Investigation of competitive adsorption and desorption of heavy metals from aqueous solution using raw rock: Characterization kinetic, isotherm, and thermodynamic

Heavy metals are the most dangerous inorganic pollutants Due to their bioaccumulation and their nonbiodegradability, for this, several studies have focused on the recovery of these metals from water using different techniques. In this context, our study consists of evaluating an efficient and eco-friendly pathway of competitive recovery of heavy metals (Cd, Cr and As) from aqueous solutions by adsorption using raw rock. This adsorbent was characterized before and after the adsorption process by several techniques. The multi-metals adsorption process in the batch mode was undertaken to evaluate the effect of adsorbent mass, contact time, pH, Temperature, and initial heavy metals concentration. The kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. According to the modeling of the experimental results, the adsorption kinetics of heavy metals were adapted to the pseudo-second-order model. The adsorption isotherms were evaluated by the Langmuir and Freundlich isotherm models. The experimental isotherm data of heavy metals were better fitted with the Langmuir model rather than Freundlich isotherm models. The maximum experimental adsorption capacities (Qmax) predicted by the Langmuir model are 15.23 mg/g for Cd (II), 17.54 mg/g for Cr (VI) and 16.36 mg/g for As (III). The values of thermodynamic parameters revealed that the heavy metals adsorption was exothermic, favorable, and spontaneous in nature. The desorption process of heavy metals showed that this raw rock had excellent recycling capacity. Based on the results, these untreated clays can be used as inexpensive and environmentally friendly adsorbents to treat water contaminated by heavy metals.

EFFICIENCY OF NATURAL SORBENTS IN ADSORPTION OF HEAVY METAL IONS

The article provides research on testing natural sorbents based on peat, diatomite and vermiculite during the adsorption of heavy metal ions (Pb, As, Cr, Cr6+, Cr3+, Cu). The following series of sorbents has been formed according to the efficiency of adsorption of heavy metal ions from aqueous solutions of salts: peat - granular diatomite> coarse vermicu-lite> medium fraction vermiculite> peat - non-granular diatomite> diatomite. Key words: natural sorbents, ameliorants, disturbed lands, heavy metals, adsorption, recultivation, bioremediation.

THE INITIAL ION EFFECT OF HEAVY METALS ADSORPTION BY USING HYDROTHERMAL CARBONIZATION BANANA PEELS

Accumulation of heavy metals in water is of particularly important because it can impact upon human health through possible contamination of food. The use of banana peel was investigated. Hydrothermal carbonization (HTC) was chosen as alternative process. The objective of this project is to synthesize banana peel hydrochars adsorbent via HTC process and to evaluate the heavy metals adsorption performance of banana peel hydrochars adsorbent. Conventional methods in removal of heavy metals require high operational cost, need highly skilled labour, and generate sludge at the end of the operation. Compared to other techniques, banana peel absorbent is a cost- effective adsorbent, easy to operate, environmentally safe and no health risk for the operator. Besides, large quantity of banana peel waste contributes to its significant disposal problem. Thus, this study is expected to solve problems of banana peel, by preparing banana peel adsorbent through hydrothermal carbonization. There are three phases in this project, phase 1 which is synthesis of banana peel based on hydrochars, banana peel was chopped the peels into small pieces. It was then soaked in KOH solution for 2hours and transferred into PTFE and heat for 2hours at 230°C. For phase 2, physico-chemical characterization of banana peels hydrochars by using FTIR. The result obtained shown that all of the content in banana peels will activate the surface of banana peel to enhance the adsorption of the heavy metals. For the final phase, by using AAS, the initial and final concentration of the metals was tested to determine the removal of heavy metals by the prepared hydrochars. The results showed that the removal capacity of the hydrochars increased when the initial concentration of the metals increased. From the research, it can be concluded that, as the initial concentration of the metals higher, the ability of the hydrochars to remove the metals also higher and stronger.