| 1. |
- Avila, Marta, et al.
(författare)
-
Surface functionalized nanofibers for the removal of chromium(VI) from aqueous solutions
- 2014
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 245, s. 201-209
-
Tidskriftsartikel (refereegranskat)abstract
- Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (> 90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.
|
|
| 2. |
- Azis, Muhammad Mufti, 1983, et al.
(författare)
-
Microkinetic modeling of H2-assisted NO oxidation over Ag-Al2O3
- 2013
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 221, s. 382-397
-
Tidskriftsartikel (refereegranskat)abstract
- A microkinetic model has been assembled to investigate the mechanism for NO oxidation over a monolith-supported Ag–Al2O3 catalyst both in the presence and absence of H2. The effect of H2 examined in the kinetic model was to reduce self inhibiting surface nitrate species on active silver sites. A reduced factorial design of inlet experimental conditions was used to generate transient experimental data. The kinetic model was developed based on a single channel reactor model which accounted for mass and heat transfer between gas and catalyst washcoat as well as mass transport resistance in the washcoat. In general, the modeling results could reproduce the transient experimental data well with correct levels of outlet concentrations and time scales for transient responses. It was found that the effect of increased NO and NO2 inlet concentration had a negative correlation with the NO oxidation conversion, which in the model was considered related to the formation of nitrate surface species. In addition, the model in agreement with experiments, clearly showed that H2 promoted the NO oxidation mainly at low temperature and this effect tended to decrease at elevated temperatures. When H2 was present in the feed, the kinetic model showed that H2 was consumed rapidly in the front part of the monolith. This was also seen in the experiments where in all cases H2 was entirely consumed. The rapid reaction of H2 along with resulting transport limitations indicated that the H2 promotion of the NO oxidation reaction may have been isolated to only a portion of the catalyst.
|
|
| 3. |
- Bhatnagar, Amit, et al.
(författare)
-
A review of emerging adsorbents for nitrate removal from water
- 2011
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 168:2, s. 493-504
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrate, due to its high water solubility, is possibly the most widespread groundwater contaminant in the world, imposing a serious threat to human health and contributing to eutrophication. Among several treatment technologies applied for nitrate removal, adsorption has been explored widely and offers satisfactory results especially with mineral-based and/or surface modified adsorbents. In this review, an extensive list of various sorbents from the literature has been compiled and their adsorption capacities for nitrate removal as available in the literature are presented along with highlighting and discussing the key advancement on the preparation of novel adsorbents tested for nitrate removal.
|
|
| 4. |
- Bhatnagar, Amit, et al.
(författare)
-
An overview of the modification methods of activated carbon for its water treatment applications
- 2013
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 219, s. 499-511
-
Forskningsöversikt (refereegranskat)abstract
- Activated carbon has been recognized as one of the oldest and widely used adsorbent for the water and wastewater treatment for removing organic and inorganic pollutants. The application of activated carbon in adsorption process is mainly depends on the surface chemistry and pore structure of porous carbons. The method of activation and the nature of precursor used greatly influences surface functional groups and pore structure of the activated carbon. Therefore, the main focus of researchers is to develop or modifies the activation/treatment techniques in an optimal manner using appropriate precursors for specific pollutants. In recent years, emphasis is given to prepare the surface modified carbons using different procedures to enhance the potential of activated carbon for specific contaminants. Various methods such as, acid treatment, base treatment, impregnation treatment, ozone treatment, surfactant treatment, plasma treatment and microwave treatment have been studied to develop surface modified activated carbons. In this paper, these modification methods have been reviewed and the potential of surface modified activated carbons towards water treatment has been discussed. This review article is aimed at providing precise information on efforts made by various researchers in the field of surface modification of activated carbon for water pollution control. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Bhatnagar, Amit, et al.
(författare)
-
Fluoride removal from water by adsorption : A review
- 2011
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 171:3, s. 811-840
-
Tidskriftsartikel (refereegranskat)abstract
- Fluoride contamination in drinking water due to natural and anthropogenic activities has been recognized as one of the major problems worldwide imposing a serious threat to human health. Among several treatment technologies applied for fluoride removal, adsorption process has been explored widely and offers satisfactory results especially with mineral-based and/or surface modified adsorbents. In this review, an extensive list of various adsorbents from literature has been compiled and their adsorption capacities under various conditions (pH, initial fluoride concentration, temperature, contact time, adsorbent surface charge, etc.) for fluoride removal as available in the literature are presented along with highlighting and discussing the key advancement on the preparation of novel adsorbents tested so far for fluoride removal. It is evident from the literature survey that various adsorbents have shown good potential for the removal of fluoride. However, still there is a need to find out the practical utility of such developed adsorbents on a commercial scale, leading to the improvement of pollution control.
|
|
| 6. |
- Bhatnagar, Amit, et al.
(författare)
-
Nitrate removal from water by nano-alumina : Characterization and sorption studies
- 2010
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 163:3, s. 317-323
-
Tidskriftsartikel (refereegranskat)abstract
- The present study was conducted to evaluate the feasibility of nano-alumina for nitrate removal from aqueous solutions. The nature and morphology of sorbent was characterized by XRD, FTIR, BET and SEM analysis. Batch adsorption studies were performed as a function of contact time, initial nitrate concentration, temperature, pH and influence of other interfering anions. Nitrate sorption kinetics was well fitted by pseudo-second-order kinetic model. The maximum sorption capacity of nano-alumina for nitrate removal was found to be ca. 4.0 mg g(-1) at 25 +/- 2 degrees C. Maximum nitrate removal occurred at equilibrium pH ca. 4.4. The nitrate sorption has been well explained using Langmuir isotherm model. Results from this study demonstrated the potential utility of nano-alumina for nitrate removal from water.
|
|
| 7. |
- Bhatnagar, Amit, et al.
