ABSTRACT
Temperature Stability and Ph Stability of AIP ...................................... 128 9.2.2.2 Scanning Electron Microscopy (SEM) and Energy Dispersive
X-Ray Spectrometry (EDS) .................................................................. 128 9.2.3 Removal of Cadmium (II) using AIP..................................................... 128 9.2.3.1 Kinetics Study .......................................................................... 128 9.2.3.2 Equilibrium Study .................................................................... 128 9.2.3.3 Determination of Optimum Condition for Removal of
Cadmium (II) By Aip using Response Surface Methodology .............. 129 9.2.4 Recovery of Cadmium (II) .................................................................... 130 9.3 Discussion and Results .................................................................................... 130 9.3.1 Immobilization of Papain ...................................................................... 130 9.3.2 Characterization of Aip .......................................................................... 130 9.3.2.1 Determination of Temperature Optima, pH Optima,
Temperature Stability and pH Stability of Aip ...................................... 130 9.3.2.2 Scanning Electron Microscopy (SEM) and Energy Dispersive
X-Ray Spectrometry (EDS) ................................................................... 130 9.3.3 Removal of Cadmium (II) Using AIP .................................................... 132 9.3.3.1 Kinetics Study .......................................................................... 132 9.3.3.2 Equilibrium Study .................................................................... 137
9.3.3.3 Determination of Optimum Condition for Removal of Cadmium (II) By AIP using Response Surface Methodology............... 138
9.3.4 Recovery of Cadmium (II) .................................................................... 141 9.4 Conclusion ....................................................................................................... 141 Keywords ................................................................................................................. 141 References ................................................................................................................ 141
9.1 INTRODUCTION
Cadmium is introduced to the environment through the discharge of a number of industries viz. electroplating, pigments, steel, batteries, solar panel and plastic and so on. Industrial effluents containing cadmium (II) need proper treatment due to the toxic effect of cadmium on living system. Bulk methods like filtration or precipitation are often practiced but they are unable to bring down the concentration to the µg/l level. The goal of this research is to remove cadmium (II) from simulated aqueous solution by immobilized papain (E.C. 3.4.22.2), a low cost proteolytic enzyme having four sulfhydryl groups which strongly bind with heavy metals. Papain has been immobilized in calcium alginate by entrapment method under the following conditions-–initial concentration of sodium alginate: 20 g/l, initial concentration of calcium chloride: 20 g/l, initial concentration of papain: 25.96 g/l, pH: 7.0, temperature 35°C and hardening time: 30 min. Papain immobilized in calcium alginate under this condition has been designated as Alginate Immobilized Papain (AIP). Removal of cadmium (II) from simulated solution, kinetics and equilibrium studies has been performed using AIP. The optimum condition for removal of cadmium (II) is determined by Response Surface Methodology (RSM) using Design Expert Software 8.0.5. To get the optimized removal condition three input functions viz. initial concentrations of cadmium (II) weight of AIP and pH have been varied according to the experimental design as approved by software. Five gram of AIP, pH 7 and initial concentration of cadmium (II) 26.41 mg/l at 35°C have been found to be the optimum condition for removal resulting in about 93% removal of cadmium (II) from simulated solution. The adsorption kinetics of this metal has been governed by chemisorptions process as the data fit most satisfactorily to Pseudo Second Order Model (PSOM). Results reveal that the equilibrium data fit most satisfactorily with Langmuir adsorption isotherm model. Cadmium (II) is recovered from treated AIP by altering the pH of the cadmium-loaded beads. The result suggests that use of AIP could be an alternative method for removal and recovery of cadmium (II) from industrial waste.
