M. Ajmal

ROLE OF SAWDUST IN THE REMOVAL OF COPPER (II) FROM INDUSTRIAL WASTES

Abstract Sawdust, an inexpensive material has been utilised as an adsorbent for the removal of Cu(II) from waste water for their safe disposal. The effects of contact time, pH, concentration, temperature, dose, particle size of the adsorbent and salinity on the removal of Cu(II) have been studied. The equilibrium nature of copper(II) adsorption at different temperature (30–50°C) has been described by the Freundlich and Langmuir isotherm and a tentative mechanism has been proposed. The thermodynamic parameters like free energy, entropy and enthalpy changes for the adsorption of Cu(II) have also been computed and discussed. The kinetics and the factors controlling the adsorption process have also been studied.

Dithiobiurets: a novel class of acid corrosion inhibitors for mild steel

The corrosion inhibition behaviour of some substituted dithiobiurets, namely, -1,5-diphenyl-2,4-dithiobiuret (DPDTB), 1-tolyl-5-phenyl-2,4-dithiobiuret (TPDTB), 1-anisidyl-5-phenyl-2,4-dithiobiuret (APDTB), 1-chorophenyl-5-diphenyl-2,4-dithiobiuret (CPDTB) were studied in 1 to 5 M HCl on mild steel. The characteristics of these compounds are explained in terms of factors such as inhibitor concentration, acid concentration, temperature, immersion time and molecular structure. Potentiodynamic polarization and a.c. impedance techniques were used to investigate the inhibition mechanism. Among the compounds studied APDTB exhibited the best performance giving more than 98% inhibition efficiency (IE) in HCl solutions. DPDTB and CPDTB were found to reduce hydrogen permeation through mild steel in HCl solutions. The adsorption of APDTB was also confirmed by Auger electron spectroscopy (AES).

Influence of substituted benzothiazoles on corrosion in acid solution

Compounds such as 2-aminobenzothiazole (ABT), 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methyl benzothiazole (AMEBT) and 2-amino-6-methoxy benzothiazole (AMEOBT) have been synthesized and their inhibitive action on the corrosion of mild steel in 1 m HCl has been evaluated using weight loss, potentiodynamic polarization studies and hydrogen permeation measurements. Determination of inhibition efficiency in the presence of these compounds at different temperatures clearly indicates that ACLBT shows the best performance, even at a temperature as high as 60°C. Potentiodynamic polarization studies reveal the fact that ABT and its derivatives act as cathodic inhibitors. All these compounds are found to reduce the permeation of hydrogen through mild steel in HCl solution. The adsorption of these compounds on mild steel from HCl solutions obeys Temkins adsorption isotherm. The adsorption of 2-amino benzothiazole on the mild steel has been substantiated by Auger electron spectroscopy.

Heavy metals: leaching from glazed surfaces of tea mugs

Heavy metals (zinc, lead, cadmium, iron, chromium, copper, manganese, nickel and cobalt) were found to leach from the glazed surfaces of tea mugs collected from 13 different pottery units of Khurja (U.P.) and one each from Ghaziabad (U.P.) and Calcutta (West Bengal) determined under different conditions. The leachates used were: tea at 80 degrees C, orange juice at room temperature and 4% acetic acid at room temperature, 40 degrees C and 60 degrees C, respectively. The volume (capacity) of mugs ranged between 200 and 250 ml. The duration for leaching was 24 h in each case without stirring. The concentrations of metals leached in tea at 80 degrees C were found in the range (in microgram/l): Zn, 236-730; Fe, 98-925; Cr, 62-119; Cu, 63-299; Mn, 710-2670; and Ni, 70-80 micrograms/l. The concentrations of metals leached in orange juice at room temperature were in the range (in microgram/l): Zn, 393-1262; Cd, 25-349; Fe, 122-342; Cr, 66-945; Cu, 135-853; Mn, 166-424; and Ni, 70-134 micrograms/l. The concentrations of heavy metals extracted by 4% acetic acid at room temperature were found in the range (in microgram/l): Zn, 18-192; Fe, 143-372; Cu, 51-190; and Mn, 0-48 micrograms/l; at 40 degrees C (in microgram/l): Zn, 118-837; Fe, 124-639; Cu, 230-722; and Mn, 30-63 micrograms/l and at 60 degrees: Zn, 33-900; Fe, 83-576; Cu, 90-685; and Mn, 43-778 micrograms/l, respectively.

Thioamidines as novel class of corrosion inhibitors

Abstract Four nitrogen substituted thiobisformamidines – phenyl thiobisformamidines (PTBF), tolyl thiobisformamidines (TTBF), anisidyl thiobisformamidines (ATBF), and 4-chlorophenyl thiobisformamidines (CPTBF) – were synthesised and their corrosion inhibiting behaviour for mild steel in 1M, 3M, and 5M HCl was studied. The optimum concentration of these compounds for maximum inhibition efficiency was determined by weight loss methods. All the investigated thiobisformamidines gave more than 95% inhibition in the presence of 1M HCl, and CPTBF showed the best inhibition efficiency (98% in 5M HCl). Potentiodynamic polarisation studies revealed that all the tested compounds are of mixed inhibitor type. The adsorption of these compounds from the acid solution obeyed Temkins adsorption isotherm. All the inhibitors were able to reduce hydrogen permeation through the steel surface and their performance was enhanced by the addition of iodide ions. Electron impedance spectroscopic studies were also carried out in or...

