Novel Fe-Mn binary oxide-biochar as an adsorbent for removing Cd(II) from aqueous solutions

In this study, a pristine biochar (BC) and Fe-Mn binary oxide-biochar (FMBC) were prepared using Pennisetum sp. straw as the feedstock for Cd(II) removal from aqueous solutions. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and specific surface area (SSA) analyses revealed the physico-chemical characteristics of the pristine and designer adsorbents, suggesting that an ultrasonic treatment during synthesis enhanced the SSA and pore volume of the BC, and assisted successful loading of Fe-Mn binary oxide particles on the BC surface. The Cd(II) adsorption data of the adsorbents were fitted to the Langmuir isothermal and pseudo-second-order kinetic models. At a system temperature of 25 °C and pH 5, the maximum Cd(II) adsorption capacities of BC (30.58 mg/g) and FMBC (95.23 mg/g) were obtained. Multiple Cd(II) adsorption mechanisms by FMBC were identified, including precipitation with minerals, complexation with surface functional groups, Cd(II)-π interactions, and cation exchange. As the most dominant adsorption mechanism, Cd-O bonds were formed on the FMBC surfaces precipitating Cd(OH)2 (63.9 wt%) and CdO (36.1 wt%). The FMBC thus could be potentially used as an effective adsorbent for Cd(II) removal from aqueous solutions

Removal of Chelated Copper by TiO 2 Photocatalysis: Synergetic Mechanism Between Cu (II) and Organic Ligands

ABSTRACT: UV/TiO 2 photocatalysis of chelated copper in aqueous solutions has been performed starting from Cu(II)-tartaric acid, Cu(II)-citric acid, Cu(II)-EDTA and Cu(II)-DTPA, in the presence of oxygen and at acidic pH. The photocatalytic reaction obeys first-order kinetic equation. The influence of Cu(II) on photocatalytic oxidation of organic ligands and how the various organics will affect the treatment of Cu(II) were described. A significant synergistic effect was observed between the reduction of Cu(II) and oxidation of organic ligands. The results prove that TiO 2 photocatalysis is an effective approach for removing chelated copper from wastewater

Influence of Aged Biochar Modified by Cd2+ on Soil Properties and Microbial Community

Biochar is a promising addition for cadmium-contaminated soil in-situ remediation, but its surface properties change after aging, cadmium adsorption is not well-documented, and subsequent environmental effects are still unknown. In this study, wood-derived (Eucalyptus saligna Sm.) biochar was pre-treated to simulate aging and the cadmium sorption process. We then analyzed the resulting physicochemical characteristics. We conducted comparative incubation studies on three age stages of biochar under cadmium adsorption or no cadmium adsorption and then measured soil properties and microbial communities after incubation. Biochar addition raised soil organic carbon (SOC), and aging significantly increased C/N ratios. Aged biochar promoted higher microbial abundance. Aged biochar treatments possessed different microflora with more gram-positive bacteria, significantly altering gram-positive/gram-negative bacteria ratios. Aging significantly increased the oxygen-containing functional groups (OCFGs) and surface area (SA) of biochar. Thus, aged biochar adsorbed more cadmium. Cadmium-binding biochar increased the proportion of gram-negative bacteria and decreased the proportions of gram-positive bacteria and fungi. Similar patterns in phospholipid fatty acids (PLFAs) across adsorption treatments indicated that changes in microbial communities due to the effects of cadmium were confined. The results reveal that biochar aging altered microbial community structure and function more than cadmium binding