Abstract
In this study, adsorption of zinc onto the adsorbent (untreated rice husk and NaOH-treated rice husk) was examined. During the removal process, batch technique was used, and the effects of pH and contact time were investigated. Langmuir isotherm was applied in order to determine the efficiency of NaOH-treated rice husk used as an adsorbent. The zinc adsorption was fast, and equilibrium was attained within 30 min. The maximum removal ratios of zinc for untreated rice husk and NaOH-treated rice husk after 1.5 h were 52.3% and 95.2%, respectively, with initial zinc concentration of 25 mg/L and optimum pH of 4.0. Data obtained from batch adsorption experiments fitted well with the Langmuir isotherm model. Maximum adsorption capacity of zinc onto untreated rice husk and NaOH-treated rice husk was 12.41 mg/g, and 20.08 mg/g respectively, at adsorbent dosage of 1 g/L at 25°C. The nature of functional groups (i.e., amino, carboxyl, and hydroxyl) and metal ion interactions was examined by the FT-IR technique. It was concluded that the NaOH-treated rice husk had stronger adsorption capacity for Zn2+ compared with the untreated rice husk. The NaOH-treated rice husk is an inexpensive and environmentally friendly adsorbent for Zn2+ removal from aqueous solutions.
Highlights
The environmental pollution due to toxic heavy metals is spreading through the world along with industrial progress [1]
Many studies have shown that pH is an important factor affecting absorption of heavy metals [13, 14]
Absorption increased with increasing solution pH since more metal binding sites could be exposed with negative charges, with subsequent attraction of metal ions with positive charges and absorption occurring onto the cell surface [15]
Summary
The environmental pollution due to toxic heavy metals is spreading through the world along with industrial progress [1]. Zinc is an ubiquitous metal ion in soil and aquatic environments. At background levels, it is an important nutrient, but at elevated concentrations due to anthropogenic processes, zinc becomes toxic. Active carbon adsorption was considered to be common and effective, but the cost is high [7]. For this reason, many studies have been carried out in order to find out effective and low-cost adsorbents. Rice husk (as an agricultural waste) has a large quantity of production and is evaluated as an appropriate adsorbent due to its low-cost and high removal efficiency
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
