Ligy Philip

In this study, the potential of spent activated carbon from water purifier (Aqua Guard, India) for the removal of atrazine (2 chloro-4 ethylamino-6- isopropylamino-1, 3, 5 triazine) from wastewaters was evaluated. Different grades of spent activated carbon were prepared by various pretreatments. Based on kinetic and equilibrium study results, spent activated carbon with a grain size of 0.3-0.5 mm and washed with distilled water (designated as WAC) was selected for fixed column studies. Batch adsorption equilibrium data followed both Freundlich and Langmuir isotherm. Fixed bed adsorption column with spent activated carbon as adsorbent was used as a polishing unit for the removal of atrazine from the effluent of an upflow anaerobic sludge blanket (UASB) reactor treating atrazine bearing domestic wastewater. Growth of bacteria on the surface of WAC was observed during column study and bacterial activity enhanced the effectiveness of adsorbent on atrazine removal from wastewater.

In the present investigation, an attempt was made to develop a treatment system for the management of atrazine bearing wastewater. The system consists of an upflow anaerobic sludge blanket (UASB) reactor followed by an adsorption column using waste activated carbon as the adsorbent. The UASB reactor could remove more than 80% of organic matter and 40-50% of atrazine, irrespective of the concentration of organic matter and atrazine tried. Though low concentration of atrazine did not affect the anaerobic system, higher atrazine concentration in the range of 10-15 mg/ L had a little effect on the treatment system. The adsorption column could remove atrazine from the UASB effluent effectively. Methanol could desorb the atrazine from the adsorbent. The regenerated adsorbent retained 80% of its original capacity. The regenerant can be utilized as a pesticide. © ASCE.

Adsorption of three pharmaceuticals, namely, atenolol, ciprofloxacin and gemfibrozil using synthesized magnetic polymer clay composite was investigated in detail by conducting batch kinetic, equilibrium and desorption experiments. Optimum ratio of composite adsorbent was found to be clay: chitosan: powdered activated carbon (PAC): magnetic nano particles (MNP) as 1:0.5:0.3:0.3. Characterization studies showed the incorporation of modifiers into the clay structure. Surface area of the synthesized pellets was 94.81 m2/g with mesoporous surface. Freundlich model was able to predict the adsorption equilibrium data. Maximum adsorption capacities were estimated to be 15.6, 39.1 and 24.8 mg/g for atenolol, ciprofloxacin and gemfibrozil, respectively. The main driving force of adsorption was electrostatic interaction. The adsorbent performance was affected at lower and higher pH and by the presence of humic acid. Desorption of atenolol and ciprofloxacin were significantly higher in acid and alkaline solution whereas gemfibrozil was desorbed upto 70% in methanol. Magnetically separable clay composite was found to be a suitable adsorbent for removing pharmaceuticals from water.

Arsenicosis was recognized over 104 years ago. Elevated arsenic (As) concentrations in water is faced by about 200 million people worldwide and has become one of the biggest challenges in the context of water purification. Providing sustainable and affordable solutions to tackle this menace is a need of the hour. Adsorption on advanced materials is increasingly being recognized as a potential solution. Here, we report various functionalized microcellulose-reinforced 2-line ferrihydrite composites which show outstanding As(III) and As(V) adsorption capacities. Green synthesis of the composite yields granular media with high mechanical strength which show faster adsorption kinetics in a wide pH range, irrespective of the presence of other interfering ions in water. The composites and their interaction with As(III) and As(V) were studied by XRD, HRTEM, SEM, XPS, Raman, TG, and IR spectroscopy. Performance of the media in the form of cartridge reaffirms its utility for point-of-use water purification. We show that cellulose microstructures are more efficient than corresponding nanostructures for the purpose of arsenic remediation. We have also performed an evaluation of several sustainability metrics to understand the "greenness" of the composite and its manufacturing process.

In this study, adsorption potential of a new sorbent manganese-oxide-coated alumina (MOCA) was investigated for defluoridation of drinking water using batch and continuous mode experiments. The effects of different parameters such as pH, initial fluoride concentration and co-existing ions (usually present in groundwater sample) were studied to understand the adsorption behavior of the sorbent under various conditions. Optimum removal of fluoride ions occurred in a pH range of 4-7. Results of the present study indicate that fluoride adsorption rate and adsorption capacity of MOCA are far superior to that of activated alumina (AA), which was used as the base material for MOCA preparation. The MOCA can be effectively regenerated using 2.5% NaOH as eluent. The Langmuir equilibrium model was found to be suitable for describing the fluoride sorption on AA and MOCA. The maximum fluoride uptake capacity for MOCA and AA was found to be 2.85 and 1.08 mg g-1, respectively. The kinetic results showed that the fluoride sorption to MOCA followed pseudo-second-order kinetics with a correlation coefficient greater than 0.98. The fluoride sorption capacity at breakthrough point for both the adsorbents was greatly influenced by bed depth. A bed depth service time (BDST) approach was adopted to describe the continuous flow system. The batch and column studies demonstrated the superiority of MOCA over AA in removing fluoride from the drinking water system. © 2006 Elsevier Ltd. All rights reserved.

