Highly efficient adsorption of ammonium onto palygorskite nanocomposite and evaluation of its recovery as a multifunctional slow-release fertilizer

• One-step in situ grafted polymerization synthesis of palygorskite nanocomposites.
• The palygorskite nanocomposite exhibited excellent adsorption property for NH4+.
• Various adsorption models were applied to study the adsorption mechanism.
• The nitrogenous adsorbent could be used as a multifunctional slow-release fertilizer.

With the aim of minimizing the negative impact of nitrogen pollution and improving fertilizer use efficiency, a novel palygorskite (PGS) nanocomposite adsorbent was prepared, characterized and used for removal and recovery of NH4+ from ammonium wastewater with the agronomic reuse as a multifunctional slow-release ammonium fertilizer (MSAF). Batch adsorption experiments were conducted at varied operational conditions. The adsorption kinetic was well described by pseudo-second-order kinetic model, whereas adsorption isotherm results elucidated that Freundlich model provided the best fit for the equilibrium data. Results indicated that the adsorption equilibrium can be achieved within 12 min, with the adsorption capacity of 237.6 mg g−1 even if 30 wt% PGS was incorporated as nanofiller. The as-prepared MSAF product not only had high removal efficiency for ammonium in a wide pH range of 4.0–8.0 but also exhibited an excellent slow-release property. The nitrogen-laden carrier material with a nitrogen content of 13.2% exhibits preferable slow-release properties with nitrogen being 60% released in soil for 10 days. Moreover, due to the composite material had preferable water-absorbing and water-retention capacity, thus it can improve soil moisture content and reduce soil moisture evaporation rate. The results suggested that the product with good water-holding and slow-release capacities could conserve soil moisture and was economical and eco-friendly for wide applications in modern agriculture and horticulture.

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