Technical note Influence of molecular structure of substituted benzothiazoles on corrosion inhibition and hydrogen permeation through mild steel in sulphuric acid

Abstract Aminobenzothiazole and three of its 6-substituted derivatives, namely 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methoxybenzothiazole, and 2-amino-6-methylbenzothiazole, were synthesised and their inhibition of the corrosion of mild steel in 0·5M H2S04 was investigated by weight loss and some electrochemical techniques. Inhibition efficiencies of various concentrations of these compounds were determined at temperatures in the range 35–60°C. Of the four compounds, ACLBT showed the best performance, giving an inhibition efficiency as high as 97%, even at a very low concentration and at a temperature of 60°C. Potentiodynamic polarisation studies indicated that all four compounds acted predominantly as cathodic inhibitors, with adsorption from H2S04 solutions on mild steel surfaces obeying Temkins adsorption isotherm. All of the inhibitors were able to reduce hydrogen permeation through the steel surface and performance was enhanced by the addition of iodide ions. Auger electron spectroscopy a...

Gas chromatography : Mass spectrometric analysis of four polluted river waters for phenolic and organic compounds

Forty-four water samples from eleven sampling points were collected from four highly polluted rivers of northern India once in each four seasons during 1988–1989. The samples were analyzed for phenol, chlorophenols, a few bromophenols and other organics. Phenol was found to be absent in all the analyzed samples. Trichlorophenol and pentachlorophenol were frequently detected. Comparatively, the Ganges river was most polluted at Kannauj followed by Narora, Kachala and Fatehgarh. Maximum phenols were found at Mathura downstream of the Yamuna river followed by Mathura upstream, Okhla, ITO and none at Wazirabad. No phenols were detected in the water of the rivers Hindon and Kali at Ghaziabad and Aligarh, respectively. Some other organic pollutants were also identified by their mass spectra and supported by data from the computerized library, but, not quantified.

Effect of industrial dairy processing effluent on soil and crop plants

Abstract The physico-chemical characteristics of Glaxo Laboratories (India) Ltd effluent (GLLE), and the effects of its discharge directly on fertile soil and indirectly on kidney bean Phaseolus aureus and pearl millet Pennisetum typhoides crops for 6 weeks, were evaluated. The GLLE was slightly alkaline and had high BOD and COD due to the presence of large amounts of solids. It was rich in bicarbonates and calcium. GLLE was found to be responsible for altering the chemical composition of the soil. Soil irrigated with GLLE showed an increase in pH, organic matter, calcium carbonate content, water-soluble salts, cation exchange capacity, electrical conductivity, nitrogen and phosphorus. Potassium decreased, probably due to it being leached to the lower layers of the soil. The effects of undiluted effluent and of effluent diluted to 75%, 50% and 25%, using water irrigation as a control, on the germination and growth of kidney bean and pearl millet were monitored. The undiluted GLLE restricted the germination of kidney bean to some extent while that of pearl millet was enhanced. 100% GLLE retarded the height of plants of both crops whilst 25% effluent in kidney bean, and 75% effluent in pearl millet, enhanced it considerably.

Microbial uptake of cadmium and its effects on the biochemical oxygen demand at various temperatures

Abstract Uptake of cadmium by microbes at different temperatures has been studied at pH 7. Glycine was used as a source of carbon for microorganisms in the BOD bottle at 20, 30, 40 and 50°C with varying concentrations of cadmium: control 0.0437, 0.437, 0.875 and 1.31 mg 1 −1 in each set. The influence of temperatures on the toxic effects of cadmium has been studied with respect to rate constant (k) and ultimate biochemical oxygen demand which were calculated from BOD data using Thomas Graphical method. Consumed cadmium mg 1 −1 was determined after eight days and it varied from 14.04 to 32.40% at four temperatures. Highest consumption of Cd was noted in the set at 30 and 40°C and lowest at 50°C.

Determination of microquantities of mercury(II) with preliminary thin-layer chromatographic separation from mercury(I), lead(II), nickel(II), and copper(II) on acid-treated silica gel layers: recovery of mercury(II) from river waters and industrial wastewaters

Thin-layer chromatography in combination with spectrophotometry has been applied for the separation and estimation of Hg(II) using silica gel layers impregnated with 2% oxalic acid as stationary phase with an ethyl acetate:acetone:formic acid:water (8:7:4:1) solvent system. Separation of Hg(II) from Hg(I) and of Th4+ from UO22+ is not affected by the presence of common anions in the sample solution. Hg(II) has been successfully separated from Ni(II), Cu(II), and Pb(II) over a wide range of pH (0.5–7.0) of sample solution. An attempt has been made to recover Hg(II) from rivers and industrial wastewaters.