Although the removal of arsenic(V) (As(V)) from solution can be improved by forming metal-bearing coatings on solid media, there has been no research to date examining the relationship between the coating and As(V) sorption performance. Manganese-coated bone char samples with varying concentrations of Mn were created to investigate the adsorption and desorption of As(V) using batch and column experiments. Breakthrough curves were obtained by fitting the Convection-Diffusion Equation (CDE), and retardation factors were used to quantify the effects of the Mn coatings on the retention of As(V). Uncoated bone char has a higher retention factor (44.7) than bone char with 0.465 mg/g of Mn (22.0), but bone char samples with between 5.02 mg/g and 14.5 mg/g Mn have significantly higher retention factors (56.8-246). The relationship between retardation factor (Y) and Mn concentration (X) is Y = 15.1 X + 19.8. Between 0.2% and 0.6% of the sorbed As is desorbed from the Mn-coated bone char at an initial pH value of 4, compared to 30% from the uncoated bone char. The ability of the Mn-coated bone char to neutralize solutions increases with increased amounts of Mn on the char. The results suggest that using Mn-coated bone char in Permeable Reactive Barriers would be an effective method for remediating As(V)-bearing solutions such as acid mine drainage.

No abstract

In addition to chemical factors, physical conditions also play a key role in the growth of microalgae. In this study, solid sediment in rivers was simulated by pure quartz sand with different particle sizes and the physical effects of disturbance rate, solid-liquid ratio and particle size on the growth of Chlorella vulgaris (C. vulgaris) were investigated through orthogonal analysis and response surface methodology (RSM) during co-cultivation of C. vulgaris and sediment. The result of ANOVA in orthogonal analysis showed that the effect ability of a single factor on biomass can be ranked as disturbance rate > particle size > solid-liquid ratio, 100 r/min disturbance rate and 30-40 M particle size are the most significant at the 0.05 level. Furthermore, the specific growth rate can reach 0.25/d and 0.27/d, respectively. With the growth of C. vulgaris, the pH of the solution reached a maximum of 10.7 in a week. The results from the RSM showed that strong interactions are reflected in the combinations of disturbance rate and solid-liquid ratio, and disturbance rate and particle size. Ramp desirability of the biomass indicates that the optimum levels of the three variables are 105 r/min disturbance rate, 0.117 g/mL solid-liquid ratio and 30-40 M particle size. In this case, the biomass can grow seven times in a week with 0.27/d specific growth rate and a pH value of 7-10.4. This study shows that the growth of C. vulgaris can be regulated by changing physical conditions simultaneously, and the optimization of physical conditions can be applied to biomass production, algae prediction and acid water treatment in rivers, lakes and reservoirs.

Iron phosphate (Fe–P) is a main phosphorus storage form, especially in phosphorus-polluted environments. The re-release of Fe–P is a problematic result during microalgal remediation. In this study, pre-incubated Chlorella vulgaris was cultured in a BG-11 culture medium with different amounts of Fe–P. The effects of Fe–P re-release on biomass, flocculation and removal of PO 4 3− were investigated. The results indicated that C. vulgaris can promote the dissolution and release of Fe–P when the pH is 7, and the amount of Fe–P (ΔQ) released in 200 ml water reaches 0.055–0.45 mg d −1 under a C. vulgaris concentration of 5.6 × 10 5 –8 × 10 5 cells ml −1 . The growth of C. vulgaris was inhibited because of the flocculation behaviour of Fe 3 + in the release stage, which is associated with a specific growth rate of 0.3–0.4 d −1 and a phosphorus removal rate below 30%. However, this process, in the long term, indicates a favourable transformation in which Fe–P becomes bioavailable under the action of C. vulgaris . Microalgae outbreaks may be triggered by persistent interactions between Fe–P and C. vulgaris . This study provides an important reference for the application of C. vulgaris in a Fe–P-rich environment.