Ammonia removal from tannery wastewater using calcined eggshell

Abstract

Ammonia pollution has become a severe problem for aquatic livestock. A high concentration of ammonia content causes life risks for fishes and animals in the water bodies. Ammonia is introduced in wet lands from different anthropogenic activities like leather manufacturing, paper pulp etc. In this study calcined eggshells were used to remove ammonia from tannery wastewater. Raw eggshells contain 97.50 % CaCO3 which is converted into 97.40 % CaO via calcination at 900 °C for 3 hours of heat. Physical, chemical, and morphological properties of raw, calcined, and ammonia loaded treated eggshells are studied. Off-white, odorless raw eggshell regained bright white color and converted to soft powder in calcined phase. Thermal characteristics were studied by Differential Scanning Calorimeter (DSC) and Thermo Gravimetric Analysis (TGA). The STA analysis indicated the phase transformation from raw eggshell (RES) to calcined eggshell (CES) with gradual increases in temperature and beyond 680 °C to 880 °C (̴ 900 °C) temperature CaCO3 turned into CaO. Furrier Transform Infrared Spectroscopy (FTIR) reflected group generated in calcined eggshell (CES) which is occupied after treatment of tannery wastewater. Ammonia loaded eggshell powder showed a sharp, medium N-H bond at wavenumber 2934.79 cm-1. Morphological structure of RES, CES, and loaded eggshell are analyzed by scanning electron microscope (SEM) and X-Ray Fluorescence Spectroscopy (XRF) studied to detect chemical composition among the different three phases of eggshells. 97.40 % CaO reduced to 87.84 % after reduction of different pollution loads from tannery wastewater and XRF result said that 3.54 % SO3 increased in loaded eggshell. Physicochemical parameters of tannery wastewater were studied before and after treatment by CES and compared with the allowable limit. Different three wastewater samples were tested with an adsorbent dose of 4 gm/L. BOD5, COD, TSS were reduced whereas EC, TDS, pH, and turbidity were increased due to the use of calcined eggshells. Initial ammonia content was 242.5 mg/L which was decreased to 57 mg/L at pH 12.47. 99.9 % chromium reduction has been achieved by CES through the adsorption process. Adsorbent dose 4 gm/L and maximum removal efficiency have achieved 76.29% within only 10 minutes of reaction time. Reaction kinetics were calculated using a linear line graph reaction coefficient. Pseudo first order and pseudo-second-order reaction kinetics give heterogeneity and unoccupied sites of CES. Langmuir isotherm declared physical adsorption of ammonia occurred with CES and RL of this isotherm model is greater than 0 and less than 1. Therefore adsorption is favorable on the other hand, n values of Freundlich isotherm model have calculated less than 1 thus poor multilayer adsorption has occurred. The favorable pH for the ammonia removal was 12.47, which was achieved using the aforementioned amount of CES. Therefore, pH is one of the parameters which influence ammonia removal. The performance and potentiality of CES would be an invention for the treatment of ammonia removal and reduced pollution load from the tannery wastewater.