The present study investigates uptake of Cr(VI) from synthetic metal solution by superheated steam-activated biochar (SABC) made from roots of Colocasia esculenta and synthetic zeolite (ZRHA) prepared from rice husk ash under the influence of pH (1–7), adsorbent dose (1–100 mg/L), initial Cr(VI) concentration (5–190 mg/L), temperature (15–55 °C), agitation speed (100–170 rpm) for a contact time of 30–1440 min. ZRHA and SABC were able to remove metal ions from a stock solution of 90 and 110 mg/L of Cr(VI) with a removal of 85.89% and 94.8%, respectively. Metal ion adsorption onto zeolite ZRHA followed monolayer adsorption, whereas biochar SABC employed multilayer adsorption. Kinetic studies suggested that adsorption of Cr(VI) ions could follow both physisorption and chemisorption depending on the adsorbent used. The two-compartment dynamic model study revealed Cr(VI) adhesion followed a slow phase of adsorption which suggested intraparticle diffusion to be a prominent rate-limiting factor for both cases. The thermodynamic study claimed that Cr(VI) adsorption was a temperature dependent phenomenon. Instrumental studies by TEM, SEM, EDX and FT-IR also advocated their part on Cr(VI) removal. Also, crystallinity of both the adsorbents was determined from their XRD analysis. Thus, the current study promotes both ZRHA and SABC to be a promising adsorbent for Cr(VI) removal from contaminated aqueous solution.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
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