Showing papers by "Indumathi M. Nambi published in 2016"
TL;DR: MZVI particles showed consistent phenol degradation at circum-neutral pH with efficiency of 44, 67%, and 89% in a span of 5, 10 and 20 min respectively and the dissolved iron species and residual iron formation were measured as a function of pH.
45 citations
TL;DR: It is demonstrated that chemical depassivation can restore considerable reactivity of ZVI in the existing permeable reactive barriers and make it suitable for effective water treatment applications.
34 citations
TL;DR: In this paper, low temperature synthesis of carboxymethyl cellulose (CMC) stabilized nano zero valent iron (nZVI) hybrid, where Fe 2+ ion was sandwiched between CMC and nZVI.
33 citations
TL;DR: The study suggests that the initial estimation of the composition of a fuel is crucial in evaluating dissolution processes due to ideal and non-ideal dissolution, and in predicting long term dissolution trends and the longevity of NAPL petroleum plume risks.
21 citations
TL;DR: In this article, an attempt was made to evaluate the reactive transport of ammonium nitrogen under continuous and alternate wetting and drying mode (AWD) of irrigation in soil columns using a HYDRUS 2D model.
17 citations
TL;DR: In this paper, a low molecular heterocyclic aminopyrazine (Apy)-reduced graphene oxide (r-GO) hybrid coated carbon cloth electrode was employed as an active and stable bio-electro catalyst in a microbial fuel cell (MFC).
Abstract: In the present study, a low molecular heterocyclic aminopyrazine (Apy)–reduced graphene oxide (r-GO) hybrid coated carbon cloth (r-GO–Apy–CC) was employed as an active and stable bio-electro catalyst in a microbial fuel cell (MFC). The presence of imine (–NH–) and pyridinic (–NC–) functional groups on the r-GO–Apy–CC electrode plays a critical role in the formation of bacterial colonization and enhanced extracellular electron transfer (EET) over a considerable period. The bacterial colonization over the r-GO–Apy–CC electrode was investigated in a Sacrificial Electrode Mode Reactor (SEMR) in which attached bacterial density with extracellular polysaccharides was monitored over a period. Simultaneously, cyclic voltammetry (CV) was performed in a bioelectrochemical system (BES) reactor, resulting in an increased current density–voltage response from 0.27 mA cm−2 to 1.84 mA cm−2 over a period of time. In addition, when r-GO–Apy–CC was employed as an anode in MFC, the power density was nearly two times (1253 mW m−2) than that of the MFC employed with plain carbon cloth (PCC) (663.7 mW m−2) at a steady state condition. It was proposed that the combined effect of Apy hybridized with nanostructured r-GO provides a large surface area for bacterial colonization. Moreover, the high bioelectrocatalytic activity was attributed to the low molecular nature of the Apy, which incorporated well into the EET pathway of the exoelectrogens by a redox mechanism.
14 citations
TL;DR: In this article, the authors addressed the transport of nitrogenous fertilizers such as ammonium and nitrate in the presence of organic carbon (acetate) in a one-dimensional soil column under saturated conditions, considering the effect of adsorption and biotransformation.
Abstract: The vertical transport of nitrates from fertilizer application and wastewater irrigation through the subsurface and saturated zone is of major concern to assess the vulnerability of groundwater contamination. The present study addresses the transport of nitrogenous fertilizers such as ammonium and nitrate in the presence of organic carbon (acetate) in a one-dimensional soil column under saturated conditions, considering the effect of adsorption and biotransformation. The soil had a neutral pH range and was classified as loamy sand, with a 0.89% organic carbon content. Batch studies revealed that sorption occurred in the order of ammonium > acetate > nitrate following a Freundlich isotherm model. Mixed heterotrophic native soil bacteria for aerobic nitrification and anoxic denitrification were developed, and the growth kinetic parameters were simulated using a Haldane inhibition model for nitrification and a Monod inhibition model for denitrification. Results from biotransformation studies suggeste...
10 citations
TL;DR: In this paper, a detailed chemical speciation study was carried out to reveal the pH dependent multi-kinetic trend and Cr 6+ reduction mechanism, especially at neutral and alkaline pH conditions.
