Removal of lead ions from aqueous solutions by adsorption onto chemically modified silk cotton hulls by different oxidizing agents

Abstract

In the present study, the removal of lead ions from aqueous solutions was studied using activated carbons prepared from silk cotton hulls by three different acid activation methods; they are named as concentrated (conc.) H 2 SO 4 (AC), mixture of conc. H 2 SO 4 + H 2 O 2 (AC1), and mixture of conc.H 2 SO 4 + NH 4 S 2 O 8 (AC2). The surface properties of the adsorbent materials were determined by the Fourier Transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmette-Teller, scanning electron microscope, and energy dispersive X-ray analyses. From the thermogravimetric analysis result, the formation of carboxylic acid and lactones are present in the order AC2 > AC1 > AC. Brunauer-Emmette-Teller result shows that the activated carbons are macroporous in nature. Batch adsorption experiments were performed as a function of pH, adsorbent dose, contact time, initial metal ion concentration, and temperature. The experimental equilibrium adsorption data fits well for the Langmuir, Freundlich, and Tempkin equations. The maximum adsorption capacities were 40.00 mg g À1 for AC and 83.33 mg g À1 for AC1 and AC2, respectively. Adsorption kinetic data were modeled using the pseudo-first-order and pseudo-second-order, and intraparticle diffusion equations and its rate constants were evaluated. The adsorption process followed the pseudo-second-order reaction kinetics, suggesting that it is presumably chemisorption. The calculations of the thermodynamic parameters revealed that the adsorption process was endothermic, but it is feasible and spontaneous under natural conditions. The reversibility of the process has been studied in a qualitative manner, and it shows that the spent activated carbons can be effectively regenerated for further use easily. Figure 8. Kinetic fit for the adsorption of lead onto SCHACs at 30 C (a) pseudo-first order; (b) pseudo-second-order; and (c) intraparticle diffusion model. C. DULCY EVANGELIN, S. G. GUNASEKARAN AND M. DHARMENDIRAKUMARAsia-Pacific Journal of Chemical Engineering 198

Novel Silica‐Based Hybrid Adsorbents: Lead(II) Adsorption Isotherms

“…Consequently, the removal of lead(II) ions from water has turned out to be significantly important and highly urgent. To eliminate or reduce lead(II) pollution, various innovative approaches are designed and fabricated [ 2 , 4 – 6 ]. Among these approaches, hybrid materials or polymers with functionalized groups disclose excellent adsorption affinities for heavy-metal ions when they are used as the hybrid adsorbents [ 5 , 6 ].…”

Adsorption of lead(II) from aqueous solution using a poly(ethyleneimine)‐functionalized organic–inorganic hybrid silica prepared by hydrothermal‐assisted surface grafting method

“…In general, the data showed that adsorption capacity of Pb(II) ions on PEI‐functionalized hybrid silica by hydrothermal heating increased with increase in initial concentration of Pb(II) ions until 68.1 mg g −1 , which was 1.3 times as much as that by conventional heating (54.3 mg g −1 ) due to the improvement of grafting efficiency through reliable temperature and pressure control by hydrothermal heating. To access the performance of Pb(II) adsorption on PEI‐functionalized hybrid silica sorbent, the adsorption capacity had been compared with some reported data (Table ) …”

“…In the adsorption process, metal ions in the aqueous solutions may be transported through diffusion or convection to the surface of the sorbents and then become attached to the surfaces by various physical or chemical interactions. Sorbents with proper functional groups play the vital role in the adsorption performance . The chemical modification of silica gel has attracted certain attention as a sorbent to remove heavy metal ions from water or wastewater in recent years .…”