Implementation and physico-chemical characterization of new alkali-modified bio-sorbents for cadmium removal from industrial discharges: Adsorption isotherms and kinetic approaches

This study consists of using for the first-time new alkali-modified natural adsorbents as underused lignocellulosic remains in a physicochemical adsorption process, to treat polluted discharges of industrial origin. Four different lignocellulosic materials were mercerized using sodium hydroxide (NaOH) and tested to investigate their ability to adsorb cadmium II (Cd2+) as a toxic heavy metal ion. The physicochemical features and the performance of the bio-sorbents were evaluated by FTIR, BET, SEM, TGA, XRD and zeta potential analysis. The influence of different experimental parameters (solution pH, temperature, contact time, and Cd2+ concentration) was studied. Results showed that the treated bio-sorbents exhibited remarkable elimination from the first 25 min. Among the used lignocellulosic materials red algae (RA) exhibited the highest adsorption percentages (99.54%) at neutral pH (7) and room temperature (25 degrees C). Interestingly, the kinetic adsorption model (pseudo-secondary order) adequately simulates the Cd2+ adsorption behavior. Also, Langmuir model exhibited a correlation coefficient (R2) close to 1. These results demonstrated high adsorption capacities of all the lignocellulosic materials used. Accordingly, their physico-chemical characterization and application can open new perspectives for the development of high valueadded materials from under-exploited lignocellulosic products.