Removal and enrichment of Cr(VI) from aqueous solutions by lotus seed pods

Abstract

Chromium (Cr(VI)) is highly toxic and carcinogenic. Cr(VI) water pollution has become more and more serious. This article reports on a study in which lotus seed pods (LSP), an agricultural waste product, was used to efficiently remove Cr(VI) from an aqueous solution, and the carbonization product of LSP after the removal of Cr(VI) (CPLSP) can be regarded as a resource containing Cr. Cr(VI) removed by LSP fits a pseudo-second-order model. pH levels greatly influence the amount of Cr removed. The maximum removal of Cr(VI) by LSP in aqueous solution was 153.85 mg/g. The possible removal mechanism is absorption, redox, and reabsorption based upon SEM/EDS, FT-IR, and XPS spectra results. The Cr content of CPLSP was 42.95% by ammonium persulfate oxidation titrimetric method. These results suggest that LSP can be an excellent, low cost, biomaterial for removing and enriching Cr(VI) from an aqueous solution. • Practitioner points• Lotus seed pods are an efficient adsorbent for Cr(VI) from aqueous solutions. • The Cr removal by lotus seed pods occurs via absorption, redox, and reabsorption. • Cr can be captured after the pods are carbonized. • Lotus seed pods can be applied to the removal and enrichment of Cr(VI) from waste water.• Key words adsorption mechanism; biomaterials; CPLSP; Cr(VI); enrichment; lotus seed pods; LSP; the carbonization product of LSP after the removal of Cr(VI); wastewater

Estimation of Model Parameters in the Extraction of Cr(VI) from Wastewater by an Emulsion Liquid Membrane

“…In the membrane phase, the transport rate and concentration of Cr(VI) ions accumulated in carrier rises as expected. Between K e and K s values, the apparent rates remained constant, while the maximum Cr(VI) ion accumulation in the liquid membrane phase C LM * increased from 0.73 to 0.8 as the D2EHPA concentration increased from 5 to 15 vol %, respectively 14.…”

“…At the membrane phase level, both the transit rate and the concentration of Cr(VI) increase as expected with increasing pH of the stripping phase. The apparent constants K e and K s , as well as the maximum Cr(VI) ion accumulation in the liquid membrane phase C LM *, are constant in the test, with the greatest increase (0.69 to 0.83) for an increase in the external‐phase pH from 1 to 3, respectively 14.…”

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