## 4 Future Perspectives
\begin{table}
\begin{tabular}{c c} \hline \hline
**Application** & **Reference** \\ \hline Lactose free milk & [160] \\ \hline Harvesting certain microalgae & [161] \\ \hline Supplement in animal feed & [162] \\ \hline Stabilization of lateritic soils for construction materials & [163] \\ \hline Metal matrix composites and friction materials & [164] \\ \hline Thermoplastic composite fillers & [25] \\ \hline Bone mineralization & [25, 165] \\ \hline High temperature carbon monoxide capture & [153, 166, 167, 168, 169] \\ \hline Adsorption based-removal of insecticides in beverage samples & [166] \\ \hline Solvent assisted solid phase extraction of PAHs & [170] \\ \hline Adsorptive removal of non-radioactive strontium from aqueous solutions & [171] \\ \hline Removal of divalent metal ions e.g., cadmium, lead & [37, 150] \\ \hline Adsorptive removal of organics (neutral red, bromocresol green and tetracycline HCl) & [172] \\ \hline Application to solar thermochemical energy storage & [173] \\ \hline Sorption of dyes & [174] \\ \hline Separation and magnetic extraction of superparamagnetic composite materials & [175] \\ \hline Dichlorination and liquefaction of mixed plastics containing PVC & [176] \\ \hline Dehalogenation: removal of Br\({}^{-}\) and Cl\({}^{-}\) & [176] \\ \hline HCl gas capture via adsorption & [177] \\ \hline Desulphurization of dibenzothiophene & [178] \\ \hline Recovery of F\({}^{-}\) from wastewater & [9] \\ \hline \hline \end{tabular}
\end{table} 
Table 10: _Cont._fillers. In addition, it was reported that natural rubber mixed with ES filler has similar properties as a flame retardant and curing agent, with those made from conventional calcium carbonate [183]. As well, natural rubber with ES filler had similar tensile strength in comparison to those mixed with mineral CaCO\({}_{3}\)[153]. ES particles were used as low-cost catalysts in chemical transformations and organic synthesis, along with the production of biodiesel by the transesterification of vegetable oils with methanol [184; 185; 186]. Although ES was applied to agricultural soil to increase soil pH, ES was also used as a stabilizing agent for clay-related components, where it is used to stabilize lateritic soils for construction materials [163]. In turn, ES addition can also improve soil quality by reducing the plastic indices of soil samples. A key sustainability goal is to develop unique types of ESP-based composites for potential replacement of abiogenic CaCO\({}_{3}\) (derived from limestone) with biogenic systems derived from ES for various products, especially where calcite mineral is required. Biogenic alternatives will serve to address waste disposal by valorization of eggshells and offset the cost of mining, production, and preservation of the physical environment due to potential disruptive activities relevant to mining operations. An area of interest in the scientific literature that is under-reported relates to green disposal techniques for'spent' ESP adsorbents. Much of the research reported relates to laboratory scale studies, where the use of ESP biocomposite adsorbents at the pilot scale is recommended as an area of future work. Pilot scale studies apply to real industrial wastewater treatment in a dynamic process versus simulated \"laboratory\" wastewater, along with techno-economic analysis of ESP. Since various reports indicate that CES outperformed ESP, the diversion of eggshell waste from landfills can potentially reduce harmful leachate from landfills to other material platforms for other value-added products (e.g., preparation of calcium phosphate bioceramics such as hydroxyapatite) [187]. Based on the results presented for various types of ESP composite adsorbents, it can be concluded that the adsorption properties toward a range of pollutants (dyes, organics, and ionic species) reveal variable levels of removal efficiency.