The ability of the shell dust of freshwater mussel Lamellidens marginalis (MSD) to remove cadmium from the aquatic system was evaluated. The results indicate that MSD, a waste biomaterial, bears the potential to remove cadmium from contaminated water with a biosorption capacity of 18.18 mg g −1 at pH 6. At equilibrium, the adsorption data fitted to Langmuir (r 2 = 0.992) significantly more than the Freundlich equation (r 2 = 0.66). Regression analysis suggests that the biosorption kinetics followed the pseudo-second-order model (r 2 = 0.999) better than the Lagergren model (r 2 = 0.879). The possible mechanism of biosorption appeared to be ion exchanges with Fe, Al, Si, In, Co, and Ca ions together with binding of different functional groups such as −OH, −CO, −CC, and −C−C, as revealed through FTIR and EDX analyses. Although low in comparison to cadmium, the MSD-adsorbed zinc (q max = 10.64 mg g −1 ) and lead (q max = 8.06 mg g −1 ) varied in amounts, depending upon the initial metal ion concentration and biomass of the adsorbent. These observations substantiate MSD as a low cost and environment friendly biosorbent for heavy metal ion bioremediation.

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Cadmium is one of the most hazardous heavy metal concerning human health and aquatic pollution. The removal of cadmium through biosorption is a feasible option for restoration of the ecosystem health of the contaminated freshwater ecosystems. In compliance with this proposition and considering the efficiency of calcium carbonate as biosorbent, the shell dust of the economically important snail Bellamya bengalensis was tested for the removal of cadmium from aqueous medium. Following use of the flesh as a cheap source of protein, the shells of B. bengalensis made up of CaCO 3 are discarded as aquaculture waste. The biosorption was assessed through batch sorption studies along with studies to characterize the morphology and surface structures of waste shell dust. The data on the biosorption were subjected to the artificial neural network (ANN) model for optimization of the process. The biosorption process changed as functions of pH of the solution, concentration of heavy metal, biomass of the adsorbent and time of exposure. The kinetic process was well represented by pseudo second order (R 2 = 0.998), and Langmuir equilibrium (R 2 = 0.995) had better fits in the equilibrium process with 30.33 mg g −1 of maximum sorption capacity. The regression equation (R 2 = 0.948) in the ANN model supports predicted values of Cd removal satisfactorily. The normalized importance analysis in ANN predicts Cd 2+ concentration, and pH has the most influence in removal than biomass dose and time. The SEM and EDX studies show clear peaks for Cd confirming the biosorption process while the FTIR study depicts the main functional groups (-OH, C-H, C=O, C=C) responsible for the biosorption process. The study indicated that the waste shell dust can be used as an efficient, low cost, environment friendly, sustainable adsorbent for the removal of cadmium from aqueous solution.

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The metal bioadsorption potential of shell dust of the freshwater snail Melanoides tuberculata (MTSD) was evaluated under laboratory conditions using cadmium as a model metal. As bioadsorbent, MTSD exhibited a biosorption capacity of 27.03 mg g ¡1 at pH 6, indicating potential to remove cadmium from aqueous solution. The adsorption data fit more to the Langmuir (R 2 D 0.998) equation than the Freundlich (R 2 D 0.761) equation at equilibrium condition. The kinetics of biosorption followed the pseudosecond-order model (R 2 D 0.999) better than the Lagergren model (R 2 D 0.676), as was evident from the regression analysis. The presence of calcium ions appears to have facilitated ion exchange with cadmium along with the binding of different functional groups, as revealed through Fourier transform infrared (FT-IR) analysis. It is apparent from these observations that MTSD can act as low-cost and efficient bioadsorbent for cadmium bioremediation from aquatic habitats. Use of the shells of M. tuberculata for metal biosorption will promote the utility of a waste material of biological origin for bioremediation of heavy metals such as cadmium.

Butterflies have always attracted attention due to their unique colourations.  As most butterflies are highly specific in their niche utilisation, abundance of the species in a locality may advocate status of ecosystem functioning and environmental health.  In recent times, different anthropogenic activities and unscientific management of nature have resulted in a decline of butterfly communities at a rapid rate.  The objective of the present study is to study butterfly diversity in and around Midnapore Town, West Bengal, India.  A total of 82 butterfly species belonging to six families were recorded during the two years of the study period.  Of the six families Nymphalidae is the most abundant family comprising 42.54% of the total population followed by Lycaenidae (22.5%), Pieridae (19.03%), Papilionidae (8.58%), Hesperiidae (7.24%), and Riodinidae (0.11%).  Different diversity indices, Lorenz curve, Whittaker plot, and Gini index show high diversity in the butterfly community structure.  As Midnapore Town is the connecting area between the plains of Bengal and Chota Nagpur Plateau, the present study may be the baseline for further ecological, environmental, and conservation studies.

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