This paper describes the arsenite [As(III)] removal performance of manganese oxide-coated-alumina (MOCA) and its interaction with As(III) in drinking water. MOCA was characterized by XRD, SEM, EDAX, gas adsorption porosimetry, and point of zero charge (pHpzc) measurements. Raman spectroscopy coupled with sorption experiments were carried out to understand the As(III) interaction with MOCA. As(III) sorption onto MOCA was pH dependent and the optimum removal was observed between a pH of 4 and 7.5. The Sips isotherm model described the experimental equilibrium data well and the predicted maximum As(III) sorption capacity was 42.48 mg g-1, which is considerably higher than that of activated alumina (20.78 mg g-1). The sorption kinetics followed a pseudo-second-order equation. Based on sorption and spectroscopic measurements, the mechanism of As(III) removal by MOCA was found to be a two-step process, i.e. oxidation of As(III) to arsenate (As(V)) and retention of As(V) on MOCA surface, with As(V) forming an inner surface complex with MOCA. The results of this study indicated that MOCA is a promising alternative sorbent for As(III) removal from drinking water. © 2009 Elsevier B.V. All rights reserved.

This study investigated the adsorption behavior and sustainability of biochar to remove four pharmaceutical and personal care products (PPCPs). The biochar (PEBC) was prepared via slow pyrolysis of empty palm bunch (PEB) at three temperatures (250-750 °C). To improve the adsorption capacity further, PEBC450 was acid treated with H2SO4 to develop PEBC450-A. The adsorption behavior of target pollutants (methyl paraben (MPB), carbamazepine (CZP), ibuprofen (IBP), and triclosan (TCS)) onto PEBC450-A was studied in batch experiments, and phenomenological and statistical models were applied to understand the sorption mechanism. Results demonstrated that the adsorption system was able to achieve fast equilibrium (in 4 h), with maximum adsorption capacities as 60.2 mg/g (MPB), 51.7 mg/g (CZP), 38.8 mg/g (IBP), 35.4 mg/g (TCS). The modeling results showed heterogeneous adsorption of PPCPs involving the participation of multiple functional groups in parallel and non-parallel orientations. The mass transfer kinetic models identified the internal mass transfer resistance as the rate-limiting step. The PPCPs adsorption was significantly affected by the change in solution pH and the presence of humic acid. However, no substantial change in PPCPs removal was observed in the presence of co-existing ions and different ionic strengths. In multi-pollutant systems and real water samples, PEBC450-A maintained more than 75% removal of target pollutants, indicating the developed material as a promising adsorbent for wastewater treatment. The sorption mechanism was found to be channel diffusion, hydrogen bonding, n-πand π-πinteractions, and van der Waals force. The comparative life cycle assessment of PEBC450-A and commercial activated carbon showed that the total impact contribution of PEBC450-A was 20 times less than commercial activated carbon. The overall finding makes PEBC450-A a low-cost and sustainable adsorbent for water treatment.

In the present study, the systematic approach to access the fate and predominant pathway of selected surfactants and personal care products (sodium dodecyl sulphate, propylene glycol and trimethyl amine) in hydroponic mesocosms, biodegradation and adsorption by soils are described. The overall objective of the study is to determine the kinetics of depletion (from solution) and uptake of pollutants by plants (Phragmites australis) growing hydroponically, biodegradation kinetics of target pollutants under aerobic, anoxic and anaerobic conditions and determine the adsorption kinetics of three target pollutants in four different soils. The potential for translocation from root to shoot, bio-concentration and risk assessment of these three surfactants and personal care products were also assessed. After 35 days of hydroponics experiment, nearly 20% of the sodium dodecyl sulphate was removed from the nutrient solution followed by propylene glycol (19.2%) and trimethyl amine (14.5%). The photodegradation played a very minor role in the pollutant degradation. Amongst the three target pollutants trimethyl amine was more (8.16%) taken up by the plants followed by propylene glycol (7.2%) and sodium dodecyl sulphate (5.2%). It was also found that all the three pollutants are biodegraded by the enriched microbes within 3 days, with higher rate observed for propylene glycol. Sodium dodecyl sulphate found to be a recalcitrant was maximum (58.2%) sorbed to the soil surface followed by trimethyl amine and propylene glycol. Hence, a treatment system that combines the adsorption, biodegradation and plant uptake will be the viable option for elimination the surfactants and personal care products contaminated water.