Adsorption behavior of rice husk for the decontamination of chromium from industrial effluents

Abstract

Rice husk, an agricultural waste product, was studied as a potential decontaminant for chromium in the effluents of leather tanning industries. Physico-chemical parameters such as selection of appropriate electrolyte, shaking time, concentration of adsorbent and adsorbate were studied to optimize the best conditions in which this material can be utilized on commercial scale for the decontamination of effluents.The radiotracer technique was used to determine the distribution of chromium. In certain cases atomic absorption spectrophotometry was also employed. Maximum adsorption was observed at 0.01 mol-dm -3 acid solutions (HNO 3, HCI, H2SO 4 and HCIO4) using 3.0g of adsorbent for 2.73 -I 0 -3 mol-dm -3 chromium concentration in five minutes equilibration time. Studies show that the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the range of 2.73.10 -3 to 2.73.10 -2 tool dm -~ chromium concentration. The characteristic Freundlich constants, i.e., 1/n = 0.86+0.06 and A = 2.35_+0.06 mmol .g-~ have been computed for the sorption system. Thermodynamic parameters, i.e., AG ~ AS ~ and AH ~ have also been calculated for the system. Application of the method to a test case of a medium size industry showed that 21 kg of rice husk was sufficient to maintain the NEQS limits of chromium for industrial effluents.

Sawdust: Cost Effective Scavenger for the Removal of Chromium(III) Ions from Aqueous Solutions

“…It is clear from the results that maximum sorption occurred in deionized water while the sorption decreased with an increase in acid concentration. These results are in conformity with Hg (II) ions sorption onto sawdust (Hasany and Ahmad, 2002) and coconut husk and chromium onto rice husk (Khalid et al, 1999). The decrease in chromium sorption at higher acid concentration might be due to the competition of the proton and the positively charged chromium ions.…”

“…Chromium, an important element from environmental point of view has been the subject of several studies wherein its accumulation on cheaper materials like flyashwollastonite (Pandy et al, 1984), zeolites (Foldesova et al, 2000), modified coconut husk (Low et al, 1997), rice husk (Khalid et al, 1999), Haro river sand (Hasany and Chaudhry, 1998), seed of leguminous crops (Voropanova et al, 1998) and modified rice husks (Lee et al, 1998) have been investigated. Chromium pollution is a serious problem facing our country due to the tannery industry.…”

Chemically Modified Rice Husk Adsorbents, Characterization and Removal of Palladium(II) From Aqueous Solutions

“…RH exhibited highest adsorption capacity at pH 5.0. Similar tend was reported by Khalid et al [34] while employing rice husk as an adsorbent for chromium. The results demonstrated that the maximum adsorption capacity for RH occurred at pH 5.0, pH 2.0 was found optimum for Pd(II) ions adsorption on RHS-ED and RHS-DT while RHS exhibits maximum capacity at pH 2.5.…”

Removal of copper ions from aqueous solution using silica derived from rice straw: comparison with activated charcoal

“…In the present study, the decrease in the sorption of copper at higher acidic medium can be explained on the basic of competitive reaction of the protons in the medium and positively charged copper(II) ions. While small sorption of metal at low pH is in accordance with the concept of zero point charge (pHzpc) which lies in the range of 1.8-2.2 for SiO 2 (Khalid et al 1999). Also the sample may contain other organic compounds in Si-sample which the sorption may be due to the electrostatic attraction with the surface groups.…”

“…This results in the formation of silica surface as weakly acidic. The cation exchange reaction can occur in aqueous solution as follows (Khalid et al 1999):…”