Incorporation of pyridinic and graphitic N to Ni@CNTs: As a competent electrocatalyst for hydrogen evolution reaction

Cheap production of hydrogen (H₂) from eco-friendly routes is preeminent for solving future energy challenges. This study explores the hydrogen evolution reaction (HER) activity of nickel (Ni) nanoparticles and nitrogen doped carbon nanotubes (NiNCNTs), which are fabricated by a cheap and one-step pyrolysis method. The most active catalyst synthesized at 800°C exhibits an overpotential of 0.244 V to reach a current density of 10 mA cm⁻², Tafel slope of 93.3 mV dec⁻¹ and a satisfactory 10 hours stability. Low resistance and large ECSA value of the sample also favor the competent response for HER in alkaline media. The robust HER activity of the catalyst is as a result of the nickel nanoparticles which are the active spots of reaction; while the presence of well-developed nitrogen containing carbon nanotubes with large content of pyridinic and graphitic nitrogen may provide high-electron density and feasible routes for its transportation to deliver an outstanding HER performance.     

Remediation of oil spill polluted water from Niger Delta Nigeria by sorption onto ammonium sulfate modified Dialium guineense seed husk

The abstraction of crude oil molecules from aqueous solution (produced water) and from real petroleum polluted water (collected from River State, Nigeria) by Dialium guineense Seed Husk (DGSH) and its ammonium sulfate functionalized form (AS-DGSH) was studied using a batch technique. The sorbents were characterized using Fourier transform infrared (FTIR), BET surface area analysis and the Scanning electron microscopy (SEM). Crude oil characterization revealed a light crude oil based on the API gravity of 35.6⁰. The Langmuir and Freundlich models gave good fits for crude oil sorption on DGSH and AS-DGSH respectively. The sorbents were found to remove over 50% of crude oil from the real polluted water at the natural pH of 6.1 and showed increase in removal with increase in sorbent dose. The potential of DGSH and its ammonium sulfate modified derivative as effective low cost sorbents for oil spill treatment was established.     

Evaluation of Air Oven Moisture Content Determination Procedures for Pearl Millet (Pennisetum glaucum L.)

This study evaluated moisture content determination procedures for pearl millet using seven different air oven methods. The moisture content of the pearl millet samples varied from 11–41% (wet basis). The procedures included 130°C for 1 h; 130°C for 2 h; 105°C for 5 h; 105°C for 48 h; 105°C for 72 h; 130°C for 16 h; and 130°C for 20 h. Analysis of variance revealed that at high moisture content levels above 27% (wet basis), and the mean values of the moisture content determined were not significantly different (p > 0.05). Error analysis carried out showed that the moisture content determination methods were adequate to completely remove the moisture in pearl millet with moisture less than 35% (wet basis). Regression models were developed to predict the base moisture determination method (105°C for 72 h) as a function of other procedures.     

Equilibrium isotherms modeling of crude oil sorption from aqua mixture onto Codiaeum variegatum stem powder

Codiaeum variegatum stem powder (CVSP) was used as a low cost, readily available and biodegradable sorbent for decontamination of crude oil from aqueous solution. CVSP was characterized by the FTIR, SEM and BET techniques. The physical characterization of the crude oil showed light crude. Equilibrium isotherm of crude oil uptake was analyzed by the Langmuir, Feundlich, Tempkin, Flory-Huggins and Scatchard models. The Langmuir isotherm gave best fit with regression of 0.995 indicating a homogenous CVSP surface involving monolayer sorption of crude oil, supported by the Scatchard model analysis. The maximum monolayer uptake capacity of CVSP for crude oil was established and compared to other reported sorbents.     

