Experimental Investigation on Cadmium Ions Removal from Aqueous Solutions by Modified Wheat Straw Biosorbent

Background and Objactive: Cadmium is one of the heavy metals resulting from wastewater of different industries, and it is also highly toxic to human and the environment. So, the cations of this metal must be removed or reduced down to effluent standards. The aim of the current study was to investigate the cadmium removal efficiency by modified wheat straw from aqueous solutions.
In this study, wheat straw as the adsorbent was prepared in a laboratory scale and pulverized by standard ASTM sieves (40-120 mesh sizes). Consequently, wheat straw was functionalized by using NaOH solution with concentration of 0.7 M. FTIR analysis was used to characterize the functional groups in the prepared adsorbent. Adsorption process was accomplished in a batch laboratory-scale with emphasis on the effect of various parameters such as mesh size, pH, contact time, initial concentration of Cd (II), adsorbent dosage and mixing rate on the adsorption efficiency.
Findings: FTIR results showed that the modification of the wealth straw brought increase of stretch vibration band of hydroxyl and carboxyl groups. Optimized values for each factor to achieve the highest uptake were found to be as follows: the mesh size of 70, the contact time of 30 minutes, the initial concentration of 20 mg/L, the pH 7, the adsorbent dose of 1.5 g and the agitation speed of 240 rpm, at 25 ° C, respectively.
Discussion and Counclusion: The maximum removal efficiency of cadmium was found to be %98.5, at the optimized experimental condition. In general, results showed that the modified wheat straw as an unusable and cheap sorbent could be consider for the removal of the cadmium ion with nearly complete removal efficiency, at the optimized condition.