Removal and slow release studies of phosphate on surfactant loaded hydrothermally synthesized silicate nanoparticles

• Surfactant loading increases the phosphate adsorption capacity of silicate nanoparticles.
• Phosphate adsorption data fitted well with adsorption isotherm models.
• Maximum Langmuir monolayer phosphate adsorption capacity 93.46 mg g−1 is observed for HC.
• ΔG0, ΔH0 and ΔS0 values reveal the endothermic and spontaneous nature of process.

The reported work is mainly focused on the use of as-synthesized silicates (clinoptilolite and montmorillonite) nanoparticles and their surfactant modified forms for the removal and slow release formulation of phosphate. Batch experiments have been carried out to determine the influence of parameters like initial phosphate concentration, pH of the medium, contact time between the adsorbate and adsorbent, weight of adsorbent, and system temperature on phosphate removal. Furthermore, slow phosphate release studies have been performed by thin layer-funnel analytical test and soil column percolating system. The results of batch adsorption studies reveal that surfactant modified forms of clinoptilolite and montmorillonite show better adsorption potential for phosphate than their unmodified form and phosphate removal ability of surfactant modified silicates increases with increasing amount of loaded surfactant. The maximum adsorption of phosphate is observed around pH 7 and maximum Langmuir monolayer phosphate adsorption capacity 93.46 mg g−1 is observed for hexadecyltrimethylammonium (CH3(CH2)15N+(CH3)3) loaded clinoptilolite (HC). The obtained results indicate that surfactant loaded silicates are very good adsorbent for phosphate removal and slow release of phosphate is also achievable as it releases phosphate still after 15 days of leaching.