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ABSTRACT:The biosorption of chromium (VI) ions from aqueous solutions by two adsorbents viz. mango and neem sawdust was studied under a batch mode. An initial pH of 2.0 was most favorable for chromium (VI) removal by both the adsorbents. The results obtained for the final concentration of chromium (VI) and chromium (III) at a pH range of 2-8 indicated that a combined effect of biosorption and reduction was involved in the chromium (VI) removal specially when the pH value is lower than 3. The maximum loading capacity was calculated from adsorption isotherms by applying the Langmuir model and found to be higher for neem sawdust (58.82 mg/g). Evaluation of experimental data in terms of biosorption kinetics showed that the biosorption of chromium (VI) by neem sawdust followed pseudo second-order kinetics. Therefore, the rate limiting step may be chemical sorption or chemisorption. The efficiency of this process was examined in using tannery wastewater contaminated with chromium (VI) ions in column mode. ). The raw tannery wastewater sample collected from a common effluent treatment plant (CETP) located in Vaniyambadi, Vellore Dt., Tamil Nadu, India was analyzed promptly for determining the physicochemical characteristics using standard analytical methods (APHA, 1998). The characteristics of the wastewater were: color: black, pH: 6.1, TDS: 7794 mg/L, TSS: 4896 mg/L, sulphates: 878 mg/L, chlorides: 2927 mg/L and nitrate: 9.8 mg/L. The concentration of chromium (VI) in wastewater was detected using UV spectrophotometer: 94 mg/L and pH was adjusted to 2.0 using 0.1 N HNO 3 . The wastewater was then fed through a glass column (3 cm i.d. and 10cm long) packed with 20 g of the biosorbent neem sawdust at a flow rate of 5.0 mL/min controlled by a peristaltic pump. After treatment, the samples collected from the exit were analyzed for chromium (VI) concentrations. The wastewater was treated till the values reached to satisfy the Central Pollution Control Board (CPCB) standards (Cr (VI) -0.1 mg/L) (CPCB, 1998). Keywords RESULTS AND DISCUSSION Effect of pH on sorptionEarlier studies on heavy metal biosorption have shown that solution pH is the single most important parameter affecting the biosorption process (Chen et al., 2002). In order to establish the effect of pH on the biosorption of chromium (VI) ions, batch sorption studies at different pH values were conducted in the range of 2.0 to 8.0. Fig. 1 reveals that biosorption capacity of Cr (VI) ions is maximum at pH 2.0 and significantly decreases with increase in pH values upto 8.0. At pH 2 and 8 corresponding uptake yield values were found to be 80.1% and 7.6 % for neem sawdust, 60 % and 6.3 % for mango sawdust, respectively.At lower pH, the biosorbent is positively charged due to protonation and dichromate ion exists as anion leading to an electrostatic attraction between them (Boddu et al., 2003). Thus the uptake of chromium (VI) increased markedly with decreasing pH. A sharp decrease in adsorption above pH 4 may be due to occupation of the adsorption sites by anionic spe...

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Tragia involucrata Linn. a perennial herb, is a potential source of phytoconstituents like terpenoids, sterols, phenols and carbohydrates. The plant is used as traditional medicine for treatment of skin eruption, diabetes, and cephelagia in many regions. Rationale of the present study was to carry out phytochemical screening and examine the in-vitro α-amylase inhibitory role of Tragia involucrata Linn. extracts. The α-amylase inhibitory potential of extracts was studied by dinitrosalicylic acid (DNS) method and it was found that aqueous extract (TI-A), ethyl acetate extract (TI-EA) and chloroform extract (TI-C) with increasing concentration restrain effective α-amylase enzyme inhibitory activity.

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