Abstract
In the present work, the hydroxyapatite/alginate nano-composite adsorbent was prepared by incorporating nano-sized hydroxyapatite (nHAp) into alginate polymer and uses this adsorbent for removal of nitrate from groundwater. The synthesized nano-composite and pure alginate as well as the pure hydroxyapatite were characterized with Fourier Transform Infrared (FT-IR) spectroscopy to ascertain the functional groups. The adsorption characteristics of nitrate from groundwater on the HAp/Alg nano-composite were optimized under different operational parameters like contact time, pH, adsorbent dosage, initial concentration of nitrate and temperature in batch system. Maximum equilibrium capacity reached 99% of nitrate removal by using the HAp/Alg nano-composite after 240min at pH 3; adsorbent dosage, 2g; initial concentration, 100mg/l and temperature, 20°C. The kinetics studies revealed that the pseudo-second-order kinetic model was able to describe the dynamic behavior of the adsorption process by composite adsorbents used in this work. Also, the Langmuir isotherm model is very well fitted to the equilibrium data. The mechanism of NO3- ions adsorption by the nano-composite adsorbent was described. So, it is concluded that HAp/Alg nano-composite is a relatively efficient and low cost as well as the results validated the feasibility of HAp/Alg nano-composite for highly effective removal of nitrate from an aqueous solution.
Highlights
Assiut governorate, one of the oldest governorates of Upper Egypt, It extends south-north between Sohag and ElMinya governorates from latitude 26° 47' N to 27° 37' N and extends west-east between New Valley and Red Sea governorates from longitudes 30° 37' E to 31° 34' E (Figure 1)
This study demonstrated how the nano-sized hydroxyapatite (nHAp)/Alg nanocomposite prepared and employed for the removal of nitrate ions from groundwater in a batch method, can be used as a more effective adsorbent in use
Maximum equilibrium capacity is 99% of nitrate removal was obtained using the HAp/Alg nano-composite after 240min; at pH, 3; adsorbent dosage, 2g, initial concentration, 100mg/l and temperature 20°C
Summary
One of the oldest governorates of Upper Egypt, It extends south-north between Sohag and ElMinya governorates from latitude 26° 47' N to 27° 37' N and extends west-east between New Valley and Red Sea governorates from longitudes 30° 37' E to 31° 34' E (Figure 1). Groundwater is deemed one of the major resources for potable water in Assiut governorate especially in rural areas (ALDAR, 2011). In this study, selected samples of groundwater were collected and chemically analyzed Analysis of these samples (Table 1) revealed that they have nitrate concentrations more than the maximum permissible limit recommended (50mg/l) by WHO, 2011. This is due its high solubility in water and this is manifested by Hekmatzadeh et al, 2012, who state that due to its high solubility, nitrate is the most likely cause of the contamination in groundwater across the globe, and a potential threat to water resource, as well as increasing eutrophication
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