Soluble_JJ metals_NN2 in_II coal_NN1 gasification_NN1 residues_NN2 1_MC1 ._. 
Introduction_NN1 The_AT By-Product_NN1 Utilization_NN1 Team_NN1 at_II the_AT National_JJ Energy_NN1 Technology_NN1 Laboratory_NN1 (_( NETL_NP1 )_) of_IO the_AT US_NP1 Department_NN1 of_IO Energy_NN1 has_VHZ conducted_VVN column_NN1 leaching_VVG tests_NN2 to_TO characterize_VVI the_AT release_NN1 of_IO various_JJ cations_NN2 ,_, particularly_RR heavy_JJ metals_NN2 ,_, from_II coal_NN1 utilization_NN1 by-products_NN2 (_( CUB_NN1 )_) ._. 
These_DD2 data_NN have_VH0 been_VBN used_VVN to_TO relate_VVI the_AT solubility_NN1 of_IO various_JJ cations_NN2 to_II their_APPGE concentration_NN1 in_II the_AT solid_JJ CUB_NN1 ,_, to_II the_AT pH_NN1 of_IO the_AT leachant_NN1 ,_, to_TO silicate/non-silicate_VVI speciation_NN1 ,_, and_CC to_II the_AT alkalinity_NN1 of_IO the_AT CUB_NN1 ._. 
The_AT majority_NN1 of_IO the_AT samples_NN2 tested_VVN at_II NETL_NP1 have_VH0 been_VBN class_NN1 F_ZZ1 fly_JJ ashes_NN2 from_II pulverized_JJ coal_NN1 (_( PC_NNU )_) power_NN1 plants_NN2 ._. 
The_AT chemical_NN1 and_CC physical_JJ characteristics_NN2 of_IO the_AT residues_NN2 from_II other_JJ types_NN2 of_IO power_NN1 plants_NN2 will_VM influence_VVI their_APPGE utilization_NN1 options_NN2 and_CC disposal_NN1 scenarios_NN2 ._. 
The_AT objective_NN1 of_IO this_DD1 study_NN1 was_VBDZ to_TO determine_VVI the_AT release_NN1 of_IO metals_NN2 from_II the_AT residues_NN2 generated_VVN at_II three_MC integrated_JJ gasification_NN1 combined_JJ cycle_NN1 (_( IGCC_NP1 )_) installations_NN2 ._. 
IGCC_NP1 power_NN1 systems_NN2 can_VM supply_VVI stable_JJ ,_, affordable_JJ ,_, and_CC high-efficiency_JJ energy_NN1 with_IW minimal_JJ environmental_JJ impact_NN1 ._. 
The_AT technology_NN1 is_VBZ both_RR fuel_NN1 and_CC product_NN1 flexible_JJ ,_, and_CC it_PPH1 typically_RR emits_VVZ very_RG low_JJ levels_NN2 of_IO the_AT criteria_NN2 pollutants_NN2 associated_VVN with_IW PC_NN1 combustion_NN1 ,_, including_II SO2_FO ,_, NOx_NP1 and_CC particulates_NN2 ._. 
As_II21 of_II22 2007_MC ,_, there_EX were_VBDR 138_MC IGCC_NN1 plants_NN2 worldwide_RL ;_; 55%_NNU of_IO this_DD1 capacity_NN1 is_VBZ coal_NN1 fired_VVD ._. 
Electric_JJ power_NN1 represents_VVZ 18%_NNU of_IO the_AT products_NN2 ._. 
There_EX are_VBR currently_RR two_MC commercial_JJ IGCC_NN1 power_NN1 plants_NN2 in_II the_AT US_NP1 ._. 
Eleven_MC additional_JJ IGCC_NN1 power_NN1 plants_NN2 ,_, under_II consideration_NN1 in_II the_AT US_NP1 ,_, will_VM also_RR utilize_VVI coal_NN1 or_CC coal/pet_NN1 coke_NN1 blends_NN2 ._. 
Although_CS economic_JJ and_CC technical_JJ factors_NN2 have_VH0 slowed_VVN the_AT growth_NN1 of_IO IGCC_NN1 in_II the_AT US_NP1 ,_, many_DA2 believe_VV0 that_CST this_DD1 technology_NN1 represents_VVZ the_AT future_NN1 in_II coal-based_JJ power_NN1 systems_NN2 ._. 
With_IW support_NN1 from_II DOE_NP1 ,_, commercial-scale_JJ ,_, coal_NN1 gasification-based_NN1 power_NN1 systems_NN2 have_VH0 been_VBN successfully_RR demonstrated_VVN in_II the_AT US_NP1 ._. 
