Synergistic effect of silver nanoparticle-embedded calcite-rich biochar derived from Tamarindus indica bark on 4-nitrophenol reduction.

Calcite-biochar composites are attractive materials with outstanding adsorption capabilities for removing various recalcitrant contaminants in wastewater treatment, however, the complexity of their synthesis limits their practical applications. In this work, we have prepared calcite-rich biochar (Ca-BC) from a single precursor (Tamarindus indica bark), which simplifies the synthetic route for preparing calcite-biochar composite. The as-synthesized composite is utilized to make a heterogeneous catalytic system containing the supported silver nanoparticles (Ag@Ca-BC) formed by the reduction of Ag ions on the surface of the composite. The formation of Ag@Ca-BC is confirmed by various characterization techniques such as PXRD, FT-IR, UV-Vis, cyclic voltammetry, impedance measurement, SEM, and TEM analyses. Especially, the TEM analysis confirms the presence of Ag nanoparticles with size ranging between 20 and 50 nm on the surface of Ca-BC composite. The nano-catalyst Ag@Ca-BC efficiently promotes the conversion of 4-nitrophenol to 4-aminophenol using NaBH as the reductant in water within 24 minutes at room temperature, suggesting that Ag@Ca-BC can be an efficient catalyst to remove nitroaromatics from the industrial effluents. The straightforward synthesis of Ca-BC from a single precursor along with its utility as a catalytic support presents a compelling proposition for application in the field of materials synthesis, catalysis, and green chemistry.