Manas Bandyopadhyay

Performance of Waste Activated Carbon as a Low-Cost Adsorbent for the Removal of Anionic Surfactant from Aquatic Environment

Abstract In the present study, different low cost adsorbents were screened for their sodium dodecyl sulfate (SDS, an anionic surfactant) removal capacity. Waste activated carbon (WAC) from the aqua purifier has shown high efficiency for SDS removal. The performance evaluation in the presence of various ions (Ca2+, , and Cl−) and at various pH was studied. Desorption studies were conducted using simple sonication and pH variation technique. Column adsorption studies were performed. SEM and EDS studies were done on the adsorbing material before adsorption, after adsorption and after desorption of SDS.

Adsorption of anionic surfactant on alumina and reuse of the surfactant-modified alumina for the removal of crystal violet from aquatic environment

Abstract The adsorption characteristics of sodium dodecyl sulfate (SDS), an anionic surfactant on neutral alumina were studied in detail. Alumina was found to be an efficient adsorbent for SDS and could be used for the removal of SDS from its highly concentrated (several thousand ppm) solution. The equilibrium time found was 2 h. Though the removal efficiency was low (∼65%) at neutral pH, but in slightly acidic condition and in the presence of NaCl the efficiency could be increased dramatically (up to >98%). The adsorption isotherm study showed distinct four regions. The effects of various other parameters such as adsorbent dose, time, and the presence of different ions (Cl- NO- 3, SO2- 4, and Fe3+), and nonionic surfactant on the SDS adsorption were also studied. It was observed that the adsorption capacity was increased due to the presence of these ions in general. After the adsorption of SDS on alumina, the surfactant-modified alumina (SMA) was used for the removal of crystal violet (CV), a well-known cationic dye from aquatic environment. The kinetic studies showed that 1 h shaking time was sufficient to achieve the equilibrium. The removal of CV followed the second order kinetics. Studies were conducted to see the effects of adsorbent dose and initial CV concentration on the removal of CV using SMA. The pH was maintained at 6.7 ± 0.1. SMA was found to be very efficient, and ∼99% efficiency could be achieved under optimised conditions for the removal of CV when present even at a high concentration (200 ppm). To test whether the removal of CV was possible from real water using SMA, the adsorption study was conducted using CV spiked samples using distilled water, tap water, and synthetically prepared wastewater. It was interesting to note that the removal efficiency was even better for tap water and much better for wastewater when compared to that using distilled water. Desorption of both SDS and CV from the SMA surface was possible using 1 M sodium hydroxide solutions.

ADSORPTION OF ANIONIC SURFACTANT BY A LOW-COST ADSORBENT

ABSTRACT This study was undertaken to evaluate the efficiency of rubber granule, a low-cost adsorbent for the removal of sodium dodecyl sulfate (SDS) that is a representative member of anionic surfactant (AS). In the batch experiments conducted at an initial concentration range of 2–6 mg/l, it was found that the rubber granules selected could remove SDS from water up to 90%. Kinetic profiles were developed for various conditions. Effects of adsorbent size, initial adsorbate concentration and adsorbent dose, pH, Ca2+ ion concentration, Fe2+ ion concentration, Cl− ion concentration, and ionic strength on the adsorption of SDS on rubber granules were studied. The adsorption isotherm studies were also conducted.

ANAEROBIC TREATMENT OF ATRAZINE BEARING WASTEWATER

Performance of mixed microbial anaerobic culture in treating synthetic wastewater with high Chemical Oxygen Demand (COD) and varying atrazine concentration was studied. Performance of hybrid reactors with wood charcoal as adsorbent, with a dose of 10 g/l and 40 g/l, along with the microbial mass was also studied. All the reactors were operated in sequential mode with Hydraulic Retention Time (HRT) of 5 days. In all the cases, COD removal after 5 days was found to be above 81%. Initial COD was above 1000 mg/l. From a hybrid reactor COD removal after 2 days was observed to be 90%. Atrazine reduction after 5 days by microbial mass alone was 43.8%, 40% and 33.2% with an initial concentration of 0.5, 1.0 and 2.0 mg/l respectively. MLSS on all the cases were almost same. Increasing MLSS concentration by about 2 fold did not increase the atrazine removal efficiency significantly. Maximum atrazine removal was observed to be 64% from the hybrid reactor with 10 g/l of wood charcoal and 69.4% from the reactor with 40 g/l of wood charcoal. Atrazine removal from the hybrid reactors after 15 days were observed to be 35.7% and 38.7%, which showed that the higher dose of wood charcoal in hybrid reactor did not improve the atrazine removal efficiency significantly. Specific methanogenic activity test showed no inhibitory effect of atrazine on methane producing bacteria. The performance of anaerobic microorganisms in removing atrazine with no external carbon source and inorganic nitrogen source was studied in batch mode. With an initial concentration of 1.0 mg/l, reduction of atrazine by the anaerobic microorganisms in absence of external carbon source after 35 days was observed to be 61.8% where as in absence of external carbon and inorganic nitrogen source the reduction was only 44.2% after 150 days. Volatilization loss of atrazine was observed to be insignificant.

