Equilibrium, kinetics and artificial intelligence characteristic analysis for Zn (II) ion adsorption on rice husks digested with nitric acid

摘要

The use of low-cost adsorbents produced from rice husks that can selectively remove zinc (II) ion from wastewater effluent has been investigated. The disorder and fatal diseases can be triggered in living organisms by accumulating the heavy metals in the wastewater. Adsorption is an operative cleansing and separation method used in the industry to remove contaminants from effluents. In order to convert the rice husk to the adsorbent, digestion and carbonization processes were performed. Rice husks digested nitric acid at 1.0 M to reduce the organic constituents and further carbonized at 400, 600 and 800 degrees C to eliminate the non-carbon element in rice husks. The physiochemical characteristics of the digested and carbonized rice husks were analyzed using scanning electron microscope (SEM), X-ray diffraction (XRD) and atomic adsorption spectrophotometer (AAS). The SEM morphological characteristics showed the high pyrolysis effect on the organic matter left the samples with more pores and cavities, which enhanced the surface area and uptake, especially for 800 degrees C carbonized samples. The samples' physical characteristics using XRD showed that the treatment with HNO3 illustrated a pattern close to the activated carbon with slightly lower intensities. The applied feed-forward back-propagation neural network algorithm showed high validity (R-2 approximate to 0.9686) for the tested experimental data sets and hence can be applied for forthcoming studies with nearby conditions. The outcomes showed that the increment of the carbonization temperature is correlated with the contact time and can increase the metal uptake percentage and adsorption capacity. The adsorption followed the Langmuir isotherm, which indicates monolayer coverage. The data showed that adsorption kinetics follow the pseudo-second-order rate expression.