Copper adsorption on composites of goethite, cells of Pseudomonas putida and humic acid

Abstract

In the soil environment, iron oxides co‐occur commonly with different types of organic constituents to produce iron oxide–organic composites that play an important role in the biogeochemical cycling of trace metals. We investigated copper (Cu) adsorption on synthetic goethite, Pseudomonas putida (CCTCC M209319) bacterial cells, humic acid (HA) and their binary and ternary composites with batch adsorption experiments coupled with isothermal titration calorimetry (ITC). Morphological characterizations show that the three components can form closely combined and heterogeneous aggregates with one another. The kinetics of sorption of Cu to these composite materials conforms to the pseudo‐second‐order model, whereas the Cu sorptivities deviate from linear additivity. Specifically, Cu sorptivities on the binary goethite–P. putida and P. putida–HA and ternary goethite–P. putida–HA composites are less than expected assuming additivity, whereas the opposite is seen for the binary goethite–HA composite. There is considerable masking of adsorption sites in the ternary goethite–P. putida–HA system, but the binding sites on bacteria are not completely covered, as shown by the adsorption enthalpy and entropy (19.60 kJ mol−1 and 120.9 J mol−1 K−1, respectively) for the ternary composite. We conclude that the binding affinity of Cu for the binary goethite–humic acid composite is larger than that for the bacterial composites with goethite or humic acid, or both. This research indicates that bacteria, iron oxide and humic substances exhibit different behaviour in the sequestration of heavy metals when they form various binary and ternary complexes in natural environments. Highlights How does mineral–organic interaction affect the binding behaviour of trace elements? First investigation of Cu sorption to goethite–bacteria–humic acid composites. Goethite–HA shows enhanced Cu adsorption, whereas the opposite is true for bacterial complexes. Various bacteria–iron oxide–humic substance composites behave differently in metal sequestration.

Natural organic matter decreases uptake of W(VI), and reduces W(VI) to W(V), during adsorption to ferrihydrite

“…S1) provides a good fit to the data (≥0.92), and is used to obtain the kinetic adsorption parameters. This model has been widely used in describing the kinetics of metal adsorption to a variety of sorbents (Zhu et al, 2011;Du et al, 2017;Yan et al, 2017). The Pseudo-second order model can be expressed as: 1∕(qe-qt) = 1∕qe + kt, where qe is the equilibrium adsorption amount and k represents the rate constant.…”

“…These findings also corroborate that W(VI) adsorption is suppressed in the presence of HA. The entropy changes (ΔS) can further provide information on the coordination environments of the adsorbed W oxyanions, i.e., inner-sphere complex formation commonly generates a positive ΔS while outer-sphere complex formation produces a negative ΔS because the former displaces solvating water molecules from the adsorption coordination sites, whereas the latter does not (Nancollas, 1970;Gorman-Lewis et al, 2006;Du et al, 2017). Our ΔS data (12.96-15.03 J/mol/K) therefore provide clear evidences for the formation of inner-sphere type of W species on Fh and Fh-HA surfaces.…”

Sorption of Pb(II) by Nanosized Ferrihydrite Organo-Mineral Composites Formed by Adsorption versus Coprecipitation

“…2 Iron− OM interactions play a key role in stabilization of organic carbon against microbial degradation 3,4 and they are also capable of controlling the speciation and mobility of nutrient elements and heavy metals in geological and aqueous systems, because iron oxide and organic matter are both effective scavengers of dissolved metals. 5,6 Nanostructured two-line ferrihydrite (Fh) is an attractive sorbent for cations such as Pb 2+ , Cd 2+ , Cu 2+, and Zn 2+ with the largest Langmuir monolayer adsorption capacity of 366, 250, 62.5, and 500 mg/g, respectively. 7 These metals are sorbed as inner-sphere complexes with the Fe(O,OH) 6 polyhedra of the ferrihydrite.…”

Perspectives of Microbial Inoculation for Sustainable Development and Environmental Management

“…In soil environments, iron oxides make complexes with organic composites and help in the transformation trace metals. Du et al (2017b) studied the copper adsorption on composites of synthetic goethite, cells of Pseudomonas putida , humic acid (HA), and their binary and ternary composites with batch adsorption experiments coupled with ITC. They reported that bacterial composites with goethite or humic acid separately and in combination help in adsorption and cycling of Cu but their affinity was less than binary composite of goethite and humic acid.…”