ABSTRACT
The pristine CMK-3 carbon was ozonized and then chemically modified by the Zr and Fe compounds. The synthesized carbonaceous materials were characterized with physicochemical methods. The obtained carbons had a high specific surface area (ca. 800 m2 g-1) and an acidic surface. The Cr(VI) adsorption properties of the oxidized and Zr/Fe-modified carbon were studied. The highest static adsorption capacity towards Cr(VI) ions was evaluated for Zr/Fe-modified carbon (50.1 mg g-1) at pHeq = 5.8 after 240 min. The Elovich and Freundlich theoretical models were well fitted to the Cr(VI) adsorption kinetic and isotherm data on the Zr/Fe-modified CMK-3-type carbon. The leading Cr(VI) adsorption mechanism acting on the Zr/Fe-modified carbon was probably based on the redox reactions between Cr(VI) and the carbonaceous surface. Electrostatic attraction and surface complexation processes could also occur during Cr(VI) adsorption in the studied system. The effect of the competitive anions on the concentration level, such as in the galvanic wastewater for Cr(VI) adsorption onto chemically modified carbon, was negligible. The HCl and HNO3 media were insufficient for the Zr/Fe-modified carbon regeneration after Cr(VI) adsorption. The Zr/Fe-modified carbon was successfully applied for the efficient (>90%) Cr(VI) removal from the model galvanic wastewater.
ABSTRACT
Newly synthesized cerium oxide was successfully obtained by the hard templating route. The optimal As(III) and As(V) adsorption onto the studied adsorbent was reached for the initial pH of 4.0 and a contact time of 10 h. The highest static adsorption capacities for As(III) and As(V) were 92 mg g-1 and 66 mg g-1, respectively. The pseudo-second-order model was well fitted to the As(III) and As(V) experimental kinetics data. The Langmuir model described the As(III) and As(V) adsorption isotherms on synthesized material. The adsorption mechanism of the studied ions onto the synthesized cerium oxide was complex and should be further investigated. The optimal solid-liquid ratio during the proposed aqueous extraction of inorganic As from the Fucus vesiculosus algae was 1:50. The optimal dosage of the synthesized cerium oxide (0.06 g L-1) was successfully applied for the first time for inorganic As removal from the aqueous algal extract.
ABSTRACT
Novel CO2- and H3PO4-modified biochars were successfully synthesized from raw honeycomb biomass. They were characterized via several instrumental techniques. The optimal Pt(II) and Pt(IV) adsorption onto the studied biochars was reached for the initial pH of 1.5 and a contact time of 5 min (Pt(II)) and 24-48 h (Pt(IV)). The highest static adsorption capacities for Pt(II) and Pt(IV) were obtained for the H3PO4-modified biochar: 47 mg g-1 and 35 mg g-1, respectively. The Freundlich model described the Pt(II) adsorption isotherms onto both materials and the Pt(IV) adsorption isotherm onto the CO2-activated material, and the Langmuir model was the best fitted to the Pt(IV) adsorption isotherm onto the H3PO4-activated biochar. The best medium for the quantitative desorption of the Pt form from the H3PO4-modified biochar was 1 mol L-1 thiourea in 1 mol L-1 HCl. The adsorption mechanism of both the studied ions onto the synthesized H3PO4-modified biochar was complex and should be further investigated. The H3PO4-modified biochar was successfully applied for the first time for Pt(IV) removal from a spent automotive catalyst leaching solution.
