K. Kadirvelu

Chromium(VI) removal from aqueous system using Helianthus annuus (sunflower) stem waste.

The objective of this study was to investigate the Cr(VI) removal efficiency of sunflower waste from aqueous system under different process conditions. Two adsorbents were prepared by pre-treating the sunflower stem waste. One adsorbent was prepared by boiling it and second adsorbent was prepared by treating it with formaldehyde. Batch mode experiments were carried out as a function of solution pH, adsorbent dosage, Cr(VI) concentration and contact time. FT-IR spectra and SEMs of the adsorbents were recorded to explore the number and position of functional groups available for the binding of Cr(VI) ions and morphology of the studied adsorbents. The removal of chromium was dependent on the physico-chemical characteristics of the adsorbent, adsorbate concentration and other studied process parameters. Maximum metal removal was observed at pH 2.0. The efficiencies of boiled sunflower stem absorbent and formaldehyde-treated sunflower stem absorbent for the removal of Cr(VI) were 81.7 and 76.5%, respectively for dilute solutions at 4.0g/L adsorbent dose. The applicability of Langmuir, Freundlich and Dubinin-Radushkevich isotherms was also tested. The results revealed that the hexavalent chromium is considerably adsorbed on sunflower stem and it could be an economical method for the removal of hexavalent chromium from aqueous systems.

Adsorption of hexavalent chromium from aqueous medium onto carbonaceous adsorbents prepared from waste biomass.

This paper reports the adsorption of Cr(VI) ions from aqueous solution by sulphuric acid treated sunflower waste. Two adsorbents, namely SHC and SSC, were prepared from sunflower plant head and stem waste. The adsorbents were characterized by FT-IR, SEM and EDX. The surface areas of SHC and SSC were 1.17 and 1.28 m(2)g(-1), respectively. The effect of various process parameters namely pH, temperature, initial metal ion concentration, adsorbent dosage and contact time has been studied. The optimum conditions for removal of Cr (VI) were found to be pH=2, contact time=2h, adsorbent dosage=4.0 g/L, concentration=250 mg/L, temperature=25+/-1 degrees C, rpm=180. The percent removal at these optimum conditions was found to be 75.7% and 85.4% for SHC and SSC respectively. The Freundlich, Langmuir and D-R models were applied for mathematical description of adsorption equilibrium. Adsorption data were well described by the Langmuir isotherm with maximum adsorption capacities of 53.76 mg/g and 56.49 mg/g for SHC and SSC, respectively. Overall, the experimental results suggest that SHC and SSC could be used as low cost alternative adsorbents for the treatment of Cr(VI) containing wastewater. A comparison of different kinetic models showed that our data fitted well to the pseudo-second order model.

Investigation of Cr(VI) adsorption onto chemically treated Helianthus annuus: Optimization using Response Surface Methodology

In the present study, chemically treated Helianthus annuus flowers (SHC) were used to optimize the removal efficiency for Cr(VI) by applying Response Surface Methodological approach. The surface structure of SHC was analyzed by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Analysis (EDX). Batch mode experiments were also carried out to assess the adsorption equilibrium in aqueous solution. The adsorption capacity (qe) was found to be 7.2 mg/g. The effect of three parameters, that is pH of the solution (2.0-7.0), initial concentration (10-70 mg/L) and adsorbent dose (0.05-0.5 g/100 mL) was studied for the removal of Cr(VI) by SHC. Box-Behnken model was used as an experimental design. The optimum pH, adsorbent dose and initial Cr(VI) concentration were found to be 2.0, 5.0 g/L and 40 mg/L, respectively. Under these conditions, removal efficiency of Cr(VI) was found to be 90.8%.

Equilibrium and kinetic studies for sequestration of Cr(VI) from simulated wastewater using sunflower waste biomass.

In the present work, potential of sunflower head (BSH) [an agricultural waste biomass] to remove Cr(VI) from simulated wastewater has been evaluated under different process conditions such as pH, metal concentration, adsorbent dose and contact time. A contact time of 120 min and pH 2.0 were found to be optimum. Chromium removal decreased from 90.0 to 45.2% as its concentration increased from 10 to 70 mg/L. The Cr(VI) removal increased from 31.4 to 52.4% as adsorbent dose increased from 4.0 to 20.0 g/L using a test solution having 100mg/L Cr(VI) concentration. Adsorption isotherms were employed to evaluate the maximum adsorption capacity. Adsorption data fitted well to Langmuir isotherm and pseudo-second order model as indicated by high values of correlation coefficient (0.9882 and 0.999) respectively. The adsorption capacity calculated from Langmuir isotherm was 8.177 mg/g.

Chromium Removal from Aqueous System and Industrial Wastewater by Agricultural Wastes

ABSTRACT This study involved the development of formaldehyde-treated, deseeded sunflower head waste–based biosorbent (FSH) for the biosorption of Cr(VI) from aqueous solution and industrial wastewater. Batch-mode experiments were conducted to determine the kinetics, sorption isotherms, effect of pH, initial Cr(VI) concentration, biosorbent dose, and contact time. The results demonstrated that FSH can sequester Cr(VI) from the aqueous solution. The maximum sorption occurred at pH = 2.0, biosorbent dose = 4.0 g/L, concentration of 100 mg/L at 25°C at 180 rpm after 2 h contact time. The FSH had an adsorption capacity of 7.85 mg/g for Cr(VI) removal at pH 2.0. The rate of adsorption was rapid, and equilibrium was attained within 2 h. The equilibrium sorption data fitted the Langmuir isotherm model, which was further confirmed by the chi-square test.

