Study of the adsorption, desorption and phitotoxicity of Pb, Cd and Zn adsorbed in biochar of rice husk

Abstract

Potentially toxic metals (PTM) include both elements that are considered essential and non-essential. They occur naturally in the environment, most of the time in low concentrations, depending on the geological material. It is noteworthy that anthropic activities interfere with the biogeochemical cycle of PTMs, which can cause them to reach levels that are toxic to the ecosystem, mainly due to the increased concentration of non-essential elements. In toxic levels, PTMs can cause inhibition of plant growth, modification of soil biota, causing mortality, etc. Due to the capacity of bioaccumulation these metals can even at low concentrations, reach levels harmful to the fauna and flora. Also, assimilated by producers, the PTMs can biomagnify and impact the entire food chain. There are several areas in Brazil and in the world contaminated by lead (Pb), zinc (Zn) and cadmium (Cd). Due to all this complexity, it is necessary to remediate areas degraded by PTMs. In this context, it is extremely important to evaluate reactive materials capable of adsorbing these metals. The use of biochar, as an adsorbent material, has been gaining space in the remediation of contaminated areas. Waste from various sources is being pyrolyzed to generate biochars. This research, intend to study the biochar from rice husk pyrolysis in the adsorption of Cd, Pb Zn. In addition to adsorption, it is necessary to evaluate whether after the metals are adsorbed, they can be desorbed, under different environmental conditions. The phytotoxicity in the solution resulting from the adsorption test helps to better understand the effectiveness of such adsorption by the biochar.(AU)