) ethoxy] pyridine) (PPF), a pyridine-based pesticide widely used to control agricultural insect pests and mosquitoes in drinking water sources. However, its ecotoxicological data is limited in aquatic vertebrates particularly in fish. Hence, the present study aimed to evaluate the adverse effect of PPF in zebrafish embryo development (Danio rerio). In order to investigate the impact of PPF, embryos were exposed to 0.16, 0.33 and 1.66u202fμg/mL (0.52, 1.04 and 5.2u202fμM, respectively) for 96 hpf and various biomarker indices such as developmental toxicity (edema formation, hyperemia, heart size and scoliosis), oxidative stress (reactive oxygen species (ROS), lipid peroxidation (LPO) and nitric oxide (NO)), antioxidant responses (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx) and reduced glutathione (GSH)), biochemical (lactate dehydrogenase (LDH) and acid phosphatase (AP)), neurotoxicity (acetylcholinesterase (AChE)), genotoxicity (apoptosis and DNA damage) and histopathological changes were determined. The results showed that severe developmental deformities and changes in heart rate were observed in embryos treated with highest (1.66u202fμg/mL) concentration than the control (Pu202f<u202f0.05). Heart size measurement showed that, significant change in heart size (Pu202f<u202f0.01) was observed in embryos of 96 hpf only at 1.66u202fμg/mL PPF exposure. The oxidative stress was apparent at highest test concentration (1.66u202fμg/mL) as reflected by the elevated ROS, LPO and NO and changes in antioxidant enzyme activities including SOD, CAT, GST and GPx (Pu202f<u202f0.05). Besides, GSH level and AChE activity were significantly lowered in 1.66u202fμg/mL PPF exposed group than the control. After 96 hpf of PPF exposure, no significant changes were found in AP activity whereas, a biphasic response was observed in the LDH activity. There was no genotoxic effect in embryos exposed to PPF at 0.16 and 0.33u202fμg/mL, while significant (Pu202f<u202f0.05) DNA damage and apoptosis were found in 1.66u202fμg/mL treated group. Histopathological analysis revealed that exposure to PPF at 1.66u202fμg/mL resulted in thinning of heart muscles, pericardial edema and hyperemia while there was no obvious changes were observed in other treatment groups. Hence, the results of the present study demonstrate that PPF could cause adverse effect on early developmental stages of zebrafish at higher concentration.

Highly reactive lanthanum doped zinc oxide nanofiber photocatalyst for effective decontamination of methyl parathion

Polyacrylonitrile (PAN) nanofibers were produced using electrospinning technique and La doped ZnO Nanorods was immobilized to enhance photo catalytic activity for the decontamination of organo-phosphorous compounds. La doped ZnO nanorods were synthesized by hydrothermal method and characterized by FTIR, XRD, SEM, TEM, TGA and BET studies. The photo catalytic decontamination studies were carried out to evaluate the catalytic activity using methyl parathion under UV irradiation method and 99.6% removal efficiency was obtained within 1xa0h reaction time. The secondary compounds were analysed using UV–VIS Spectrophotometer and confirmed by HPLC and GC-MS.

Photo-decontamination of p-nitrophenol using reusable lanthanum doped ZnO electrospun nanofiber catalyst

P-nitrophenol is a common persistent pollutant present in industrial waste water. Photocatalytic degradation of organic pollutants is an efficient method of detoxification that has been well established. This study investigates the novel method of photocatalytic degradation using Lanthanum doped zinc oxide nano rods synthesized by hydrothermal technique and impregnated on PAN nanofiber (La doped ZnO NF). The functionalized La doped ZnO nanofiber was characterized by XRD, SEM, TEM and STA. The residual concentration and mineralization of p-nitrophenol were assessed using UV–Vis spectrophotometer and Total organic carbon analyzer. The catalytic properties remained unchanged even after multiple cyclesof degradation. Repeat cycles of remediation showed consistent efficiency rate of 92% proving its cost-effectiveness and viability. The photocatalytic performance of La doped ZnO NF was investigated on p-nitrophenol in optimized experimental conditions. The process may be an economically viable process for upscaling photocatalytic degradation processes.

Strategies to design modified activated carbon fibers for the decontamination of water and air

The rapid industrialization has induced the entry of organic and inorganic contaminants into the environment at a rate greater than environmental cleaning. As a consequence, pollutants have accumulated in environmental media, thus posing health risk for living organisms. Here, we present surface treatment strategies that modify physicochemical properties of activated carbon fibers for environmental remediation. In particular, we review metals, metal oxides and various advanced materials used for modifying activated carbon fibers. We discuss the utilization of modified activated carbon fibers for adsorption of organic pollutants and inorganic pollutants, and for thexa0degradation of organic pollutants by photocatalysis, electrocatalysis, Fenton process and dielectric barrier discharge. We also discuss air pollutant removal, capacitive deionization, removal of inorganic ions and microbial decontamination by modified activated carbon fibers.