Competitive Sorption of Cu(II), Pb(II) and Hg(II) Ions from Aqueous Solution Using Coconut Shell-based Activated Carbon

Many adsorbents have been studied for their adsorption properties towards one-component metal ion solutions. However, if these materials are to be used for treating wastewater, their performance has to be determined in multi-component solutions. In the present work, multi-component metal sorption by coconut shell-based activated carbon has been studied using single, binary and ternary systems composed of Cu(II), Pb(II) and Hg(II) ions. The influence of solution pH was also demonstrated. A set of desorption studies was also performed for the same metal ions with the aim of investigating the mechanism involved. It was found that chemisorption, surface chelation and complexation might be a possible metal ion removal mechanism. Scanning electron micrographs (SEM) and the EDAX spectrum of the activated carbon surface before and after equilibration of the adsorbent with the metal ion solution clearly showed the presence of Cu(II), Pb(II) and Hg(II) ions. An attempt was made to quantify the interaction behaviour of the metal ion on the adsorbent and to correlate such observations with the chemical and physical properties of the metal ions. The ability of isotherm models such as those of Freundlich and Langmuir to predict the equilibrium uptake of Cu(II), Pb(II) and Hg(II) ions from one-component, binary and ternary systems was also tested. Both the Langmuir and Freundlich models were found to fit the experimental data well. The applicability of the extended Langmuir model was also evaluated for multi-component systems.

Mercury (II) removal from water by coconut shell based activated carbon: Batch and column studies

Abstract This study was undertaken to investigate adsorption behavior of Hg (II) from aqueous systems on activated carbon in static and dynamic mode by varying initial Hg (II) concentration, adsorbent dose and pH. Langmuir and Freundlich adsorption isotherm were applied to model the adsorption data. Removal of mercury obeyed the Langmuir and Freundlich adsorption isotherm models. The extent of removal of Hg (II) was found to be dependent on sorbent dose, pH and initial Hg (II) concentration. Mercury uptake increased from 72 to 100 percent with increasing pH from 2 to 10. A set of desorption studies was also performed for the metal ions with the aim of investigating the mechanism involved. Moreover, the competing effects of various ions like Pb (II) and Cu (II) is also described. The column capacity for a column diameter of 20 mm, bed height of 0.4 m, hydraulic loading rate of 7.5 m3h‐1m‐2 and a feed concentration of 3 mg I‐1 were found to be 3.02 mg g‐1. Breakthrough curves were plotted for the adsorption of mercury on the adsorbent using continuous‐flow column operation by varying different operating parameters like hydraulic loading rate (3–10.5 m3h‐1m‐2), bed height (0.3–0.5 m), and feed concentrations (2–6 mg I‐1). The aim was to assess the effect of bed height, hydraulic loading rate and initial feed concentration on breakthrough time and adsorption capacity, which helped in ascertaining the practical applicability of the adsorbent. At the end an attempt has been made to develop empirical relationship from the data generated from column studies for designing the adsorption column, based on the Bohart ‐Adams model.

Removal of Ni(II) from aqueous system by chemically modified sunflower biomass

AbstractThis study reports the removal of Ni(II) onto boiled sunflower head (BSH) and formaldehyde sunflower head (FSH) adsorbents by batch technique. The adsorbents were characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. The results showed that Ni(II) adsorption was dependent on process operating conditions including pH of the solution, adsorbent dosage, temperature, and initial Ni(II) ion concentration in the solution. The optimum pH for Ni(II) was 6.0. Maximum nickel adsorption was 65.5 and 75.9%, respectively, by BSH and FSH at adsorbent dose = 20.0 g/L, initial Ni(II) concentration = 100 mg/L, temperature = 25 ± 1°C. Langmuir and Freundlich isotherm models were used to analyze the equilibrium adsorption data. Freundlich isotherm fitted the data well with R2 values >0.99 for both the adsorbents. The results also showed that pseudo-second-order kinetic model correlated well with the adsorption data with R2 val...

A pilot scale evaluation for adsorptive removal of lead (II) using treated granular activated carbon.

Wastewaters discharged from the defence serviceable industries pose a serious environmental hazard due to their heavy metal load. The present study focused on optimizing the operational variables viz, hydraulic loading rate, bed height and feed concentration through bench scale study and using that for assessing the efficiency of pilot scale system with sulphur loaded carbon (AC-S) as the adsorbent in the removal of Pb (II). Static mode adsorption studies were also carried out for Pb (II) removal using treated (AC-S) and untreated carbon (AC). AC-S shows about 35 percent increase in maximum adsorption capacity over that on AC. The maximum adsorption capacity in the column mode for Pb (II) at the optimized conditions: bed height of 0.4 m, hydraulic loading rate of 7.5 m3h−1m−2 and the feed concentration of 6 mg l−1 for achieving 50 % breakthrough concentration was found to be 2.89 mg g−1. Adsorption mechanism involved during Pb (II) in the column has also been explored. Bohart - Adams model was used for modeling the bench scale data and predicting the adsorption behavior at pilot scale level.