Services of Algae to the Environment

CHAND, RAI, LAL,KUMAR, HAR DARSHAN,MOHN, FRIEDER HELMUT,SOEDER, CARL JOHANNAS 한국미생물 · 생명공학회 2000 Journal of microbiology and biotechnology Vol.10 No.2

Being autotrophic, algae occupy a strategic place in the biosphere. They produce oxygen both directly and indirectly through the chloroplasts of all green plants. The chloroplasts are believed to have originated from archaic prokaryotic algae through endosymbiosis with primitive eukaryotic cells. Phytoplankton and other algae regulate the global environment not only by releasing oxygen but also by fixing carbon dioxide. They affect water quality, help in the treatment of sewage, and produce biomass. They can be used to produce hydrogen which is a clean fuel, and biodiesel, and fix N_2 for use as a biofertilizer. Some other services of algae to the environment include restoration of metal damaged ecosystems, reducing the atmospheric CO_2 load and mitigating global warming, reclamation of saline-alkaline unfertile lands, and production of dimethyl sulphide (DMS) and oxides of nitrogen (NOx) involved in the regulation of UV radiation, ozone concentration, and global warming. Algae can be valuable in understanding and resolving certain environmental issues.

Influence of Pyrolysis Conditions and Type of Resin on the Porosity of Activated Carbon Obtained From Phenolic Resins

Agarwal, Damyanti,Lal, Darshan,TripathiN, V.S.,Mathur, G.N. Korean Carbon Society 2003 Carbon Letters Vol.4 No.2

In polymer precursor based activated carbon, the structure of starting material is likely to have profound effect on the surface properties of end product. To investigate this aspect phenolic resins of different types were prepared using phenol, mcresol and formaldehyde as reactants and $Et_3N$ and $NH_4OH$ as catalyst. Out of these resins two resol resins PFR1 and CFR1 (prepared in excess of formaldehyde using $Et_3N$ as catalyst in the basic pH range) were used as raw materials for the preparation of activated carbons by both chemical and physical activation methods. In chemical activation process both the resins gave activated carbons with high surface areas i.e. 2384 and 2895 $m^2/g$, but pore size distribution in PFR1 resin calculated from Horvath-Kawazoe method, contributes mainly in micropore range i.e. 84.1~88.7 volume percent of pores was covered by micropores. Whereas CFR1 resin when activated with KOH for 2h time, a considerable amount (32.8%) of mesopores was introduced in activated carbon prepared. Physical activation with $CO_2$ leads to the formation of activated carbon with a wide range of surface area (503~1119 $m^2/g$) with both of these resins. The maximum pore volume percentage was obtained in 3-20 ${\AA}$ region by physical activation method.

Kinetic Studies on Physical and Chemical Activation of Phenolic Resin Chars

Damyanti Agarwal,Darshan Lal,V.S. Tripathi,G.N. Mathur 한국탄소학회 2003 Carbon Letters Vol.4 No.3

Granular Activated Carbon (GAC) has been proven to be an excellent material for many industrial applications. A systematic study has been carried out of the kinetics of physical as well as chemical activation of phenolic resin chars. Physical activation was carried out using CO2 and chemical activation using KOH as activating agent. There are number of factors which influence the rate of activation. The activation temperature and residence time at HTT varied in the range 550~1000℃ and ½~8 hrs respectively. Kinetic studies show that the rate of chemical activation is 10 times faster than physical activation even at much lower temperature. Above study show that the chemical activation process is suitable to prepare granular activated carbon with very high surface area i.e. 2895 m2/g in short duration of time i.e. 1 to 2 hrs at lower temperature i.e. 750℃ from phenolic resins.

Preparation and Charecterization of Bromofullerenes in New Stoichiometry

Mehrotra, Reema,Lal, Darshan,Tripathi, V.S.,Mathur, G.N. Korean Carbon Society 2003 Carbon Letters Vol.4 No.4

It is well established that halogenated fullerene derivatives act as synthetic intermediates for further substitution via replacement with nucleophlies. In the present work, systematic studies were carried out on the synthesis of bromofullerenes under different experimental conditions. The effect of reaction time on the product formed was observed. We observed the formation of new compound of bromofullerenes in a different stoichiometric ratio i.e., $C_{60}Br_{14}$; in addition to previous reported bromofullerenes in the stoichiometric ratio of $C_{60}Br_6$, $C_{60}Br_8$, and $C_{60}Br_{24}$. The new derivative of bromofullerene was isolated and well characterized by various analytical techniques like FT-IR, TGA, DSC, and elemental analysis. In this paper, detail of the synthesis and characterization of the bromofullerene prepared are described. The yields obtained were better than those reported previously.

