Acid Mine drAinAge ( AMd ) MAnAgeMent 285 Acid Mine drAinAge ( AMd ) MAnAgeMent
AMd is recognized as one of the most serious environmental problem in the mining industry. the problem of acid mine drainage (AMd) has been present since mining activity began thousands of years ago. Mining activity has disrupted the hydrology of mining areas so badly that it is extremely difficult to predict where water would eventually re-emerge. its causes, treatment have become the focus of number of researchers. this paper describes Acid Mine drainage (AMd) generation and its associated pollution. Jr. of Industrial Pollution Control 23 (2)(2007) pp 285-297
Removal of Uranium from Aqueous Solutions using Ammonium-modified Zeolite
Batch experiments were conducted to study the effects of contact time, pH (3 to 8), initial concentration, presence of carbonate, sulphate, and competing ions (Fe 3+ , Ca 2+ , Sr 2+ , Mg 2+ ) on the adsorption of U(VI) on ammonium-modified zeolite (AMZ). The structural features of the modified zeolite were assessed by Fourier Transform Infra Red Spectroscopy (FTIR) while the metal content was determined by Inductively Coupled Plasma Optical Emission Specroscopy (ICP-OES). The removal of uranium was effective and maximal under acidic conditions (pH 3 to 5). The kinetics of adsorption of U-nitrate and U-sulphate on AMZ were described by the pseudo-second-order model (R 2 ≥ 0.9820). In the presence of SO 4 2- and CO 3 2- , a significant reduction of 67.88 % and 71.63 %, respectively, in uranium uptake was observed. The distribution coefficient, KD (L g -1 ), was in the order of: U-nitrate (1.116) > U-sulphate (0.029) > U-carbonate (0.019), suggesting that AMZ had a high affinity for U-nitrate. The presence of Fe 3+  enhanced the removal of U(VI) from U-nitrate, U-sulphate and U-carbonate by 20.18 %, 72.48%and 82.43 %, respectively, while the presence of Ca 2+ , Mg 2+ and Sr 2+ reduced the removal to 19.57 %, 31.60 % and 23.65 %, respectively. AMZ is an effective adsorbent for uranium removal from aqueous solutions dominated by nitrate, carbonate and sulphate. KEYWORDS  Adsorption, zeolite-ammonium, uranyl, carbonate, sulphate, nitrate, aqueous solutions.
USE OF PASSIVE ANOXIC LIMESTONE DRAINS TO ENHANCE PERFORMANCE OF ACID DRAINAGE TREATMENT WETLANDS
Constructed wetlands for treating acid drainage are preferred, low-cost, alternatives to conventional treatment. Drainage with high Fe (e.g., >50 mg/1) and zero alkalinity has not been amenable to treatment with wetlands alone, primarily due to Fe hydrolysis and resultant low pH which requires chemical treatment. Anoxic limestone drains (ALDs) increase the alkalinity of seepage that is then routed to a constructed wetlands. Increased alkalinity buffers the wetlands system from pH decreases, and enhances the effectiveness of wetlands treatment. The Tennessee Valley Authority has modified two low-pH constructed wetlands with ALDs. Results indicate retrofitted wetlands· function at efficiencies meeting effluent limitations without chemical treatment. Designs of 'ALDs are site-specific, but generically consist of an excavated seepage-interception trench backfilled with crushed limestone covered with plastic and clay soil. Dissolution rates of limestone in operational and simulated ALDs were experimentally measured in attempts to estimate design parameters and longevity of an ALO. Potential problems with ALDs include structural and hydraulic stability, plugging due to reaction products within the ALO, and inadequate design and installation. Additional