USE OF IRON-IMPREGNATED GRANULAR ACTIVATED CARBON FOR CO-ADSORPTIVE REMOVAL OF PHENOL AND CYANIDE: INSIGHT INTO EQUILIBRIUM AND KINETICS

Degradation pathway and microbial mechanism of high-concentration thiocyanate in gold mine tailings wastewater

As one of the inorganic pollutants with the highest concentration in the waste water of gold tailings using biohydrometallurgy, thiocyanate (SCN-) was effectively degraded in this research adopting a two-stage activated sludge biological treatment, and the corresponding degradation pathway and microbial community characteristics in this process were also studied. The results showed that SCN- at 1818.00 mg L-1 in the influent decreased to 0.68 mg L-1 after flowing through the two-stage activated sludge units. Raman spectroscopy was used to study the changes of relevant functional groups, finding that SCN- was degraded in the COS pathway. Based on 16S rRNA high-throughput sequencing technology, the microbial diversity in this system was analyzed, and the results indicated that Thiobacillus played a major role in degrading SCN-, of which the abundance in these two activated sludge units was 32.05% and 20.37%, respectively. The results further revealed the biological removal mechanism of SCN- in gold mine tailings wastewater.

Single and binary adsorption of heavy metal ions from aqueous solutions using sugarcane cellulose-based adsorbent

A high efficient and eco-friendly sugarcane cellulose-based adsorbent was prepared in an attempt to remove Pb²⁺, Cu²⁺ and Zn²⁺ from aqueous solutions. The effects of initial concentration of heavy metal ions and temperature on the adsorption capacity of the bioadsorbent were investigated. The adsorption isotherms showed that the adsorption of Pb²⁺, Cu²⁺ and Zn²⁺ followed the Langmuir model and the maximum adsorptions were as high as 558.9, 446.2 and 363.3mg·g^-1, respectively, in single component system. The binary component system was better described with the competitive Langmuir isotherm model. The three dimensional sorption surface of binary component system demonstrated that the presence of Pb²⁺ decreased the sorption of Cu²⁺, but the adsorption amount of other metal ions was not affected. The result from SEM-EDAX revealed that the adsorption of metal ions on bioadsorbent was mainly driven by coordination, ion exchange and electrostatic association.

Control of occupational exposure to phenol in industrial wastewater treatment plant of a petroleum refinery in Alexandria, Egypt: An intervention application case study

Phenol exposure is one of the hazards in the industrial wastewater treatment basin of any refinery. It additively interacts with hydrogen sulfide emitted from the wastewater basin. Consequently, its concentration should be greatly lower than its threshold limit value. The present study aimed at controlling occupational exposure to phenol in the work environment of wastewater treatment plant in a refinery by reducing phenolic compounds in the industrial wastewater basin. This study was conducted on both laboratory and refinery scales. The first was completed by dividing each wastewater sample from the outlets of different refinery units into three portions; the first was analyzed for phenolic compounds. The second and third were for laboratory scale charcoal and bacterial treatments. The two methods were compared regarding their simplicities, design, and removal efficiencies. Accordingly, bacterial treatment by continuous flow of sewage water containing Pseudomonas Aeruginosa was used for refinery scale treatment. Laboratory scale treatment of phenolic compounds revealed higher removal efficiency of charcoal [100.0(0.0) %] than of bacteria [99.9(0.013) %]. The refinery scale bacterial treatment was [99.8(0.013) %] efficient. Consequently, level of phenol in the work environment after refinery-scale treatment [0.069(0.802) mg/m(3)] was much lower than that before [5.700(26.050) mg/m(3)], with removal efficiency of [99.125(2.335) %]. From the present study, we can conclude that bacterial treatment of phenolic compounds in industrial wastewater of the wastewater treatment plant using continuous flow of sewage water containing Pseudomonas Aeruginosa reduces the workers' exposure to phenol.