Comparison of APTES-Functionalized Silica Fiber and Clinoptilolite for Reducing Iron Concentrations in an Acidic Iron(II) Sulfate Solution: Potential Passive Treatment Substrates

Sandlin, Wes R.; Langman, Jeff B.; Waynant, Kristopher V.; Mukhopadhyay, Mausumi; Thuneman, Thomas; Moberly, James G.

doi:10.1007/s10230-020-00721-7

Cited by 2 publications

(5 citation statements)

References 46 publications

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“…The large variation of specific sorption values for replicate samples at pH 3.75 and 4.0 (Figure 2) likely is a result of a variable effect of Fe-(oxyhydr)oxide precipitation that increases the total Fe captured. The change in metal capture from primarily sorption to sorption + precipitation in this pH range was previously observed by the investigators (Sandlin, Langman, Waynant, et al, 2020) and is expected under these pH conditions because of the lower solubility of Fe in this pH range (Hem & Cropper, 1959). With precipitation of Fe (oxyhydr)oxides, there is a variable effect on Fe capture because of precipitated mineral formation, which increases the surface area for Fe sorption/precipitation (Smith, 1997).…”

Section: Batch Sorption Experimentssupporting

confidence: 58%

“…Zeolites within this intermediate range of Si/Al ratio are considered more stable and have greater heterogeneity in the porous crystal structure (Ramesh & Reddy, 2011). Iron sorption experiments with this Na-clinoptilolite have shown diffuse capture of Fe with no obvious patterns of Fe distribution across the grain surface suggestive of primary areas of mineral precipitation and growth (Sandlin, Langman, Waynant, et al, 2020). Prior to use in the sorption experiments, clinoptilolite grains were triple-rinsed with ultrapure (type I) water and dried at 80 ºC to remove weakly sorbed cations and dust generated during mining and handling.…”

Section: Zeolite: Clinoptilolitementioning

confidence: 94%

“…For this study, Naclinoptilolite grains of 2.4 to 4.8 mm in diameter (4 × 8 mesh) were obtained from KMI Zeolite, Inc. in Nevada, USA. This is a common grain size range for use in industrial applications (e.g., water filtration or mining reclamation) because of its ease of handling and packing stability (Sandlin, Langman, Waynant, et al, 2020). This Na-clinoptilolite (1.8% Na) has a surface area of 40 m 2 g −1 , is 66.7 wt.% SiO 2 and 11.5% Al 2 O 3 (Si/Al ratio of 5.8), and has a cation exchange capacity (CEC) of 1.6-2.0 meq/g (supplier certification, CAS #12173-10-3, ZeoFill certificate #ZEO-3722).…”

Section: Zeolite: Clinoptilolitementioning

confidence: 99%

“…Passive treatment systems may include reactive substrates such as limestone, biochar, or zeolites that induce metal sorption and/or mineral precipitation (metal capture) (Alcolea et al, 2012;Burakov et al, 2018;Costello, 2003;Johnson & Hallberg, 2005;Motsi et al, 2009;Obiri-Nyarko et al, 2014;Pandová et al, 2018;RoyChowdhury et al, 2015;Sandlin, Langman, Waynant, et al, 2020;Skousen et al, 2017). Solution acidity and proton competition for sorption sites determines the effectiveness of a reactive substrate for metal capture during passive treatment (Lee & Wilkin, 2010;Santomartino & Webb, 2007;Watzlaf et al, 2000;Ziemkiewicz et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…Solution acidity and proton competition for sorption sites determines the effectiveness of a reactive substrate for metal capture during passive treatment (Lee & Wilkin, 2010;Santomartino & Webb, 2007;Watzlaf et al, 2000;Ziemkiewicz et al, 1997). Zeolites have adsorption and ion-exchange properties that have proven effective for water treatment for neutral and mildly acidic solutions (Cabrera et al, 2005;Englert & Rubio, 2005;Merrikhpour & Jalali, 2013;Sandlin, Langman, Waynant, et al, 2020). Given the effectiveness of natural zeolites for water treatment (Margeta et al, 2013;Wang & Peng, 2010), their use as a reactive substrate has greatly expanded, such as removal of Cu, Pb, NH 4 ; reduction of salinity; and capture of antibiotics and organic micropollutants (Genç & Dogan, 2015;Jiang et al, 2018;Koshy & Singh, 2016;Wen et al, 2018;Xue et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Clinoptilolite and iron sorption/desorption under multiple pH conditions: Testing a substrate for passive treatment of acidic, iron‐rich solutions

Langman

Sandlin

Waynant

et al. 2021

Water Environment Research

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Equilibrium sorption and desorption experiments were conducted with clinoptilolite to evaluate the potential sorption/desorption of iron during different pH conditions. Sorption experiments indicated a partitioning of 0% to 17% of the iron in solution given pH of 2 to 4. The pH 2 solution was able to desorb 70% of the iron that was captured from a pH 3 solution. The largest desorption and sorption of iron and corresponding pH represent the end points of iron capture primarily by sorption/ exchange. These endpoints are the estimated pH pzc of 2.5 and the initial precipitation point of iron(II) at pH ~3.5. This acidity range is where clinoptilolite is able to capture iron without precipitation or the occurrence of full surface protonation. The inability of the highest acidity to remove all sorbed iron represents the greater bound iron that will not readily desorb with a change in pH. This retained iron creates a metastable state of the clinoptilolite that has a lower sorption capacity but reflects the ability of clinoptilolite to retain a sorbed transition metal with changes in pH. As pH varies, clinoptilolite may evolve in a sequence of metastable states reflective of its ability to capture or retain metals. © 2021 Water Environment Federation • Practitioner points• Clinoptilolite is a capable reactive substrate, but its sorption/exchange effectiveness at low and variable pH and ability to retain captured metals was unknown. • Clinoptilolite retains its metal capture properties to a pH of 2.5 where surface protonation and mineral degradation likely occurs. • The ability of clinoptilolite to retain captured iron under greater acidity reflects an evolution of its sorption/retention capacity.

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Section: Batch Sorption Experimentssupporting

confidence: 58%

Section: Zeolite: Clinoptilolitementioning

confidence: 94%

Section: Zeolite: Clinoptilolitementioning

confidence: 99%