No abstract

In this work adsorption of heavy metal ions (Cu2+, Pb2+, Zn2+and Ni2+) from aqueous solution by chitosan was investigated in a batch reactor. Three commercially different viscosity chitosans were used as adsrobents. pH value, adsorption temperature, time and initial concentration had affected adsorption efficiency of metal ions. The results showed that low viscosity chitosan has the highest adsorption capacity among the low, middle and high viscosity chitosans. The amounts of adsorbed metal ions decreased with increased adsorption temperature and decreased pH value. The highest adsorbed amount at the equilibrium time (7.5mg/g) of Cu2+was observed among Cu2+, Pb2+, Zn2+and Ni2+.

Removal of heavy metal ions (Cu2+, Pb2+and Ni2+) from aqueous solution by raw and modified diatomite was investigated in a batch reactor. The diatomite was modified by acid-wash and base-wash, respectively. The influence of kind of diatomite, contact time and initial concentration of metal ions on the adsorption efficiency were studied. The results showed that the acid-washed diatomite showed the best adsorption capacity for all of Cu2+, Pb2+and Ni2+) among raw, acid-washed and base-washed diatomites. Metal ions adsorption amount on A-diatomite increased in the initial concentration range from 10 to 50ppm and in general kept constant after the initial concentration was higher than 60ppm. The result also indicated that Ni2+is more easily adsorbed on the surface of diatomite than Pb2+and Cu2+.

Adsorption-catalytic oxidation of terephthalic acid (TA) from waster water using modified diatomite adsorbent was studied in this paper. Two diatomites were chosen for adsorbents and TA was used as a model compound. The process consists of physic adsorption of TA and catalytic oxidation of TA. The concentration of TA was determined by UV spectrometry. The results indicate that adsorption capacity of diatomite increased with the decrease of pH value of waster water. The equilibrium adsorbed amount of modified diatomite increased with the increase of metal content in the initial metal content range from 0 to 5% for both of Ni, Fe and Cu modified diatomite, and then the equilibrium adsorbed amount decreased after 5% metal content for Ni modified diatomite and in general kept constant for Fe and Cu modified diatomite. The maximum amount of TA adsorbed at the equilibrium stage was 4.40mg/g for Ni-5/RD. The adsorption capacity of raw and modified diatomite decreased obviously with the increase of cycle number in the initial first-fourth of cycle and then decreased very slowly in the 5th-10th of cycle. The Qe of Ni-5/RD, Fe-5/RD, Cu-5/RD and RD in the 10th cycle were 3.12, 2.44, 1.87 and 0.12mg/g, respectively. The result indicated that the modified could be repeatedly used and maintained the adsorption/regeneration performance stably through many batches of operation.

Currently, environmental contamination by polybrominated diphenyl ethers (PBDEs) in the world is of important concern and requires the effective remediation technologies. The degradation of decabromodiphenyl ether (BDE-209) in the supercritical n-hexane by zerovalent iron was studied in this work. The results showed that BDE-209 can be rapidly reduced into nona-, octa-, hepta-and lower brominated polybrominated diphenyl ethers (PBDEs) under the supercritical reaction conditions. Among n-hexane, methanol, tetrahydrofuran and mixed n-hexane+ tetrahydrofuran solvents, the conversion of BDE-209 in tetrahydrofuran was the highest. BDE-209 conversion increased with increased reaction temperature and pressure. Under the reaction condition: temperature: 523K; pressure: 3.2Mpa; reaction time: 10min; reaction system: 200ml 50mg BDE-209/L n-hexane; atmosphere: N2and catalyst load: 2g/L, the conversion of BDE-209 was as high as 88.9%.