Biosorption of Heavy Metal From Cadmium Rich Aqueous Solutions by Tea Waste as a Low Cost Bio-Adsorbent

Abstract

Background: Heavy metals pollution is a serious threat to environment and human health. Therefore, it is vital to find an effective method to remove heavy metals from natural resources. Objectives: The current study aimed to investigate the adsorption capacity of cadmium from synthetic solution by tea waste as a biomass. Methods: The experiments were conducted in batch system and the effect of pH, adsorbent quantity, contact time and the initial concentration of cadmium were examined. The most common isotherms and kinetics of adsorption were applied to analyze cadmium adsorption and the reaction rate. Moreover, morphological characteristics before and after the adsorption process and also molecular structures of tea waste were determined by scanning electron microscope (SEM) and Fourier transform infrared spectrometry (FTIR); also, the surface area size of tea waste was measured using Brunauer-Emmett-Teller (BET). Results: According to the results, the maximum efficiency of cadmium adsorption was 99.50% obtained in pH of 5 and contact time of 90 minutes and 10 g/L of adsorbent. With the increase of initial concentration of cadmium, the amount of the adsorbed metal increased, but the removal percentage decreased. Data for this study indicated a good correspondence with both isotherms of Longmire and Freundlich. The analysis of kinetic indicated that cadmium adsorption was consistent with the second-degree kinetic adsorption model. Conclusions: According to the high efficiency of cadmium elimination by tea waste, this approach is applicable as an efficient and affordable trend to remove cadmium from aqueous solution without any chemical or physical pre-treatment.