Different dimensions abound to examine the famous Feldstein–Horioka Puzzle. However, after intense discussions of the subject matter for more than three decades, researchers are yet to reach consensus on the validity or otherwise of savings–investment relationship. In this paper, we revisited the Feldstein–Horioka saving‐investment puzzle, and augment their investment equation with factors that drive capital mobility, such as globalization, foreign direct investment, and urbanization using more recent annual frequency time series data over the periods 1981–2018 in the case of Nigeria. We employed unit root test with structural breaks/regime shifts inherent in time series data and Autoregressive Distributed Lag Bounds Testing for co‐integration of empirical estimates. Results show existence of a long‐run equilibrium relationship among variables. Domestic savings, real income, and foreign direct investment reveal positive impact, while globalization and urbanization exhibit negative impact on domestic investment both in the short and long run. We find strong capital mobility among savings–investment relationship, thus render potential policy suggestions that would drive domestic investment and bring about sustainable economic growth in the long run.

This study focused on the development of a novel Palladium (Pd)-Silver (Ag)-Carbon nanotubes adsorbent for the removal of Cu(II) and Ni(II) ions in industrial animal feed processing wastewater. Carbon nanotubes (CNTs) were produced via a catalytic chemical vapour deposition (CCVD) method and then purified by acid mixture of H2SO4 and HNO3. Pd-Ag-CNTs nanocomposites were produced through a combination of ultrasonic-assisted wet impregnation methods. Different analytical tools such as HRSEM, HRTEM, EDS, SAED, XRD and BET were used to characterize the prepared nanoadsorbent. The HRSEM analysis revealed homogeneous dispersion of Pd and Ag nanoparticles on the CNTs matrix. XRD pattern confirmed formation of graphitic face-centered cubic structure with or without metal matrix nanoparticles with an average crystallite sizes of 26.10 nm (Pd-Ag-CNTs) > 13.00 nm (Pure-CNTs). BET analysis showed that simultaneous addition of Pd and Ag nanoparticles onto CNTs contributed to enhanced surface area of (392.5 m2/g) compared to Pure-CNTs (227.63 m2/g). The effect of contact time, adsorbent dosage, and temperature on the nanoadsorbent efficacy with respect to Cu(II) and Ni(II) ions removal were investigated via batch adsorption mode. The optimum condition for the maximum removal of Ni(II) ions (99.84%) and Cu(II) ions (77.86%) by Pd-Ag-CNTs were contact time (90 min), adsorbent dosage (60 mg)and reaction temperature (60°C). The adsorption isotherm data best fitted Florry-Huggins model based on the χ2, SSE and regression co-efficient values of 0.9947 (Cu) and 0.7098 (Ni), while the kinetic data suited pseudo-second order. The thermodynamic study was found to be non-spontaneous and endothermic in nature. This study demonstrated for the first time that Pd-Ag-CNTs exhibited exceptional adsorptive and recyclability properties for the removal of Cu(II) and Ni(II) ions from industrial animal feed processing wastewater even after five cycles.