Slope stability analysis of mine waste dumps at a mine site in Southeastern Nigeria

This paper presents results on the stability of slopes of the mine tailing dumps at Enyigba, Southeastern Nigeria. The geotechnical parameters of the slopes were investigated, and stability analysis was carried out with GeoStudio® 2012 developed by Geoslope International Limited. The slope materials were composed of gravel (1.42–30.13%), sand (15.94–33.34%), silt (9.75–26.87%) and clay (32.1–56.25%). The materials have LL, PL and PI ranging from 24 to 49%, 24 to 35% and 9 to 26% respectively, signifying low to medium plastic materials. These results agree with the soil low permeability (10⁻⁴ – 10⁻⁸ cm/s) recorded. The MDD and OMC of the material ranged from 1.86 to 2.22 g/cm³ and 13.45 to 17.05%, while cohesion and internal friction angle were recorded to be 13–34 kN/m² and 8–37° respectively; implying moderately durable materials capable of slip and shear failures. XRD confirmed the presence of swelling mineral (illite) in soil material, hinting at clay plasticity on absorption of moisture, which is one of the factors influencing all forms of mass wasting. The slopes’ computed factor of safety ranged from 0.8 to 1.33, suggesting critical to poor slope stability when exposed to landslide triggering agents. Hence, slope stabilization is required on the mine tailing dumps at Enyigba to prevent major landslide occurrence.

     

Physicochemical properties of five cocoyam (Colocasia esculenta and Xanthosoma sagittifolium) starches

Physicochemical properties of starches of five cocoyam cultivars were evaluated. CIE L^*, a^*, b^* colour parameters of corm and starches were measured. Amylose, pasting and functional properties of the starches were investigated using colourimetric, Rapid Visco-Analyser and standard methods respectively. Cocoyam starches were white in colour as shown by L^* (84.83–88.65), a^* (+0.01–+1.19), and b^* (+15.33–+16.54) values. Starch granule sizes varied significantly in length (6.47–13.63 μm) and width (5.36–8.45 μm), while amylose content ranged from 11.55% (NCe002) to 33.77% (NXs001). Peak (49.09–141.96 RVU), breakdown (49.09–141.96 RVU), final (189.79–327.42 RVU) viscosities, pasting temperature (84.53–88.75 °C) and time (4.55–4.97 min) varied significantly (p < 0.05) among cultivars. Also, water absorption capacity (21–36%), pH (4.8–5.3), gelling point (60.5–69.5 °C), foam capacity (4.46–18.28%), bulk density (0.14–1.15 g/mL) and swelling power (2.31–10.09) varied significantly (p < 0.05) among the cultivars. Average yield of the starches varied significantly from 10.03 (NCe001) to 18.61% (NXs001).     

Cobalt–Iron nanoparticles encapsulated in mesoporous carbon nanosheets: A one-pot synthesis of highly stable electrocatalysts for overall water splitting

Advancement of cost-effective, highly efficient and non-noble metal-based bifunctional electrocatalysts is considered an attractive approach to overcome the energy defect and environmental pollution challenges. Herein, this study presents a simple one-pot approach to synthesize cobalt-Iron nanoparticles encapsulated in mesoporous carbon nanosheets (Co₃Fe₇@CNSs) by the pyrolysis method. The Co₃Fe₇@CNSs-750/4h electrocatalyst exhibits a notable performance, low overpotential of 181 and 301 mV at a current density of 10 mA cm^?2 and small Tafel slope of 124.8 and 38.59 mV dec^?1, large active surface area 18.20 and 21.18 mF cm^?2, and low charge transfer resistance 4.92 and 9.42 Ω for hydrogen and oxygen evolution reactions, respectively, in 1.0 M KOH. Overall water splitting, with the set-up of two-electrode cells acquires the 10 mA cm^?2 of current density at 1.610 V in 1.0 M KOH. The combined structure of cobalt-iron nanoparticles encapsulated in carbon nanosheets; it could enhance the surface area and, provide more active sites that improve the overall catalytic activity. Not only this but also the synergistic effect due to different temperature treatments which significantly influenced the structural formation. However, the major involvement of this study is concerned with the production of economical non-noble metal-based electrocatalysts at an industrial scale for renewable energy to sustainability.