Kinetic Studies on Physical and Chemical Activation of Phenolic Resin Chars

Agarwal, Damyanti,Lal, Darshan,Tripathi, V.S.,Mathur, G.N. Korean Carbon Society 2003 Carbon Letters Vol.4 No.3

Granular Activated Carbon (GAC) has been proven to be an excellent material for many industrial applications. A systematic study has been carried out of the kinetics of physical as well as chemical activation of phenolic resin chars. Physical activation was carried out using $CO_2$ and chemical activation using KOH as activating agent. There are number of factors which influence the rate of activation. The activation temperature and residence time at HTT varied in the range $550{\sim}1000^{\circ}C$ and $\frac{1}{2}{\sim}8$ hrs respectively. Kinetic studies show that the rate of chemical activation is 10 times faster than physical activation even at much lower temperature. Above study show that the chemical activation process is suitable to prepare granular activated carbon with very high surface area i.e.$ 2895\;m^2/g$ in short duration of time i.e. 1 to 2 hrs at lower temperature i.e. $750^{\circ}C$ from phenolic resins.

Influence of Pyrolysis Conditions and Type of Resin on the Porosity of Activated Carbon Obtained From Phenolic Resins

Damyanti Agarwal,Darshan Lal,V.S. TripathiN,G.N. Mathur 한국탄소학회 2003 Carbon Letters Vol.4 No.2

In polymer precursor based activated carbon, the structure of starting material is likely to have profound effect on the surface properties of end product. To investigate this aspect phenolic resins of different types were prepared using phenol, mcresol and formaldehyde as reactants and Et3N and NH4OH as catalyst. Out of these resins two resol resins PFR1 and CFR1 (prepared in excess of formaldehyde using Et3N as catalyst in the basic pH range) were used as raw materials for the preparation of activated carbons by both chemical and physical activation methods. In chemical activation process both the resins gave activated carbons with high surface areas i.e. 2384 and 2895 m2/g, but pore size distribution in PFR1 resin calculated from Horvath-Kawazoe method, contributes mainly in micropore range i.e. 84.1~88.7 volume percent of pores was covered by micropores. Whereas CFR1 resin when activated with KOH for 2h time, a considerable amount (32.8%) of mesopores was introduced in activated carbon prepared. Physical activation with CO2 leads to the formation of activated carbon with a wide range of surface area (503~1119 m2/g) with both of these resins. The maximum pore volume percentage was obtained in 3-20 a region by physical activation method.

Preparation and Charecerization of Bromofullerenes in New Stoichiometry

Reema Methrotra,Darshan Lal,V,S,Tripathi,G,N,mathur 한국탄소학회 2003 Carbon Letters Vol.4 No.4

Preparation and Charecterization of Bromofullerenes in New Stoichiometry

Reema Mehrotra,Darshan Lal,V.S. Tripathi,G.N. Mathur 한국탄소학회 2003 Carbon Letters Vol.4 No.4

It is well established that halogenated fullerene derivatives act as synthetic intermediates for further substitution viareplacement with nucleophlies. In the present work, systematic studies were carried out on the synthesis of bromofullerenesunder different experimental conditions. The effect of reaction time on the product formed was observed. We observed theformation of new compound of bromofullerenes in a different stoichiometric ratio i.e., C60Br14; in addition to previousreported bromofullerenes in the stoichiometric ratio of C60Br6, C60Br8, and C60Br24. The new derivative of bromofullerene wasisolated and well characterized by various analytical techniques like FT-IR, TGA, DSC, and elemental analysis. In this paper,detail of the synthesis and characterization of the bromofullerene prepared are described. The yields obtained were better thanthose reported previously.

Influence of Heating Rate and Temperature on Carbon Structure and Porosity of Activated Carbon Spheres from Resole-type Phenolic Beads

Arjun Singh,Darshan Lal 한국탄소학회 2009 Carbon Letters Vol.10 No.3

Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at 950℃ in N2 atmosphere followed by activation of the resultant char at different temperatures for 5 h in CO2 atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than 2260 m2/g and 1.63 cm3/g respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

Preparation and Characterization of Molecular Sieving Carbon by Methane and Benzene Cracking over Activated Carbon Spheres

Harish Chandra Joshi,Rajesh Kumar,Rohitashaw Kumar Singh,Darshan Lal 한국탄소학회 2007 Carbon Letters Vol.8 No.1

Molecular sieving carbon (MSC) for separating O2-N2 and CO2-CH4 has been prepared through chemical vapor deposition (CVD) of methane and benzene on activated carbon spheres (ACS) derived from polystyrene sulfonate beads. The validity of the material for assessment of molecular sieving behavior for O2-N2 and CO2-CH4 pair of gases was assessed by the kinetic adsorption of the corresponding gases at 25℃. It was observed that methane cracking on ACS lead to deposition of carbon mostly in whole length of pores rather than in pore entrance, resulting in a reduction in adsorption capacity. MSC showing good selectivity for CO2-CH4 and O2-N2 separation was obtained through benzene cracking on ACS with benzene entrantment of 0.40×10-4 g/ml at cracking temperature of 725℃ for a period of 90 minutes resulting in a selectivity of 3.31:1.00 for O2-N2 and 8.00:1.00 for CO2-CH4 pair of gases respectively.