In this study, TiO2 nanocrystals, 1 mol% Ag-doped TiO2, and 1 mol% Ag and 0.6 mol% Zn co-doped TiO2 powders were synthesized by the sol–gel route. Their photocatalytic activities on methyl orange dye under visible irradiation were investigated. The powders were characterized by X-ray diffraction (XRD), UV–visible spectroscopy (UV–vis), Brunauer–Emmett–Teller (BET), and Fourier transform infrared spectroscopy (FTIR). The XRD results revealed the presence of a rutile phase with an average crystallite size of 9 and 11 nm. The UV–vis spectra showed a red-shift towards a longer wavelength with the corresponding decrease in band gap from 2.9 to 2.5 eV. The BET surface areas of the nanoparticles ranged from 4.7 to 11.8 m2 g−1 with an average pore size between 18.9 and 56.6 nm. The Ag-doped TiO2 has the largest surface area of 11.8 m2 g−1, whereas the Ag–Zn co-doped TiO2 was found to have the highest pore size and volume. The absorption bands at 750–500 cm−1 were attributed to the –O–Ti–O– bond in the TiO2 lattice. The photocatalytic efficiency was highest at an optimum pH of 4.1 for Ag–Zn co-doped TiO2. The results confirmed that Ag-doped and Ag–Zn co-doped TiO2 were more effective than pure TiO2. The kinetic data were fitted into a pseudo first-order equation using a Langmuir–Hinshelwood kinetic model.

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The use of water resources from hand-dug wells, boreholes and streams around cassava processing mills within Ilaro metropolis, Ogun State Nigeria for domestic and industrial activities had led to the assessments of water resources in the vicinities of Ekueme, Olorungbogo, Double Crown, Olalandu and Akewe cassava mills. Eleven water samples were collected and taken to the laboratories for physiochemical, heavy metals and microbial analyses. The values obtained were compared with the WHO standards for drinking water. The pH (4.68–7.41) revealed acidic water with relatively low temperatures (24.7–29.2 ℃). The EC (79.80–221.00 mS/cm) indicated very high level of dissolved ionic salts, TU (0.200–0.684 mg/L) revealed the presence of particulate matters, and TH (15.10–22.70 mg/L) showed moderate water hardness. The anions NO3−, PO43− and Cl− concentrations indicated contaminations ranging from 65.42–110.80, 7.210–8.310 and 195.25–427.00 mg/L, respectively. Cations Na+, Ca2+ and Mg2+ had relatively low concentrations ranging from 14.49–20.96, 4.30–11.29 and 10.50–11.50 mg/L, respectively. The concentrations of Fe, Ni, Cd and Pb were high and ranged from 3.87–5.10, 1.27–2.82, 0.07–2.69 and 0.03–0.96 mg/L, respectively. The microbial counts in for total bacteria, fungi, E. coli and total coliform were also high ranging from 1.0–93.0, 0.1–1.3, 0.1–9.2 and 0.1–9.3 (106 CFU/ml), respectively. All these parameters indicated statistically significant difference between their concentrations at p = 0.000 and between the physiochemical and microbial results at p = 0.006. The qualities of the water resources around the study areas had been highly compromised and are not suitable for domestic activities.