Valorization of aquaculture waste in removal of cadmium from aqueous solution: optimization by kinetics and ANN analysis

Abstract

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.

Microstructure Analysis and Chemical and Mechanical Characterization of the Shells of Three Freshwater Snails

“…The estimated pore volume of the shell dust particles of P. globosa and B. costula were 0.043 and 0.031 cm 3 g –1 , with average pore diameters of 3.902 and 3.103 nm, respectively. The values were comparable to the published data on the shell dust of the snail B. bengalensis ( 36 ) (published as 10.143 m 2 g –1 for the surface area, 0.079 cm 3 g –1 for the pore volume, and 3.923 nm for the pore diameter). The specific surface area, pore volume, and pore diameter were determined by the Brunauer–Emmett–Teller (BET) method using a Quantachrome Autosorb automated with nitrogen gas (version 4.0).…”

“…For the experiments, the shells of the dead snails were cleared of flesh remnants, if any, while the opercula were removed and discarded. The shells used for the analysis were washed properly under running water and then sun-dried for at least 72 h. Prior to preparation of the shells for further studies, the shell weight (in mg) and shell length (in mm) were measured, 32 − 36 irrespective of the species, and recorded for analysis. The shell length and shell weight of the snails were as follows: B. bengalensis ( n = 30) shell length, range: 11.14–27.16; mean, 19.44 ± 0.91SE; shell weight, range: 49.9–898.9; mean, 291.93 ± 36.54SE; P. globosa ( n = 30) shell length, range: 22.056–63.56; mean, 43.76 ± 2.28SE; shell weight, range: 750.9–17126.6; mean 7127.31 ± 950.45SE; B. costula ( n = 30) shell length, range:15.66 ± 64.44; mean, 38.03 ± 1.67SE; shell weight, range: 98.9–3077.7; mean, 1153.13 ± 114.27SE.…”

“…The multiple uses of the molluscan shell as a biological material are recognized, which are mostly linked with mussels, clams, abalones, and oysters that are of marine origin. − In contrast, the potential of the shells of freshwater snails and mussels as biological materials are yet to be significantly explored. Although they are harvested as food resource, the efficacy of the discarded shells of freshwater snails and mussels as metal biosorbents appears to be considerably higher − in terms of metal removal and availability in nature. The shells of the freshwater snail Pomacea canaliculata is used as PVC composite materials as well as for metal bioremediation .…”

“…The shell of the snail B. bengalensis is a cost-effective biosorbent for cadmium and bears potential in bioremediation . While the shell formation is intricately guided by physical and genetic factors, the redundant chemical constituents are the calcium carbonate crystals that vary in different molluscan species. − ,− An assessment of the calcium carbonate content would also specify the quality of the shells as biological materials.…”

Snail Shells Adsorbent for Copper Removal from Aqueous Solutions and the Production of Valuable Compounds

“…Furthermore, the SSP exhibits heterogeneous surface morphology. ese results are in accordance with those found in previous studies [24,35,36].…”