In order to improve the efficiency of bioleaching heavy metal from the contaminated soil using Penicillium chrysogenum(P.chrysogenum),experiment was conducted to evaluate the influence of heavy metal stress on P.chrysogenum during bioleaching.The morphology and physiology of P.chrysogenum were observed.Assuming that the heavy metals are all leached out from the experiment soil,heavy metals are added into the agar medium by simulating the heavy metal content in the soil.It is concluded that the survivable heavy metal contaminated soil mass range for P.chrysogenum is 2.5-5.0 g.As for biomass determination,the contaminated soil is added into the liquid medium directly.The soil mass that P.chrysogenum can be survivable is in the range of 2.5-8.75 g.In this mass range,the biomass of P.chrysogenum is bigger than that of the control sample.10 g soil mass is the threshold of the growth of P.chrysogenum.102.2 mg/L gluconic acid,156.4 mg/L oxalic acid,191.6 mg/L pyruvic acid,0.02 mg/L citric acid,0.03 mg/L malic acid and 70.6 mg/L succinic acid are determined after 15 d bioleaching.The mycelium is broken into fragments,and heavy metals are adsorbed on the cell wall or transported into the cytoplasm during bioleaching.The GOD activity declines from 1.08 U/mL to 0.2 U/mL under 400 mg/L of multi-metal stress.The influence of Pb on GOD activity is bigger than that of Cr and Cd,and the GOD activity is not influenced apparently by Mn,Zn and Cu.
Bench-scale soil column experiments were carried out to evaluate the effectiveness of Cr(VI) bioremediation process in soils by using indigenous bacteria with the addition of bacteria nutrient media. Effects of particle size, spray intensity, initial Cr(VI) concentration, circulation mode and soil depth on Cr(VI) remediation were studied. Results show that soils after 6 d remediation with spray intensity controlled in the range of 29.6-59.2 mL/min could well fulfill the requirement of concrete aggregate and roadbed material usage, for the leaching toxicity concentration of the Cr(VI) in treated soils under the chosen condition is far less than 5 mg/L. The leaching toxicity and fractions of both hexavalent chromium and trivalent chromium from remediated soils were determined and compared with that of untreated soil. The results show that water soluble Cr(VI) declines from 1520.54 mg/kg to 0.68 mg/kg, exchangeable Cr(VI) decreases from 34.83 mg/kg to 0.01 mg/kg and carbonates-bonded Cr(VI) falls from 13.55 mg/kg to 0.68 mg/kg. Meanwhile, a corresponding increase in carbonate-bonded Cr(III), Fe and Mn oxides-bonded Cr(III) and organic matter-bonded Cr(III) are found. It reveals that indigenous bacteria can leach out water soluble Cr(VI), exchangeable Cr(VI) and carbonates-bonded Cr(VI) from contaminated soil followed by converting into carbonate-bonded Cr(III), Fe and Mn oxides-bonded Cr(III), organic matter-bonded Cr(III) and residual Cr(III).
The electrochemical degradation of reed pulp black liquor containing lignin pretreated by acidification method was investigated using a three-dimensional electrode reactor. Using activated carbon as particle electrode, the effects of p H value, reaction temperature, electrolysis time and current on residual concentration of total organic carbon(TOC) were discussed in detail. The optimal conditions were obtained: pH 2.5, influent flow rate of 200 mL/min, 25 °C, 300 mA and 2h of electrolysis time, and the removal efficiency of TOC maintains at 35.57 %. The results of the electrochemical method indicate that ·OH radicals are produced in activated carbon anode in the electrolysis process and then adsorbed on the activated carbon surface. Microcell consists of ·OH radicals and the absorbed lignin. With the microcell reaction, the lignin is degraded, while the anodic polarized curve illustrates that the lignin is obviously oxidized in the anode. The contributions of direct and indirect electrolyses to the TOC removal ratio are about 50%, respectively.
Bioleaching is an environment-friendly and economical technique to remove heavy metals from contaminated soil.The objective of this work is to find out an indigenous strain to remedy soil contaminated by Zn,Pb,Cu and Cd.A strain which was selected from the soil of a local smelting industry was found to be able to produce many organic acids and degrade pH value of the liquid medium.The fungus strain is identified as Penicillium Chrysogenum (P.Chrysogenum) by sequencing 18srDNA and ITS.Bioleaching condition using P.Chrysogenum is optimized.Glucose is the best carbon source for P.Chrysogenum and inorganic nitrogen is better than organic nitrogen.In addition,neutral solution and room temperature are fit for P.Chrysogenum to bioleach.In the one-step bioleaching,the bioleaching ratios are 39.95% for Zn,9.4% for Pb,34.89% for Cu and 49.59% for Cd,which are 53.89% for Zn,14.44% for Pb,55.53% for Cu and 62.81% for Cd in the two-step bioleaching.The efficiency of two-step bioleaching is better than the one-step bioleaching.P.Chrysogenum is effective in removing heavy metals from the contaminated soil.
A batch experiment was conducted to investigate the adsorption of trivalent chromium (Cr(Ⅲ)) from aqueous solutions by sugarcane pulp residue (SPR) and biochar. The results show that Cr(Ⅲ) adsorption by SPR and biochar is highly pH-dependent and Cr(Ⅲ) adsorption amount increases with the increase of pH. The adsorption kinetics of Cr(Ⅲ) fits well with the pseudo-second-order model. The maximum Cr(Ⅲ) adsorption capacities of 15.85 mg/g and 3.43 mg/g for biochar and SPR were calculated by Langmuir model. This indicates that biochar has a larger ability for Cr(Ⅲ) adsorption than SPR. The free energy change value (ΔG) reveals a spontaneous sorption process of Cr(Ⅲ) onto SPR and non-spontaneous sorption process onto biochar. The entropy change (ΔS) and enthalpy change (ΔH) are found to be 66.27 J/(mol·K) and 17.13 kJ/mol for SPR and 91.59 J/(mol·K) and 30.875 kJ/mol for biochar which further reflect an affinity of Cr(Ⅲ) onto SPR and biochar. It is suggested that biochar has potential to be an efficient adsorbent in the removal of Cr(Ⅲ) from industrial wastewater.
Soil contaminated with typical heavy metals (Pb,Cd,Cu,and Zn) was remedied by using the polymeric aluminum salt coagulants including polyaluminum chloride (PAC) and polyaluminum sulfate (PAS).The remediation efficiencies are influenced by reaction time,water amount,and dosage of remediation agent.The optimal remediation conditions are as follows:6 h of reaction time,1 kg/kg of water addition amount,and 0.25 kg/kg of remediation agent dosage.After PAC addition,the remediation efficiencies of diethylenetriamine-pentaacetic acid (DTPA)-extractable Pb,Cd,Cu,and Zn reach 88.3%,85.1%,85.4%,and 73.7%,respectively;and those for PAS are 89.7%,88.7%,83.5%,and 72.6%,respectively.The main remediation mechanism of the polymeric aluminum salt may contribute to the ionization and hydrolysis of PAC and PAS.H + released from ionization of polymeric aluminum salt can cause the leaching of heavy metals,while the multinuclear complex produced from hydrolysis may result in the immobilization of heavy metals.For PAC,the immobilization of heavy metals is the main remediation process.For PAS,both leaching and immobilization are involved in the remediation process of heavy metals.
