Novel ferrihydrite sand coating process as a first step for designed technosols

• Published in: Journal of soils and sediments Vol. 18; no. 11; pp. 3349 - 3359
• Main Authors: Flores-Ramírez, Eleonora, Dominik, Peter, Kaupenjohann, Martin
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2018; Springer Nature B.V
• Subjects: Adsorption; Adsorptivity; Aggregates; Amorphous materials; Capacity; Coating effects; Coatings; Detaching; Earth and Environmental Science; Electron microscopy; Environment; Environmental Physics; Ferric chloride; Iron; Iron chlorides; Knowledge bases (artificial intelligence); Minerals; Neutralization; Phosphates; Sand; Scanning electron microscopy; Shaking; Soil; Soil pollution; Soil remediation; Soil Science & Conservation; Soil stabilization; Sorption; Stability; Substrates; SUITMA 8: Soils and Sediments in Urban and Mining Areas; Surface charge; Surface chemistry; Surface stability; Surface structure; Zeta potential; Iron-coated sand; 2-line-ferrihydrite; Iron (hydr)oxides; Stability; Constructed soil; Technosol
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-016-1450-1

Purpose The production of technosols to remediate polluted or sealed urban soils to sustain new green areas is mainly empirical. For this, our research aims to contribute with the scientific knowledge base for purpose designing of technosols. Since iron minerals play an important role for many different functions of soils, we simplified a technique to incorporate and stabilize iron minerals in a substrate: a sand coated with an amorphous iron (hydr)oxide, a 2-line ferrihydrite (2L-FH). Materials and methods The 2L-FH was precipitated by neutralization of a concentrated FeCl 3 solution. The suspension was homogeneously mixed with the sand and the mixture was dried at 35 °C. The mechanical stability of the 21 2L-FH-coated sand was determined by shaking the aggregates in water for 0, 1, 10, 100, and 1 000 min. The degree of coating detachment and the properties of the coating after shaking were characterized through (a) Fe content, (b) zeta-potential and particle size of the detached particles, (c) the specific surface area (SSA) of the coated sand, and (d) its surface structure using scanning electron microscopy (SEM). A phosphate adsorption isotherm was performed to measure the P-sorption capacity of the shaken samples and to test the 2L-FH-quartz attachment stability against the surface charge reduction of the 2L-FH associated with P adsorption. Results and discussion A reduced Fe loss (30 %) and smaller sizes of the coating detached particles in the sample shaken for 1 000 min indicate that a fractioning and reattachment of these aggregates occurred during the agitation process, resulting in a smoother surface (SEM), and a larger SSA and P-sorption capacity. The coated shaken samples showed P-adsorption capacities (5.3–6.34 μ mol P g −1 ) comparable to high loadings of phosphate in soils, and low detachment of Fe (7–14 %) in spite of negativity surface charge increase. Conclusions The practical novel coating process along with the 1 000-min shaking produced a mechanical resistant and P-adsorptive effective coated sand that could sustain the needs of plants in further experiments.