Adsorption of heavy metals onto

Overview

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Key numbers

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through the carbonization of animal bones of different sources such 100% uptake of Cr(VI) ions at pH 1, initial Cr(VI) concentration of
efﬁciencies of the derived bone chars. Hence, researchers have metal ion in the range 60%–92%, indicating the effectiveness of the
structure on the bone char which is suitable for ions removal (C. K. exchange between the Ca2+ ions from the hydroxyapatite of the
surface area for removal of chemical pollutants. A composite of capability of the char by 143%. In the unary system, the study
component in bone char, by means of adsorption and ion precursor material for biosorption (Neolaka et al., 2023). As a
and above, the bone char is suitable for the sorption of the metal ions include: rice husks (Okoro et al., 2022), wheat bran (Ogata et al.,
concentration of 2 mg/L. The FTIR spectra indicated the due to the alterations and modiﬁcations done on the rice husks
was synthesized through an innovative route of microwave and signiﬁcantly increased sorption of Cu(II) ions from 90% to 97%
divalent ions of Pb, Cd, Cu, Zn for CRH were 54.3%, 8.24%, 51.4% of silica which enhances its adsorption properties. A recent study
and 56.7%, respectively while those for a similar dosage of ARH were synthesized varying zeolites from sugarcane bagasse ﬂy ash modiﬁed
74.04%, 43.4%, 70.08% and 77.2%, respectively (Nhapi, 2011). The with iron (III) oxide hydroxide. The resulting derived mesoporous
explored. This limits the applicability of the adsorbents in real efﬁciencies of Pb(II) ions from wastewater of higher than 82%.
Cu(II) ions attaining maximum of 90% removal, with Langmuir instance, a study was conducted by Ogata et al. (2014) to
results indicated that at the optimum conditions of pH 6, and recovery rate of approximately 100% for Cd(II) and 56% for lead
equilibrium time of 180 min the removal efﬁciency was 96.3%. (II), the lower rate for lead (II) indicates that the optimization of
in wastewater however, for broader applicability the incorporation removal of 51.0% and 90.0% for WB and M-WB, respectively. The
synthesized zeolites were tested for both batch and column 3.4 Fruit and vegetable waste
of Pb(II) and Cd(II) ions were reduced up to 90%. Langmuir derived from potato peels waste for the adsorption of Pb(II) ions.
particle diffusion model indicating that ﬁlm diffusion was the adsorbent attained a removal efﬁciency of 84% for Pb(II) ions within
dose of 1 g and a concentration of 50 mg/L of metal ions, the the adsorption mechanism of these adsorbents. Fruit peels have also
lemon peel powder as 72.5% and 71.3% for Pb(II) and Cu(II) ions, (Tien, 2018).
respectively and the orange peel powder as 56.7% and 34.5% for In another independent study, coffee husks were used for the
addition, it was observed that the hulls’ negative charge increased as adsorption process optimization revealed 99.65% maximum
that the coffee husks had 60% removal efﬁciency. Also, the FTIR 90% to 97%, similarly ARH exhibited an adsorption efﬁciency of
spectra revealed that the adsorption of Cr(VI) ions was enabled by 74% for Pb (II) ions compared to CRH (54%). The high silica
adsorption of 87% for Cr(VI) ions from aqueous solution by adsorption data of the metal ions on the rice husks-based adsorbents
thereafter raising concerns on the stability of material. In efﬁciency (>82%) for Pb(II). Similarly alkali activation of BFA
relatively low compared to other bio-sorbents such as activated adsorption efﬁciency was >90% in some studies the adsorption
content increased but only up to 50% (Abdel-Mohdy et al., 2005).
biosorption of the metals studied by chitin and the chitosan varied in chitosan coated on fabric was found to be at least 40% higher
acetamido groups (chitin and chitosan) from portunus sp to lead 4,057 mg/kg, respectively than the raw chitosan beads (CB)
(Pb2+). The crab shell was powdered, sieved, and added with lead (II) which possess the sorption capacity of 1,298 mg/kg with a
22%. It indicated that the acetamido group (chitin and chitosan) acts deacetylation of waste shrimp shell was studied for the removal
(Edokpayi et al., 2015) studied the synthesis and obtained of arsenic, nickel, and cobalt, was 98.50, 74.50, and 47.82%,
shells and its potential for Pb2+ removal from aqueous solution. The of chromium was 97.40% at pH 3. The calculated maximum
experiments were conducted in the range of 1–50 mg/L initial Pb2+ adsorption capacities of the chitosan for chromium, arsenic,
the potential for an average of 99% removal of Pb2+ from aqueous and two different degrees of deacetylation (DD) values of chitosan.
removal of lead and mercury was found to be above 80%, while the which has a higher DD value. According to the study, chitosan is a
of % extraction: Cu2+>Cd2+>Ni2+>Pb2+ (Khairkar and Raut, 2014). removal of the metal ions (Aderonke et al., 2014).
Cr6+was removed. For the case of crab chitosan, 80.91% maximum (pH, adsorbent dose, initial metal ion concentration) were
removal of Cr6+ was obtained whereas 73.89% maximum removal conducted by (Aydın and Aksoy, 2009). The maximum
concluded that keeping the amount of adsorbent and speed of 22.09 mgg-1 at pH 3, initial concentration of 30 mg/L and

Methods (brief)

studied. The process was found to follow pseudo second-order characteristics and the low-cost. Chitosan coated samples were
Efﬁcient removal of lead(II) ions from aqueous solutions using methyl-β-cyclodextrin

Implications

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised