A review of the pyrolysis process of used tyre as a method of producing an alternative energy source is presented in this paper. The study reports the characteristics of used tyre materials and methods of recycling, types and principles of pyrolysis, the pyrolysis products and their composition, effects of process parameters, and kinetic models applied to pyrolysis. From publications, the proximate analysis of tyre rubber shows that it is composed of about 28.6 wt.% fixed carbon, 62 wt.% volatile material, 8.5 wt.% ash, and 0.9 wt.% moisture. Elemental analysis reveals that tyre rubber has an estimated value of 82 wt.% of C, 8 wt.% of H, 0.4 wt.% of N, 1.3 wt.% of S, 2.4 wt.% of O, and 5.9 wt.% of ash. Thermogravimetry analysis confirms that the pyrolysis of used tyre at atmospheric pressure commences at 250°C and completes at 550°C. The three primary products obtained from used tyre pyrolysis are solid residue (around 36 wt.%), liquid fraction or biocrude (around 55 wt.%), and gas fraction (around 9 wt.%). Although there is variation in the value of kinetic parameters obtained by different authors from the kinetic modeling of used tyre, the process is generally accepted as a first order reaction based on Arrhenius theory.

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This study investigated the optimisation of fermentation conditions during citric acid production via solid state fermentation (SSF) of pineapple peels using Aspergillus niger. A three-variable, three-level Box-Behnken design (BBD) comprising 17 experimental runs was used to develop a statistical model for the fermentation process while response surface methodology (RSM) was used for the optimisation of fermentation conditions. Increasing the fermentation temperature and the moisture content of the solid substrate enhanced the production of citric acid. Increasing the broth pH did not favour citric acid production as higher citric acid concentrations were recorded at low pH values. These results showed that citric acid production was influenced by these variables (i.e. temperature, moisture content and pH). The optimal fermentation conditions were determined as follows: fermentation temperature, 35 o C; broth pH, 2 and initial moisture content, 84.56%. The maximum concentration of citric acid produced under these conditions was 72.41 g/l. These results imply that the metabolic activity of the fermenting organismn (Aspergillus niger) used in this study was maximum at these optimised conditions. Validation of the statistical model indicated no difference between predicted and observed values as seen in the high correlation between model predicted results and experimental results.

Parts of the Nigerian Niger Delta which also accommodates huge number of oil facilities has swamps in some parts with non-turbulent water bodies. These water bodies are negatively impacted from oil pollution but lack the capacities to self-clean like high flowing waters. The calm nature of these swamps result in higher than normal retention, partitioning and diffusion of hydrocarbon components. This study investigated aliphatic and aromatic hydrocarbon concentrations at different depths for a period of ten months by simulating an oil spill site (8m by 5m and 1.5m deep) typical of a non-turbulent mangrove swamp with suspended sediments and vegetation polluted with 60 litres of crude oil. Impacted water samples were collected at depths of 0.25m, 0.5m, 0.75m and 1.0m. They were filtered and the petroleum aliphatic and aromatic contents analyzed using a GC-FID. The results obtained showed that petroleum hydrocarbons can dissolve and diffuse to different depths at concentrations above safe limits, thus posing great danger to aquatic life and its entire value chain.

The removal efficiency of activated carbons prepared from rice husk and coconut shell in the adsorption of methylene blue (azo dye) from the synthetic industrial wastewater was investigated in a batch system. Rice husk and coconut shell were both processed into activated carbon by carbonizing at 600 o C and activated with 3.0 M H3PO4 at 80 o C for 3h. Synthetic solutions of methylene blue were prepared and the adsorption process was carried out by varying initial, methylene blue concentration, adsorbent dosage, and contact. The results showed that higher values of adsorbent dosage and contact time favored the adsorption of methylene blue from the simulated waste water. Activated carbon from coconut shell proved a better adsorbent compared to the activated carbon obtained from rice husk as coconut shell has the highest percentage removal for methylene blue.

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The adsorption and desorption kinetics of naphthalene, anthracene, and pyrene in a soil slurry reactor at ambient conditions have been investigated to ascertain the mechanisms controlling the retention and release rates of these compounds in the soil matrix. A stirred-flow method was employed to perform the experiments. The extent of partitioning for the polycyclic aromatic hydrocarbons (PAHs) tested was found to be dependent on their solubility and diffusivity in the aqueous phase. Apparent adsorption and desorption rate coefficients were determined using the Langmuir and Freundlich isotherm models. Equilibrium adsorption and desorption at the external surface and in the internal pore of the soil particle obeyed the Freundlich isotherm equation. The pseudo-equilibrium condition established at the minimum contact time suggests that equilibrium adsorption attained for the contaminant PAHs was not instantaneous but rather time dependent.