Adsorption of Zn2+ and Ni2+ in a binary aqueous solution by biosorbents derived from sawdust and water hyacinth (Eichhornia crassipes)

Abstract

The Zn(2+) and Ni(2+) adsorption capacities of six biosorbents derived from water hyacinth (Eichhornia crassipes) (WH) and sawdust (SD) were investigated, with activated carbon as the control. The biosorbents were raw biomass (WH, SD), charred WH (BWH) and SD and sulphonated bio-chars of WH and SD. The effect of the initial solution pH and Zn(2+) and Ni(2+) concentrations on adsorption capacity was studied, and adsorption isotherms for Zn(2+) and Ni(2+) evaluated. The initial solution pH significantly influenced adsorption (p < 0.05) but the relationship was generally nonlinear. Zn(2+) suppressed Ni(2+) adsorption on all biosorbents. The adsorption capacities of the biosorbents were statistically (p ≤ 0.05) similar to or higher than that of activated carbon. The effects of pyrolysis and bio-char sulphonation on adsorption were inconsistent and dependent on biomass type; in most cases bio-char was a better biosorbent than the original biomass, while sulphonation resulted in less or comparable adsorption. Adsorption data obeyed at least one of three isotherms (linear, Langmuir and Freundlich) (r(2) = 0.90-0.995, p < 0.05). The study revealed that low-cost biosorbents may be used as alternatives to activated carbon in applications including selective separation of Zn(2+) from multi-metal ion solutions containing Ni(2+), and water and wastewater treatment.

Removal of Zn 2+ and Pb 2+ ions from aqueous solution using sulphonated waste polystyrene

“…Adsorption data following the Langmuir model indicate homogeneous monolayer or surface adsorption of Zn 2+ and Pb 2+ on the SWPS resins, while those that followed the Freundlich isotherm model suggest multilayer adsorption or the occurrence of both surface and intra-particle diffusion. Similar behaviour has been reported for sulphonated biochar [18]. This confirms the insertion of sulphonic groups, which improve the adsorption capacity of the waste polystyrene.…”

“…This suggests sulphonated EPS has a higher concentration of inorganics, this could account for the lower adsorption capacity for both Pb 2+ and Zn 2+ . Both these EC values were however, lower than those of biosorbents derived from water hyacinth and sawdust which were in the ranges 103-173.2 and 2.3-3.9 mS/m respectively [18]. The water content of sulphonated HIPS is slightly higher (about 5.79%) than that of sulphonated EPS.…”

“…The adsorption data followed both Langmuir and Freundlich isotherm models suggesting multilayer adsorption or the occurrence of both surface and intra-particle diffusion [18]. WPS showed no heavy metal adsorption capacity.…”

“…Both sulphonated HIPS and sulphonated EPS were alkaline with pH values of 9.45 and 9.95, respectively (Table 1). Activated carbons have pH in the region 3.9-4.3 [18]. The respective EC values were remarkably different at 376.7 and 1493.3 mS/m respectively.…”

Simultaneous adsorption behavior of heavy metals onto microporous olive stones activated carbon: analysis of metal interactions

“…Gwenzi et al (2014) also found that the affinity order Cd(II) [ Cu(II) found in mono solute solutions changed to Cu(II) [ Cd(II) when the metals were forming binary mixtures. As seen in Table 6, the sum of the maximum adsorption values of both metals in binary mixtures (q max , tot ) is in most of the cases less than the sum of those in single solutions indicating that the joined effect on each other metal is antagonistic.…”