Release of lead from Pb-clinoptilolite: managing the fate of an exhausted exchanger

Brundu, Antonio; Cerri, Guido

doi:10.1007/s13762-016-1149-2

Cited by 7 publications

(5 citation statements)

References 35 publications

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“…The beneficiation process enabled a powder to be obtained with a clinoptilolite content of about 89 wt %, along with residual amounts of feldspars, glass, opal-CT, biotite, and quartz. This result confirms that the beneficiation process here adopted is effective and replicable [20,22,29,30]. The high ammonium content (2.21 meq/g), along with the low sodium, potassium, calcium, and magnesium contents, indicate that a near end-member of NH 4 -clinoptilolite was obtained.…”

Section: Resultssupporting

confidence: 77%

“…The nucleation of cristobalite from thermally treated zeolites is not a novelty [22,23,35] but, so far, it has never been reported for NH 4 -clinoptilolite. An analogous consideration applies to mullite; in fact, literature reports the thermal transformation of NH 4 -exchanged synthetic zeolites to mullite [12,13], but this phase has never been obtained from natural zeolites.…”

Section: Discussionmentioning

confidence: 95%

“…Hence, the percentage of mullite (impure) could be slightly higher than the amount calculated on the basis of the theoretical formula Al 6 Si 2 O 13 . Moreover, crystalline phases, having formulae that deviate from ideal compositions, were already obtained by thermal treatment of synthetic zeolites [39] or clinoptilolite [21,22].…”

Section: Discussionmentioning

confidence: 99%

“…The rock was subjected to the beneficiation process described in previous papers [20,22,29,30], aimed to increase the zeolite content. Briefly, the material was submitted to autogenous comminution and dry sieving.…”

Section: Starting Materials and Beneficiation Processmentioning

confidence: 99%

“…The use of natural zeolites in ceramic production has been evaluated by different research groups, highlighting the advantages, generally a lowering of sintering temperatures and limits, mainly linked to the dark color often observed in the fired products [15][16][17][18][19]. Recent papers show that crystalline materials can be obtained by thermally induced transformation of Cs-and Pb-exchanged clinoptilolite [20][21][22], whereas only an amorphous phase has been achieved from the thermal treatment of a NH 4 -clinoptilolite [23].…”

Section: Introductionmentioning

confidence: 99%

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Thermal Transformation of NH4-Clinoptilolite to Mullite and Silica Polymorphs

2017

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Clinoptilolite is a natural zeolite used for the abatement of ammonium in the treatment of urban wastewater. By considering that mullite was obtained through thermal treatment of NH 4 -exchanged synthetic zeolites, this work aimed to evaluate if this phase can be obtained from NH 4 -clinoptilolite. A material containing about 90 wt % of clinoptilolite, prepared using a Sardinian zeolite-rich rock, was NH 4 -exchanged and subjected to treatments up to 1200 • C. After dehydration, de-ammoniation, and dehydroxylation processes, the clinoptilolite structure collapsed at 600 • C. An association of mullite, silica polymorphs, and glass, whitish in color, was obtained for treatments between 1000 and 1200 • C. The higher degree of crystallinity was reached after a 32 h heating at 1100 • C: mullite 22 wt %, cristobalite 59 wt %, tridymite 10 wt %, glass 9 wt %. It is possible to speed up the kinetics of the transformation by increasing the temperature to 1200 • C, obtaining the same amount of mullite in 2 h, but increasing the residual amorphous fraction (16 wt %). These results indicate that NH 4 -clinoptilolite could represent a raw material of potential interest in the ceramic field, in particular in the production of acid refractory, opening scenarios for a possible reuse of clinoptilolite-based exchangers employed in ammonium decontamination.

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Section: Resultssupporting

confidence: 77%