Wide Range Of Initial pH Research Articles

Removal of Zinc from Aqueous Solutions Using Bagasse Fly Ash − a Low Cost Adsorbent

Bagasse fly ash, a sugar industry waste, has been converted into an inexpensive and efficient adsorbent. The product obtained has been characterized and utilized for the removal of zinc from aqueous solutions over a wide range of initial metal ion concentration (3.06 × 10-4 to 3.06 × 10-3 M), contact time (24 h), adsorbent dose (5−20 g L-1), and pH (1.0−6.0). The removal of Zn2+ is 100% at low concentrations, whereas it is 60−65% at higher concentrations at an optimum pH of 4.0, using 10 g L-1 of adsorbent in 6−8 h of equilibration time. The uptake decreases with a rise in temperature indicating the process to be exothermic in nature. Kinetic studies have been performed to understand the mechanism of adsorption. The removal takes place through film diffusion mechanism at lower concentrations (≤1.84 × 10-3 M) and by particle diffusion at higher concentrations (≥ 3.06 × 10-3 M).

Scaling of Small-Angle Neutron Scattering Intensities from Gelling Colloidal Silica

Small-angle neutron scattering data, taken as a function of time from initiation of gelation in colloidal silica suspensions, with silica mass fractions ranging from 15 to 30%, are presented. Over a wide range of initial pH, the measured structure factor S(q) contains a low angle peak that, as time progresses, grows in height and moves to lower wave vectors q. Sometime after the gels have set, this peak stops growing, marking the end of the reaction. The data scale according to the relation, S(q,t)~\(q_m^{-d_f}\)(t)(q/qm(t))\(\tilde S\), where qm(t) is the wave-vector location of the low angle peak as a function of time t from initiation, df is a fractal dimension, and \(\tilde S\) is a characteristic structure function. The exponent df is insensitive to the silica mass fraction but that the form of \(\tilde S\) is mass fraction dependent.

Production and Characterization of Keratinolytic Protease of Bacillus licheniformis MZK-03 Grown on Feather Mill

Keratinolytic protease is an inducible specific proteolytic enzyme, which is produced by Bacillus licheniformis MZK-03 in presence of keratin (feather mill) as sole carbon and nitrogen source in growth medium. Maximum level of keratinolytic protease was produced after 42 h at 37°C over a wide range of initial pH (5.0 to 12.0) under continuous agitation (200 rpm). Keratinolytic protease worked best at 37°C and at pH 8.5. The enzyme was quite stable over a wide range of pH (7.0 to 11.0) but activity dropped drastically beyond this level (enzyme activity dropped to 8.8% and 19.3% at pH 6.5 and 12.0, respectively). Half-life of keratinolytic protease at 70° and 60°C were found to be 3 and 7 min respectively. The enzyme showed highest stability at 40°C (>90% after 3 h). The half-life at 4°C was 34 days. The presence of metal ions (5 mM) like Mg2+, Mn2+, Ca2+ and K+ had no remarkable effect on the keratinolytic protease activity but the activity decreased in presence of Hg2+ and Cu2+. The enzyme may belong to serine protease group as it is inhibited by serine protease inhibitor phenyl methyl sulphonyl fluoride (PMSF). The enzyme is as compatible as other commercially available enzymes used in leather industry with tannery chemicals. It was completely incompatible with Na2S and CaO for their high alkalinity (pH >13.0), which was also observed for other commercial enzymes except the commercial enzyme supplemented with ammonium sulphate. Keywords: Bacillus licheniformis MZK-03, Keratinolytic protease, Keratin, Production, CharacterizationDOI: http://dx.doi.org/10.3329/bjm.v24i1.1239 Bangladesh J Microbiol, Volume 24, Number 1, June 2007, pp 57-61