Novel adsorbent based on silkworm chrysalides for removal of heavy metals from wastewaters

In this contribution, maximum capacity for adsorption of Pb2+, Ni2+, and Cu2+ by silkworm chrysalides (SC) was determined. The raw silkworm chrysalides (SCr) and chrysalides after acidic washing (SCw) were used. Chitin (CT), extracted from SC, and chitosan (CS), with 85% deacetylation, were employed as reference samples. Adsorption tests showed that all the studied adsorbents exhibited excellent performance in removal of metals. The choice of a more appropriate adsorbent is related to its efficiency for removal of a specific metal. The studied materials presented different intensities for metal adsorption as follows: (i) Ni2+ > Cu2+ > Pb2+ for SCr; (ii) Pb2+ > Cu2+ > Ni2+ for SCw; (iii) Ni2+ > Cu2+ > Pb2+ for CT; and (iv) Cu2+ > Pb2+ > Ni2+ for CS. Metal adsorption onto SCr and CS was analyzed by Freundlich and Langmuir isotherm equations. Adsorption values for CS–Pb and SCr–Ni were provided by the Freundlich model, while the adsorption values for CS–Cu, CS–Ni, SCr–Pb, and SCr–Cu were provided by the Langmuir model. The studied adsorbents are suitable for use in treatment of wastewater. From the economic point of view, the use of SCr as an adsorbent of heavy metals (mainly Ni2+) on the large industrial scale would be more appropriate.