Enhanced adsorption and slow release of phosphate by dolomite–alginate composite beads as potential fertilizer

Abstract

The recovery and reuse of phosphorus (P) from wastewater treatment process is a critical and viable target for sustainable P utilization. This study explores a novel approach of integrating ultrafine mineral particles into hydrogel matrixes for enhancing the capacity of phosphate adsorption. Dolomite‐alginate (DA) hydrogel beads were prepared by integrating ball‐milled, ultrafine dolomite powders into calcium cross‐linked alginate hydrogel matrix. The adsorption isotherms followed a Langmuir–Freundlich adsorption model with higher specific adsorption capacity than those reported in literature. The kinetics of phosphate adsorption suggest that the adsorption is diffusion controlled. Investigation of adsorption capacity at different pH showed a maximum adsorption capacity in the pH range of 7–10. Lastly, we demonstrated that the DA beads are capable of slowly releasing most of the adsorbed phosphate, which is an important criterion for them to be an effective phosphorous fertilizer. This study, using DA composite hydrogel as an example, demonstrates a promising strategy of immobilizing ultrafine mineral adsorbents into biocompatible hydrogel matrix for effective recovery of phosphorous resource from wastewater. Practitioner points Integration of dolomite and alginate hydrogel beads is demonstrated using ball milling. Ball milling process increases the specific adsorption capacity of dolomite on phosphorus. Adsorption isotherms, kinetics, and pH effects of the dolomite–alginate beads are investigated. The dolomite–alginate beads can be used as slow‐release phosphorus fertilizer.

Dolomite surface modification with titanium and silicon precursors and its morphostructural and thermal characterisation

“…The SEM images obtained on raw dolomite (Figure 2, image A) show a high heterogeneity of particle sizes with variations from 1,512 µm to 14.08 µm. According to the literature, generally in raw dolomite, two types of aggregates can be observed: fine with dimensions between 1-4 µm and large with dimensions between 5-14 µm (Gruszecka-Kosowska et al, 2017;Huang et al, 2019). Moreover, the shape of the particles in dolomite is not well defined (irregular) and the aggregates have a smooth surface, without visible pores.…”

“…) in the presence of UV light (Nagase et al, 2014), filler in various polymeric matrices (polyester resins, alginates, polypropylene, etc.) (Saidi et al, 2019;Huang et al, 2019;Ozdemir et al, 2017). Although dolomite can be used in a wide range of applications, it is not exploited to its true potential, at the industrial level.…”

Hydrogel Alginate Seed Coating as an Innovative Method for Delivering Nutrients at the Early Stages of Plant Growth

“…Hence, it is utilized in many industries, including medical, pharmaceutical, food, packaging, etc. Agricultural applications of alginate are also known, mainly as a carrier of fertilizer nutrients [ 7 , 8 ] or as a component of slow-release coatings [ 9 ]. Even though the use of this polysaccharide in seed applications is not fully explored, seeds are known to have been encapsulated in growth regulators in an alginate coating [ 10 ], bacteria, i.e., Pseudomonas aeruginosa LY-11 [ 11 ], and mycoparasites Trichoderma asperellum [ 12 ].…”

Phosphorus recovery from wastewater using pyridine‐based ion‐exchange resins: Role of impregnated iron oxide nanoparticles and preloaded Lewis acid (Cu2+)

“…Sorption‐based processes have shown promise in removing P from wastewater. Materials used as a P sorbent include fly ash (Xu et al, 2012), tantalum hydroxide (Yu et al, 2012), iron‐based filter (Allred & Racharaks, 2014), dolomite‐alginate composite beads (Huang et al, 2019), palygorskite (Fangqun et al, 2011), activated alumina (Tan et al, 2019), plaster of paris and hydrogel beads containing alumina particles (Malicevic et al, 2020), calcium‐rich rocks (Lamont et al, 2019), and zirconium oxide (Lin et al, 2017). Most metal oxide particles lack the mechanical strength and abrasion resistance properties for prolonged operation in fixed‐bed units (Blaney et al, 2007).…”