Abiotic reduction of Cr(VI) by humic acids derived from peat and lignite: kinetics and removal mechanism.

Hexavalent chromium contamination of groundwater is a worldwide problem caused by anthropogenic and natural processes. We report the rate of Cr(VI) removal by two humic acids (extracted from Miocene age lignite and younger peat soil) in aqueous suspensions across a pH range likely to be encountered in terrestrial environments. Cr(VI) was reduced to Cr(III) in a first-order reaction with respect Cr(VI) concentration, but exhibited a partial order (~ 0.5) with respect to [H+]. This reaction was more rapid with the peat humic acid, where Cr(VI) reduction was observed at all pH values investigated (3.7 ≤ pH ≤ 10.5). 13C NMR and pyrolysis GC-MS spectroscopy indicate that the reaction results in loss of substituted phenolic moieties and hydroxyl groups from the humic acids. X-ray absorption spectroscopy indicated that at all pH values the resulting Cr(III) was associated with the partially degraded humic acid in an inner-sphere adsorption complex. The reaction mechanism is likely to be controlled by ester formation between Cr(VI) and phenolic/hydroxyl moieties, as this initial step is rapid in acidic systems but far less favourable in alkaline conditions. Our findings highlight the potential of humic acid to reduce and remove Cr(VI) from solution in a range of environmental conditions.

An unusual cause of factitious arthritis.

Septic arthritis and toxic synovitis are clinical conditions that can develop in association with various causes and involve symptoms such as pain, swelling, redness, sensitivity and restricted movement in the joint. A 42-year-old male presented to the emergency department with severe joint pain and nausea after injecting a 1-cc mixture of turpentine oil, eucalyptus oil, mint oil and thyme oil, which he purchased from an alternative medicine store, into his right knee with a syringe because of chronic knee pain. Ballottement and sensitivity were present at physical examination. Knee puncture yielded 60 cc of cloudy fluid. There was no growth in the material obtained. Improvement was observed following subsequent arthroscopic washing of the joint space and IV antibiotherapy, and the patient was discharged on day 21 of hospitalization with oral antibiotic and analgesic therapy. Intra-articular injection of foreign bodies into the knee joint space for therapeutic purposes, as in this case report, is a very rare occurrence, but may lead to potentially complicated arthritis.