A novel Ni–Ca–hydroxyapatite solid acid catalyst was prepared through wet impregnation of Ni(NO3)2·6H2O on pretreated waste fish scale (PWFS) support, and the catalyst was characterized by TGA, XRD, FESEM, BET, BJH, and FTIR methods. The efficacy of the developed catalyst possessing a specific surface area of 90 m2/g, 0.1823 cm3/g pore volume, 54.83 nm modal pore diameter, and 7.52 mmol NaOH/g catalyst acidity was evaluated through esterification of free fatty acids (FFAs) of pretreated waste frying soybean oil (PWFSO) in a semibatch reactor . Optimal parametric values for esterification computed using response surface methodology (RSM) corresponding to maximum (i.e., 59.90%) conversion of FFAs to yield FAME (biodiesel) were 0.80 mL/min methanol flow rate, 30 wt % Ni(NO3)2·6H2O precursor dosage, and 300 °C calcination temperature. Subsequent batch transesterification of the unreacted triglycerides present in upstream product catalyzed by calcined fish scale (base catalyst) resulted in an ultimate 98.40% yield of biodiesel.

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A (t, n) threshold secret image sharing scheme generates n share images from a secret image in such a way that any t or more share images can be used to reconstruct the secret image. In this paper we have proposed a (t, n) secret image sharing scheme where the secret image is first encoded by block based lossy compression technique and define t sub-images. The image compression technique gives a good quality image. To enhance the security level, the sub-images are scrambled by Arnold transform and then shares are generated. Finally, image hiding (i.e., steganography) concept is adopted to hide the shares within cover images. The proposed method gives good quality of the stego images.

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