Spectrofluorimetric determination of arsenic in water samples

Parts per billion (ppb) levels of arsenic can be determined by using the fluorimetric method described here. It is based on the formation of an anionic complex of arsenic(V) with benzene-1,2-diol (catechol) and subsequent formation of an ion-association complex with 3,6-bis(dimethylamino)acridine, known as acridine orange. This was extracted quantitatively in toluene. The dye is then back-extracted with acid in the aqueous layer. In a basic medium it shows a bright yellow fluorescence at a λem of 530 nm (λex, 480 nm). The fluorescence intensity is a direct measure of the arsenic(V) concentration. The calibration graph is linear in the range 4–400 ppb. Arsenic(III) was also quantified following oxidation. The method is not interfered with by phosphate. It is applicable to real samples.

Sorption of anionic surfactants on a fixed bed of rubber granules

The performance of a fixed-bed adsorber (FBR) column for the removal of anionic surfactants from aquatic environments has been studied. Waste tyre rubber granules were used as the adsorbent material, and sodium dodecyl sulfate, an anionic surfactant, as the adsorbate. The FBR column design parameters were evaluated using the column breakthrough data at different bed depths. The Bohert and Adams model was used with the bed depth service time approach for the design of the column. The bed efficiency obtained was 90.97%.

Sorption and desorption of lindane by wood charcoal in fixed‐bed reactor

Abstract Sorption and desorption of lindane (y‐HCH) by wood charcoal (WC) and wood charcoal treated by 1N HNO3 (WCT) in fixed‐bed reactor (FBR) were investigated in this study. WCT revealed a better performance than WC, in removing lindane in FBR. The breakthrough of lindane was significantly affected by the size of WCT, flow rate to the FBR, and depth of WCT bed. The removal of lindane in the presence of mixture of other pesticides was considerably reduced. The design parameters for FBR were calculated based on the bed‐depth service time (BDST) approach. Many parameters Viz. depth of sorption zone, velocity of sorption, sorbent use rate, critical bed‐depth, bed efficiency, and service time, were determined for design of the fixed‐bed. Using the material balance principle, the characteristics of the wave‐front were evaluated and found that the wave‐front velocity is approximately equal to the sorption velocity determined from the BDST approach. Desorption studies were performed in dilute organic solvent m...

Assessment of equilibrium time and effect of co‐solutes in lindane sorption

Abstract The wood charcoal treated by 1N HNO3 (WCT) was used to remove toxic chlorinated pesticide lindane (γ‐HCH) residue from water by the sorption process. The continuously mixed batch reactors (CMBR) were used to study the effect of system parameters, such as initial sorbate concentration, sorbent size, and sorbent dose on the sorption equilibrium time of lindane by WCT. Using a rational approach an appropriate value of the equilibrium time was determined. The assessed equilibrium time from such an approach was found to be less than the value obtained by rough estimate which is commonly adopted in practice. The co‐solutes or co‐sorbates, such as DDT and pentachlorophenol (PCP) imparted a marked decrease in sorption of lindane, whereas trichlorophenol (TCP) did not affect the removal pattern. WCT showed a preferential sorption of (i) DDT > lindane > α‐HCH > β‐HCH and (ii) PCP > lindane > TCP. At a concentration ≥ 20 mg/l of fertilizers, both urea and single super phosphate (SSP) significantly affected ...

Diffusion mechanism of lindane into wood charcoal

Abstract The wood charcoal treated by 1N HNO3 (WCT) was used to remove toxic chlorinated pesticide lindane (y‐HCH) residue from water by the sorption process. Using a simple first order reversible kinetics constants and half time equations, the film and pore diffusion coefficients were determined. Film diffusion was found to be rate limiting step in sorbing lindane by WCT. This was further authenticated by kinetics studies at different initial sorbate concentrations, different sorbent sizes, and different agitation speeds besides interruption test. A pore diffusion model was used to fit the data of kinetics in continuously mixed batch reactors (CMBR), and the tortuosity, external resistance, and surface diffusion effects on lindane sorption by WCT were noticed. The tortuosity values of 15 to 28 were obtained for WCT‐lindane system.

Problem of arsenic in groundwater - a feasible solution

West Bengal in India and Bangladesh achieved remarkable successes in providing drinking water at low cost to the rural population through sinking of shallow tubewells in floodplain aquifers. Unfortunately arsenic contamination of shallow tubewell water in excess of the acceptable limit has become a major public health problem in both the countries. The contamination scenario in West Bengal and Bangladesh appears to be the worst detected so far worldwide, both in terms of area and population. The probable source of arsenic has been reported to be through geological formation. Thousands of people have already shown the symptoms of arsenic poisoning and several millions are at risk of arsenic contamination from drinking tubewell water. Arsenic toxicity has no known effective medicine for treatment, but drinking of arsenic–free water can help the arsenic–affected people to get rid of the symptoms of arsenic toxicity. Hence, provision of arsenic–free water is urgently needed to mitigate arsenic toxicity and protection of health and well–being of rural people living in acute arsenic problem areas of Bangladesh and India. The most commonly used technologies include oxidation, co–precipitation and adsorption onto coagulated flocs, adsorption onto sorptive media, ion exchange resin, and membrane techniques. In this chapter the above methods have been discussed along with a very low–cost adsorbent called CalSiCO developed in our laboratory at the Indian Institute of Technology, Kharagpur.