Person: Ruhl, Aki Sebastian
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Aki Sebastian
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Veröffentlichung Comparing fine particulate iron hydroxide adsorbents for the removal of phosphate in a hybrid adsorption/ultrafiltration system(2019) Hilbrandt, Inga; Shemer, Hilla; Ruhl, Aki SebastianThe use of micro-sized iron hydroxide adsorbents in mixed reactors is a promising technique for the removal of inorganic contaminants from wastewater within minutes of contact time. This study focusses on phosphate adsorption onto fine fraction granular ferric hydroxide (nGFH) and iron oxy(hydr)oxide agglomerates (IOAs) in a reactor with submerged ultrafiltration (UF) membrane. The performance of the hybrid adsorption/UF membrane system was evaluated for various adsorbents and phosphate concentrations, residence times and concentrations of co-existing ions. The membrane was not fouled at the experimental conditions used (up to 6.3 g/L adsorbent). Phosphate loadings of 20 and 60 mg P/g Fe (36.1 and 108.3 mol P/mol Fe) were reached for nGFH and IOAs, respectively (C0(P) = 4.5 mg/L, deionized water at pH 8, C(Fe) = 0.6 g/L). A shortened residence time of 15 min in the reactor led to a decrease in final loading of 6 mg/g compared to 30 min residence time (54 mg/g compared to 60 mg/g). An extension to 60 min did not result in higher loadings. An increase in adsorbent (IOA) concentration from 0.1 to 0.3 mg/L resulted in an increase of phosphate removal (27 to 35%). Simultaneously, loadings decreased from 50 to 35 mg/g. The application of the developed process for the treatment of artificial secondary effluent resulted in an increase of 87 and 60% in treated volumes until breakthrough (50%) for nGFH and IOAs, respectively, compared to deionized water. Thus, the combined process of adsorption and particle separation using a submerged membrane can be well adjusted according to water composition, initial pollutant concentrations and desired removals. © 2019 Elsevier B.V. All rights reserved.Veröffentlichung Quantification and isotherm modelling of competitive phosphate and silicate adsorption onto micro-sized granular ferric hydroxide(2019) Hilbrandt, Inga; Lehmann, Vito; Zietzschmann, Frederik; Ruhl, Aki SebastianAdsorption onto ferric hydroxide is a known method to reach very low residual phosphate concentrations. Silicate is omnipresent in surface and industrial waters and reduces the adsorption capacity of ferric hydroxides. The present article focusses on the influences of silicate concentration and contact time on the adsorption of phosphate to a micro-sized iron hydroxide adsorbent (nGFH) and fits adsorption data to multi-component adsorption isotherms. In Berlin drinking water (DOC of approx. 4 mg L-1) at pH 7.0, loadings of 24 mg g-1 P (with 3 mg L-1 initial PO43--P) and 17 mg L-1 Si (with 9 mg L-1 initial Si) were reached. In deionized water, phosphate shows a high percentage of reversible bonds to nGFH while silicate adsorption is not reversible probably due to polymerization. Depending on the initial silicate concentration, phosphate loadings are reduced by 27, 33 and 47% (for equilibrium concentrations of 1.5 mg L-1) for 9, 14 and 22 mg L-1 Si respectively. Out of eight tested multi-component adsorption models, the Extended Freundlich Model Isotherm (EFMI) describes the simultaneous adsorption of phosphate and silicate best. Thus, providing the means to predict and control phosphate removal. Longer contact times of the adsorbent with silicate prior to addition of phosphate reduce phosphate adsorption significantly. Compared to 7 days of contact with silicate (c0 = 10 mg L-1) prior to phosphate (c0 = 3 mg L-1) addition, 28 and 56 days reduce the nGFH capacity for phosphate by 21 and 43%, respectively. Quelle: https://pubs.rsc.orgVeröffentlichung Conditioning fixed-bed filters with fine fractions of granulated iron hydroxide (MyGFH)(2018) Hilbrandt, Inga; Jekel, Martin; Ruhl, Aki SebastianThe fine fraction of granular ferric hydroxide (MyGFH, < 0.3 mm) is a promising adsorbent for the removal of heavy metals and phosphate, but properties of MyGFH were hitherto not known. The present study aimed at characterizing MyGFH regarding its physical and chemical properties and at evaluating methods for the conditioning of fixed-bed filters in order to develop a process that combines filtration and adsorption. Conditioning was done at different pH levels and for different particle sizes. Anthracite, coke, pumice and sand were studied as potential carrier materials. A method for the evaluation of the homogeneity of the iron hydroxide particle distribution on pumice filter grains using picture analysis was developed. Pre-washed pumice (pH 8.5) proved to lead to high embedment and a homogeneous distribution of MyGFH. Filter runs with phosphate (2 mg/L P) showed similar breakthrough curves for the embedded fine fraction adsorbent and for conventional GFH. © 2018 by the authors.Veröffentlichung Competition in chromate adsorption onto micro-sized granular ferric hydroxide(2019) Hilbrandt, Inga; Ruhl, Aki Sebastian; Zietzschmann, FrederikHexavalent chromium is highly toxic and elaborate technology is necessary for ensured removal during drinking water production. The present study aimed at estimating the potential of a micro-sized iron hydroxide (nGFH] adsorbent for chromate removal in competition to ions presents in drinking water. Freundlich and Langmuir models were applied to describe the adsorption behaviour. The results show a high dependency on the pH value with increasing adsorption for decreasing pH values. The adsorption capacity in deionized water (DI) at pH 7 was 5.8mg/g Cr(VI) while it decreased to 1.9mg/g Cr(VI) in Berlin drinking water (DW) at initial concentrations of 1.2mg/L. Desorption experiments showed reversible adsorption indicating ion exchange and outer sphere complexes as main removal mechanisms. Competing ions present in DW were tested for interfering effects on chromate adsorption. Bicarbonate was identified as main inhibitor of chromate adsorption. Sulfate, silicate and phosphate also decreased chromate loadings, while calcium enhanced chromate adsorption. Adsorption kinetics were highly dependent on particle size and adsorbent dose. Adsorption equilibrium was reached after 60ââą ¯min for particles smaller than 63nm, while 240 min were required for particles from 125nm to 300nm. Adsorption kinetics in single solute systems could be modelled using the homogeneous surface diffusion model (HSDM) with a surface diffusion coefficient of 4x10-14m2/s. Competitive adsorption could be modelled using simple equations dependent on time, adsorption capacity and concentrations only. © 2018 Elsevier Ltd. All rights reserved.