## 1 Introduction  
Phosphorus (P) is a vital macronutrient that promotes the growth and development of living organisms. The rapidly burgeoning human population has led to a rising demand for high agricultural and industrial productivity, which, inevitably, has led to an exponential increase in the consumption of fertilizer and detergent. Since P is present in several minerals and rocks, it is a fundamentally non-renewable resource. Unfortunately, the most accessible high-grade P in rocks and minerals is being exhausted. Over the next 50-100 years, P in rock reserves worldwide are expected to become depleted [1]. On the other hand, pernicious eutrophication and algae bloom of receiving waters, such as rivers, reservoirs, lakes, and coastal waters have become worldwide environmental problems, characterized by the rapid growth of cyanobacteria and algae that consume a considerable amount of dissolved oxygen and cause the subsequent death of aquatic life [2]. The consequences of these processes are the disruption of the ecological balance in water ecosystems and the deterioration of freshwater quality [3]. The excessive discharge of P into aquatic ecosystems results in these problems. Eutrophication leads to fish death and habitat degradation with the loss of plant and animal species [4]. Rapid decomposition of dense algae scum can give rise to fuel odors and promote the growth of blue-green algae, which produce extensive toxic blooms [5; 6]. Eutrophication can also promote parasitic infections and amphibian diseases [7]. Recent reports suggest that phosphorus reduction effectively controls eutrophication [8; 9]. Stringent legislation to curb P emissions has been established in many countries. In China, the discharge limit of P recommended for wastewater treatment plants is 0.5 mg/L for class 1 (as total P) [10]. Thus, there is an urgent demand for ways to recover P, as well as to decrease P-rich effluent to below threshold values to protect water bodies from eutrophication. Diverse techniques have been applied to remove P from effluent, including physical, chemical, and biological processes. Although chemical methods such as precipitation [11] and coagulation [12] are relatively efficient for P removal, the disposal of accumulated sludge and secondary pollution caused by high chemical consumption are the main disadvantages of chemical methods [3]. As an alternative, biological treatment is considered feasible for P removal [13]. As they rely on phosphorus-accumulating bacteria, such systems are quite sensitive to water properties such as temperature and pH. Therefore, these systems are less stable and reliable, complex, and occupy a large area, which restricts the development of biological methods. Furthermore, electrodialysis does not satisfy the discharge requirements for effluent quality and requires post-treatment [14]. Currently, the sorption approach has shown great potential for P removal from contaminated water. Its advantages include low power consumption, low operating cost, convenient operation [15]. Therefore, the key issue is to find efficient adsorbents. Numerous natural and synthetic adsorbents, such as dolomite [16], clay minerals [17], orange waste [18], graphene [19], metal oxides [20], and activated alumina [21] have been introduced as alternatives for lowering P levels in aqueous solution. It has been reported that P has a relatively strong affinity for mineral surfaces [21]. Among these adsorbents, metal oxides (including hydroxides and oxyhydroxides), such as iron (hydr) oxides, are gaining popularity, owing to their high selectivity toward P. P can strongly adsorb onto the surface of metal oxides, especially iron and aluminum oxides rich in soils and sediments, including hematite (\(\alpha\)-Fe\({}_{2}\)O\({}_{3}\)), magnetite (Fe\({}_{3}\)O\({}_{4}\)), maghemite (\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)), goethite (\(\alpha\)-FeOOH), gibbsite(\(\alpha\)-Al(OH)\({}_{3}\)), boehmite (\(\gamma\)-AlOOH), and feroxyhite (\(\delta\)-FeOOH) [22; 23; 24].