KINETICS AND ADSORPTION POTENTIAL OF AMBO SANDSTONE FOR THE REMOVAL OF PHOSPHATE FROM AQUEOUS SOLUTION

Abstract

P h o s p h o r u s p l a y s a n e s s e n t i a l r o l e i n t h e d e v e l o p m e n t o f o r g a n i s m s . However, p hosphorus pollution known as eutrophication is regarded as one of the main causes of water quality deteria ra tion . Therefore, the decontamination of phosphorus from aqueous solution i s necessary. Thus this study was conducted to investigate the potential of Ambo sandstone a s a n a d s o r b e n t. B a t c h a d s o r p t i o n e x p e r i m e n t w a s c o n d u c t e d a n d t h e following results were found . The analysis of the stone using SEM was indicated that the stone had a wide range of grain sizes from coarse, medium to fine ones. Whereas the analysis of the Ambo sandstone using XRD revealed that the stone was maily composed of quartz (SiO2) followed by different oxides,such as MgO, CoO and CdO. The optimum values for the studied parameters were: pH = 3, agitation speed = 120 rpm, dose = 0.05 g, contact time = 16 hr and initial phosphate concentration = 30 mg/L. Among different particle size (0.25, 0.3 and 0.75 mm) used, the smallest particle size showed the highest adsorption efficiency (86.46%). pHzpc was found to be 6.3. All the tested anions were found to interfere with phosphate adsorption, especially fluoride ion highly affect adsorption.. The desorption efficiency was small (22%) which indicates chemisorptions was involved. The Freundlich model was well fitted for experimental equilibrium data (R2 = 0.979). The kinetic adsorption process was better correlate with pseudo-second–order model (R2 = 0.996). The thermodynamic study parameters indicated that the adsorption process was endothermic and spontaneous. The maximum adsorption efficiency was 84.3% and the maximum adsorption capacity was 21.2 mg/g. Therefore, the sandstone is a promising adsorbent for removal of phosphate from aqueous solution.