Abstract: Nano zero valent iron (nZVI) of 0 particles. The catalytic performance of MeOH 45 -nZVI was assessed using model pollutant Cr 6+ at different aspects such as varying pH, initial concentration of MeOH 45 -nZVI and Cr 6+ . A detailed chemical speciation study was carried out to reveal the pH dependent multi-kinetic trend and Cr 6+ reduction mechanism, especially at neutral and alkaline pH conditions. Regression equations were developed for Cr 6+ reduction at every stage of reaction, considering significant Fe species; and the new model was assessed for quality of fit and adequacy. The passive layer on MeOH 45 -nZVI was evidenced with differential interference contrast (DIC) images and analyzed for chemical composition that further supported the proposed mechanisms. Also, chemical speciation study confirmed that acidic pH is more favorable not only in terms of accelerated kinetics, but also in lesser iron utilization/gm of Cr 6+ removed. Furthermore, MeOH 45 -nZVI produced trace amount of Fe ions and sludge at the end of the reaction, favoring it as an ideal choice of packing material for point of use drinking water treatment and other environmental applications.
10 citations
TL;DR: Although the effect of non-ideality decreased with distance from the source, the assumption of spatially varying residual saturation could effectively illustrate post-spill scenario by estimating the consequent decrease in mass transfer rate.
7 citations
TL;DR: In this article, a one-dimensional numerical model is developed to simulate the transport of pesticides in an unsaturated porous medium, considering the effect of adsorption and microbial degradation with inhibition in addition to conventional advective and dispersive transport.
Abstract: The vertical transport of pesticides from a surface application through an unsaturated porous medium system is of major concern to assess the vulnerability of groundwater contamination. In order to better understand the transport of pesticides in the groundwater, it is essential to understand the flow and predict the pesticide concentration in the unsaturated zone. A one-dimensional numerical model is developed to simulate the transport of pesticides in an unsaturated porous medium, considering the effect of adsorption and microbial degradation with inhibition in addition to conventional advective and dispersive transport. The effect of unsaturated soil parameters on the water flow dynamics and the factors governing the pesticide transport in an unsaturated porous medium is also numerically investigated. The numerical results suggest that the adsorption and biodegradation is an important sink in contaminant removal. In addition, the microbial growth inhibition due to pesticide restricts the potent...
7 citations
TL;DR: In this paper, the authors investigated dissolution characteristics of residual petroleum hydrocarbons resulting from both mobile and immobile domains under varying conditions of rate-limited diffusive mass transfer, longitudinal dispersivity and mean mobile fluid velocity in a saturated groundwater system.
Abstract: Petroleum hydrocarbons generally referred to as light non-aqueous phase liquid (LNAPL) entrapped within a saturated subsurface geological formation can result in longer duration of contamination due to mass transfer limitations associated with heterogeneity of the system. Considering a part of the total pore volume as immobile is significant in capturing the behaviour of extended tailing by solute breakthrough profiles. In this context, the present numerical model investigates dissolution characteristics of residual petroleum hydrocarbons (LNAPL) resulting from both mobile and immobile domains under varying conditions of rate-limited diffusive mass transfer, longitudinal dispersivity and mean mobile fluid velocity in a saturated groundwater system. The numerical results suggest that the influence of residual LNAPL saturation on dissolution mass transfer coefficient is critical in comparison with mobile flow velocity and dispersivity. In addition, the rate-limited effect becomes predominant with significan...
TL;DR: In this article, a simulation study is conducted based on the one-dimensional numerical model considering Richard's equation for unsaturated water flow and solute transport which takes into account the effect of both adsorption and biodegradation with inhibitory effect to understand pesticide transport in an unsaturated porous medium.
Abstract: The pesticides applied on the soil surface can be transported vertically downwards through the unsaturated porous system and lead to groundwater contamination. Proper agricultural management practices such as selection of appropriate irrigation techniques, choosing proper irrigation rates, and application of optimum pesticide dosages are necessary to prevent leaching of pesticides to greater depths thus preventing groundwater contamination. A simulation study is conducted based on the one-dimensional numerical model considering Richard’s equation for unsaturated water flow and solute transport which takes into account the effect of both adsorption and biodegradation with inhibitory effect to understand pesticide transport in an unsaturated porous medium. The study addresses the influence of irrigation rate, type of irrigation, and pesticide dosage on soil moisture and pesticide concentration distribution. The numerical results suggest that higher water application rates can carry the pesticides to greater depths. Pulsed irrigation can slightly reduce water losses through the root zone when compared to continuous irrigation. The comparison of the wetting patterns and the pesticide distribution obtained in continuous and pulsed irrigation helps to decide the use of a particular irrigation strategy in order to achieve suitable goals. In addition, the results from this study bring out better understanding of the effect of pesticide concentration and dosage on the resultant pesticide distribution in the unsaturated zone and the pesticide potential to cause groundwater contamination. The better analysis of outputs from this study can help in improving and designing better agricultural management strategies, carrying out risk assessment and bioremediation studies.