Evaluating the Ability of Bone Char/nTiO2 Composite and UV Radiation for Simultaneous Oxidation and Adsorption of Arsenite

The reuse of waste materials for water treatment purposes is an important approach for promoting the circular economy and achieving effective environmental remediation. This study examined the use of bone char/titanium dioxide nanoparticles (BC/nTiO2) composite and UV for As(III) and As(V) removal from water. The composite was produced via two ways: addition of nTiO2 to bone char during and after pyrolysis. In comparison to the uncoated bone char pyrolyzed at 900 °C (BC900), nTiO2 deposition onto bone char led to a decrease in the specific surface area and pore volume from 69 to 38 m2/g and 0.23 to 0.16 cm3/g, respectively. However, the pore size slightly increased from 14 to 17 nm upon the addition of nTiO2. The composite prepared during pyrolysis (BC/nTiO2)P had better As removal than that prepared after pyrolysis with the aid of ultrasound (BC/nTiO2)US (57.3% vs. 24.8%). The composite (BC/nTiO2)P had higher arsenate oxidation than (BC/nTiO2)US by about 3.5 times. Arsenite oxidation and consequent adsorption with UV power of 4, 8 and 12 W was examined and benchmarked against the composite with visible light and BC alone. The highest UV power was found to be the most effective treatment with adsorption capacity of 281 µg/g followed by BC alone (196 µg/g). This suggests that the effect of surface area and pore volume loss due to nTiO2 deposition can only be compensated by applying a high level of UV power.

Release and distribution changes of phosphorus in three alkaline sandy soils as a function of bone char applications

An incubation experiment was carried out to assess bone char application on the availability and distribution of phosphorus in agricultural alkaline sandy soils. Three alkaline agricultural sandy soils in Upper Egypt have been collected from Arab El-Awamer at Assiut governorate, West El-Minia at El-Minia governorate, and New Valley Governorate. 100 grams were taken from each soil under study and placed in a plastic jar. The bone char is applied at level 0.4 g jar-1 into these soils. This experiment was incubated at 23 ºC in the dark for periods of 7, 16, 35, 65, and 84 days and arranged in a completely randomized design with three replicates. The results revealed that bone char applications to the soils resulted in a significant positive increase in the availability of phosphorus affected by the soil type and incubation periods in Arab El-Awamer soil. The percentage of increase in available phosphorous after adding bone char compared to before incubation was as follows: Arab El-Awamer soil ˃New Valley soil ˃West El-Minia soil. The available phosphorous was negatively correlated with electrical conductivity (r=-0.288*), soluble calcium (r=-0.306*), and soluble sulfate (r=-0.413*). The concentrations of NH4Cl-Pi, NaHCO3-Pi, NaOH-Pi, HCl-Pi, residual-P fractions increased significantly in some soil types with applying bone char. The concentrations of available phosphorous in all soils under study were positively correlated with all phosphorus fractions. We conclude that bone char applications into P-poor soil are important to potentially enhance phosphorus availability. Bone char is considered a promising strategy in sustainable agriculture.