Removal of Heavy Metals from Aqueous Solutions using Zeolite(LTA) Synthesized from Sudanese Clay

Abstract

Abstract This study was carried out to synthesize zeolite LTA from Sudanese clay, from the banks of the Blue Nile in Bahary province. The clay was purified and analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Fluorence (XRF) methods. The results of the chemical analysis showed that the starting material (clay) is montmorillonite . Also those results showed that four types of zeolite were successfully synthesized (Vauxite, Alunite zeolite A and zeolite LTA) .The controlled conditions used were (440, 550, 650 and 750 oC and 1h) for the clay calcination, 100oC and 2h for the reaction, 12h for formation of zeolite crystals and 5 M NaOH for the alkali concentration. The differences in zeolite types is due to different temperatures of calcination of the clay. The results indicated that zeolite LTA was the best synthesized sample. To determine the most effective zeolite sample, the samples have been tested for the removal of lead ion (10 mg/l) from aqueous solution. The concentration of lead was measured before and after treatment using Inductively Coupled Plasma. The analysis showed that zeolite LTA was the best in the removal of lead with 99.42%, followed by zeolite A 81.22%, Alunite 73.14% and Vauxite 63.14%. On this basis zeolite LTA was chosen as the best sample for use in the removal of heavy metals from aqueous solutions. The factors affecting the removal of ions such as dose of zeolite LTA, time, initial concentration as well as pH were studied. The results showed that zeolite LTA is very effective for removal of tested ions(Pb2+ , Zn2+, Cu2+ , Ni2+) from aqueous solutions, and the removal percent at the first 30min. was high . It was found that the effectiveness of zeolite LTA continued for two hours and then the zeolite was saturated and lost the ability to remove heavy metal ions from aqueous solution. The results indicated that, with the increase of pH (from 1 to 5) the efficiency of zeolite in removal of those ions increased. The percentage of the elimination efficiency of zeolite ranged from 72.2% to 99.42% for Pb2+, iv from 35.28% to 98.93% for Zn2+, from 85.6% to 94.97% for Cu2+ and from 12.45% to 73.14% for Ni2. Zeolite LTA was activated after losing its ability to remove the adsorded heavy metal ions with sodium chloride solution (1M), and then it was tested for effectiveness in removal of heavy metals ions. It was found that zeolite LTA after regeneration well removed the heavy metals ions, but in less degree than the fresh zeolite LTA shortly before activation. To compare the effectiveness of synthesized zeolite LTA, before and after activation and montmorillonite, their ability was tested with solution of the Pb2+ (10mg/l) for 30min. It was found that zeolite LTA is the best sample in the removal of Pb2+ with the rate of 99.42%, followed by regenerated zeolite LTA with rate of 98.92% and finally montmorillonite with the rate of 55.44%.