In vitro assessment of cytotoxicity of spent fluid catalytic cracking refinery catalysts on cell lines and identification of critical toxic metals.

The Purpose of the present study was to quantify the responses of ten cell lines (HeLa, HepG2, HEK293, MDA-MB-231, A498, A549, A357, 3 T3, BALB-C3 T3, and NIH-3 T3) to spent fluid catalytic cracking catalysts (SFCCCs) from different petroleum refineries, and relate these responses to metal concentrations of SFCCC leachates (SFCCCLs). Cytotoxicity of SFCCCs were significantly different depending on cell lines. A357 and 3 T3 cell were the most sensitive, and A498 and HeLa cells were the least sensitive. HEK293 cells showed the least fluctuation in toxic response to different SFCCCLs among all cells. Cytotoxic IC50 values of SFCCCs to 7 kinds of cells were the most correlated with vanadium (V) concentration in SFCCCLs. V is the most critical toxic factor of SFCCC. Glutathione synthesis was induced in HepG2 cells exposed to higher concentrations of SFCCCLs. SFCCCLs with low concentration of V can induce the decrease of GSH/GSSG ratio in HepG2 cells, suggesting that high concentration of V inhibits the detoxification of glutathione.

Bioleaching of metals from spent fluid catalytic cracking catalyst using adapted Acidithiobacillus caldus.

In this study, an adapted bioleaching strain of Acidithiobacillus caldus UVS10 was successfully developed. Batch tests and tests in bioreactor were conducted to evaluate the metals bioleaching performance of A. caldus UVS10 to spent FCC catalyst (SFCCC). Results of batch experiments showed the bioleaching efficiency of Ni, V, La, and Ce in SFCCC reached 19.40%, 22.06%, 53.75%, and 59.56%, respectively. High SFCCC pulp density inhibited the leaching of metals. Sb leaching was inhibited in acidic environment caused by A. caldus UVS10. Contents of Ni, V, La, and Ce in extracellular polymeric substances (EPS) were significantly higher than those intracellular. Accumulation of metal in EPS and cytosol increased with the increase of SFCCC pulp density. V was less intercepted by EPS than Ni, La, and Ce, because of lower toxicity. Experimental results in bioreactor showed that Ni, V, La, and Ce could be effectively leached by A. caldus UVS10 under 10% pulp density. The aeration and stirring operating environment in bioreactor improved the leaching efficiency of metals in SFCCC. After bioleached in bioreactor, the available fraction content of four metals in SFCCC decreased significantly. Ecological risk analysis demonstrated the environmental risks of bioleached SFCCC were significantly lower than raw SFCCC. Different reaction kinetic models were used to represent metals leaching behavior under bioleaching of A. caldus UVS10, leaching of La and Ce showed good agreement with the product layer diffusion model, while Ni and V leaching kinetics fit well with the surface chemical reaction models.

Assessment of ecotoxicity of spent fluid catalytic cracking (FCC) refinery catalysts on Raphidocelis subcapitata and predictive models for toxicity.

The 17 spent fluid catalytic cracking refinery catalysts (SFCCCs) from different petroleum refineries were collected and the leachates of SFCCCs were prepared. The ecotoxicity of SFCCC leachates to Raphidocelis subcapitata was assayed. The results showed that the toxicity of the 17 SFCCCs differ greatly. Ji SFCCC was the most toxic to R. subcapitata with a 96 h EC50 value of 1.38%, while Ha SFCCC was the least toxic, with the EC50 value was >100%. The relationships between the toxicity of SFCCCs and the metal concentrations in leachates were analyzed. The concentration of Ni (p = 0.001), La (p = 0.001), Mn (p = 0.014), Ce (p = 0.017), Co (p = 0.018), and Ca (p = 0.031) in leachates showed significant correlation with EC50 values. The predictive model for the ecotoxicity of SFCCCs were established with the concentrations of Ni and La in leachates as: ln(EC50) = 0.817 + exp(1.356 - 1.736 × CNi - 0.262 × CLa) (R2 = 0.926). The main toxic ingredients of SFCCC to microalgae were identified for the first time in this work. The results and predictive model of this study are significance for toxicity determination and management of SFCCCs.

[Spatial Distribution, Source and Ecological Risk Assessment of Heavy Metals in the Coastal Sediments of Northern Dongying City].

Concentrations of seven heavy metals in the coastal sediments of the northern Dongying City were measured. The spatial distribution and sources of heavy metals were discussed and the ecological risk was assessed using sediment quality guidelines (SQGs) and the potential ecological risk index (PERI). The concentration ranges of Hg, As, Pb, Cd, Cr, Cu, and Zn were calculated as 0.005-0.092, 3.44-10.41, 6.59-19.00, 0.50-1.10, 32.42-60.25, 1.72-23.78, and 31.13-69.96 mg·kg-1, respectively. Higher metal concentrations were observed at site S10, which was close to the mouth of Tiaohe River and contained plenty of organic matter, silt, and clay. Principal component analysis (PCA) indicated that As and Pb in the sediments were derived from natural weathering processes, while other metals were mainly attributed to anthropogenic sources, i.e., land-sourced pollutants transported by runoff. Concentrations of As, Cd, Cr, and Cu at some sampling sites exceeded the threshold effect level (TEL) stated in the SQGs implying occasional harmful effects on biological life. PERI showed that the sediments in this area generally had a medium risk, except sites S10, S3, and S9 posing a considerable risk, and that Cd and Hg were the major contributors to the ecological risk. It is necessary to take effective measures to control heavy metal fluxes from rivers around this area and to reduce the risk.

[Vertical Variation of Phosphorus Forms in Lake Dianchi and Contribution to Release].

Columnar sediment samples were collected from the Waihai of Lake Dianchi in northern, central and southern sediment, combined with the data of phosphorus in the overlying water and sediment organic matter, the effects of organic matter and particle size on sediment release were studied, and the influence of different forms of phosphorus release from sediments and their contributions were discussed. The results showed:Sediment pore water ρ(DTP) and ρ(SRP) was negatively correlated with contents of OM, clay (<4.00 µm) and silt (4.00-63.00 µm), but it showed a significant positive correlation with sand (>63.00 µm) content. Theincrease in organic matter content of the sediments significantly reduced the gap water phosphorus mass concentration, and increasing clay and silt contents reduced the gap water phosphorus mass concentration, inhibiting the release of phosphorus in sediments. Potentially mobile phosphorus of the Lake Dianchi sediment was significantly positively correlated with the clay and silt contents, and was significantly negatively correlated with the sand content. It was indicated that clay and silt may enhance the phosphorus movement ability of the sediment, and the sand may enhance the retention of phosphorus in the sediment. In a short time scale, phosphorus of sediment was released mainly in northern Waihai, staying mainly in central and southern; in a longer time scale, phosphorus of sediment was released mainly in northern and central Waihai, staying mainly in southern. Control of phosphorus release from sediments in Lake Dianchi should take into account the effects of different forms of phosphorus, organic matter and particle size, and take corresponding measures to control the release of phosphorus in sediments of northern Dianchi mainly.