(författare)
-
Optimization of nickel biosorption by chemically modified brown macroalgae (Pelvetia canaliculata)
- 2012
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 193, s. 256-266
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work, various forms of algae Pelvetia canaliculata were prepared by different chemical modifications, in order to get the best form of algae for the maximum uptake of nickel. Potentiometric titration revealed that the carboxyl groups were more abundant (3.9 mmol/g) as compared to hydroxyl groups (2.0 mmol/g) on the biosorbent surface. Fourier transform infrared (FUR) analysis of algae was done to identify the role of different functional groups present on algae surface during nickel biosorption. The protonated algae showed least sorption of nickel suggesting that after acid treatment, some of the binding sites were destroyed. Among the various forms of prepared algae. Na-algae prepared directly from raw algae (without protonation) showed highest uptake of nickel. The release of sodium ions during the uptake of nickel ions has shown that the current biosorption mechanism involves ion-exchange being a stoichiometrical ratio of 2:1 between sodium and nickel ions.
|
|
| 8. |
- Bhatnagar, Amit, et al.
(författare)
-
Utilization of agro-industrial and municipal waste materials as potential adsorbents for water treatment- A Review
- 2010
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 157:2-3, s. 277-296
-
Tidskriftsartikel (refereegranskat)abstract
- Adsorption process has been proven one of the best water treatment technologies around the world and activated carbon is undoubtedly considered as universal adsorbent for the removal of diverse types of pollutants from water. However, widespread use of commercial activated carbon is sometimes restricted due to its higher costs. Attempts have been made to develop inexpensive adsorbents utilizing numerous agro-industrial and municipal waste materials. Use of waste materials as low-cost adsorbents is attractive due to their contribution in the reduction of costs for waste disposal, therefore contributing to environmental protection. In this review, an extensive list of low-cost adsorbents (prepared by utilizing different types of waste materials) from vast literature has been compiled and their adsorption capacities for various aquatic pollutants as available in the literature are presented. It is evident from the literature survey that various low-cost adsorbents have shown good potential for the removal of various aquatic pollutants. However, there are few issues and drawbacks on the use of low-cost adsorbents in water treatment that have been discussed in this paper. Additionally, more research is needed to find the practical utility of low-cost adsorbents on commercial scale.
|
|
| 9. |
- Bhatnagar, Amit, et al.
(författare)
-
Valorisation of marine Pelvetia canaliculata Ochrophyta for separation and recovery of nickel from water: equilibrium and kinetics modeling on Na-loaded algae
- 2012
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 200, s. 365-372
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, biosorption of Ni2+ by Na-loaded (raw algae treated with NaCl), algae Pelvetia canaliculata Ochrophyta, was studied in a batch system. Kinetics and equilibrium experiments were conducted at different pH values (2.0, 3.0 and 4.0). The metal uptake capacity decreased by decreasing the solution pH, suggesting that competition exists between hydrogen ions, present in high concentrations at low pH values, and metal ions. An ion-exchange model, considering two different binding sites, sulfonic and carboxylic groups, was developed to describe equilibrium data. A mass transfer model, considering intraparticle resistance was also developed to describe kinetics in a batch system. The release of sodium ions during the uptake of nickel ions revealed that the biosorption mechanism involved ion-exchange between sodium and nickel ions with a stoichiometrical ratio of 2:1. Nickel showed higher affinity to the sulfonic groups than for carboxylic ones of algae biomass. Kinetic results show that hydrogen ions diffuse faster as compared to nickel and sodium ions. The maximum uptake capacity of Na-loaded algae, P. canaliculata, for Ni2+ was found to be ca. 100 mg/g at pH 4.0.
|
|
| 10. |
- Brandin, Jan, 1958-, et al.
(författare)
-
High-temperature and high concentration SCR of NO with NH3 : application in a CCS process for removal of carbon dioxide
- 2012
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 191, s. 218-227
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates several commercial selective catalytic reduction (SCR) catalysts (A–E) for application in a high-temperature (approximately 525 °C) and high-concentration (5000 ppm NO) system in combination with CO2 capture. The suggested process for removing high concentrations of NOx seems plausible and autothermal operation is possible for very high NO concentrations. A key property of the catalyst in this system is its thermal stability. This was tested and modelled with the general power law model using second-order decay of the BET surface area with time. Most of the materials did not have very high thermal stability. The zeolite-based materials could likely be used, but they too need improved stability. The SCR activity and the possible formation of the by-product N2O were determined by measurement in a fixed-bed reactor at 300–525 °C. All materials displayed sufficiently high activity for a designed 96% conversion in the twin-bed SCR reactor system proposed. The amount of catalyst needed varied considerably and was much higher for the zeolithic materials. The formation of N2O increased with temperature for almost all materials except the zeolithic ones. The selectivity to N2 production at 525 °C was 98.6% for the best material and 95.7% for the worst with 1000 ppm NOx in the inlet; at 5000 ppm NOx, the values were much better, i.e., 98.3 and 99.9%, respectively.
|
|