Under_II pressure_NN1 in_II the_AT gasifier_NN1 ,_, heat_NN1 in_II the_AT presence_NN1 of_IO steam_NN1 and_CC oxygen_NN1 converts_VVZ carbonaceous_JJ feedstock_NN1 into_II syngas_NN2 (_( H2_FO and_CC CO_FO )_) ,_, along_II21 with_II22 smaller_JJR quantities_NN2 of_IO CO2_FO and_CC CH4_FO ._. 
In_II IGCC_NP1 ,_, the_AT syngas_NN2 is_VBZ used_VVN to_TO generate_VVI electric_JJ power_NN1 ._. 
It_PPH1 can_VM also_RR be_VBI used_VVN as_II a_AT1 source_NN1 of_IO hydrogen_NN1 ,_, and_CC a_AT1 broad_JJ range_NN1 of_IO chemicals_NN2 and_CC clean_JJ fuels_NN2 ._. 
IGCC_NP1 combines_VVZ coal_NN1 gasification_NN1 with_IW gas_NN1 turbine_NN1 and_CC steam_NN1 turbine_NN1 power_NN1 generation_NN1 ._. 
IGCC_NP1 is_VBZ one_MC1 of_IO the_AT most_RGT efficient_JJ and_CC cleanest_JJT of_IO available_JJ technologies_NN2 for_IF coal-based_JJ power_NN1 generation_NN1 ,_, with_IW emissions_NN2 comparable_JJ to_II those_DD2 of_IO natural_JJ gas_NN1 power_NN1 production_NN1 ._. 
Depending_II21 on_II22 the_AT system_NN1 ,_, minerals_NN2 (_( ash_NN1 )_) in_II the_AT feedstock_NN1 separate_JJ and_CC leave_VV0 the_AT bottom_NN1 of_IO the_AT gasifier_NN1 as_II a_AT1 glass-like_JJ slag_NN1 ._. 
A_AT1 fraction_NN1 of_IO the_AT ash_NN1 may_VM become_VVI entrained_VVN in_II the_AT syngas_NN2 and_CC require_VVI removal_NN1 downstream_RL ._. 
Other_JJ pollutants_NN2 can_VM be_VBI recovered_VVN as_CSA saleable_JJ materials_NN2 ,_, such_II21 as_II22 sulfur_NN1 or_CC sulfuric_JJ acid_NN1 and_CC ammonia_NN1 ._. 
IGCC_NP1 can_VM accommodate_VVI a_AT1 wide_JJ range_NN1 of_IO feedstocks_NN2 ,_, including_II coal_NN1 and_CC low-cost_JJ opportunity_NN1 fuels_NN2 ,_, such_II21 as_II22 petroleum_NN1 coke_NN1 ,_, biomass_NN1 ,_, and_CC municipal_JJ wastes_NN2 ._. 
The_AT CUB_NN1 research_NN1 program_NN1 at_II NETL_NP1 has_VHZ determined_VVN the_AT release_NN1 of_IO cations_NN2 from_II a_AT1 random_JJ population_NN1 of_IO over_RG 50_MC class_NN1 F_ZZ1 fly_JJ ash_NN1 samples_NN2 from_II PC_NN1 power_NN1 plants_NN2 ._. 
The_AT intent_NN1 was_VBDZ to_TO identify_VVI general_JJ trends_NN2 and_CC environmental_JJ controls_NN2 on_II metal_NN1 leachability_NN1 ._. 
For_IF this_DD1 study_NN1 of_IO IGCC_NN1 samples_NN2 ,_, the_AT intent_NN1 was_VBDZ again_RT to_TO obtain_VVI a_AT1 random_JJ group_NN1 of_IO IGCC_NP1 residue_NN1 samples_NN2 and_CC to_TO focus_VVI on_II conditions_NN2 ,_, such_II21 as_II22 the_AT concentration_NN1 of_IO heavy_JJ metals_NN2 ,_, the_AT pH_NN1 of_IO the_AT leachant_NN1 ,_, the_AT volume_NN1 of_IO leachant_NN1 ,_, and_CC the_AT alkalinity_NN1 of_IO the_AT sample_NN1 ,_, that_CST affect_VV0 the_AT release_NN1 of_IO cations_NN2 ._. 
For_IF this_DD1 study_NN1 ,_, nine_MC samples_NN2 of_IO IGCC_NN1 residues_NN2 were_VBDR obtained_VVN from_II three_MC sources_NN2 ._. 
Two_MC samples_NN2 were_VBDR generated_VVN in_II the_AT fluidized_JJ bed_NN1 gasifier_NN1 at_II the_AT DOE_NP1 's_GE Power_NN1 Systems_NN2 Development_NN1 Facility_NN1 (_( PSDF_NP1 )_) in_II Wilsonville_NP1 ,_, AL_NP1 ._. 
Although_CS the_AT gasifier_NN1 at_II the_AT PSDF_NP1 ,_, a_AT1 circulating_JJ fluidized_JJ bed_NN1 ,_, is_VBZ designed_VVN to_TO gasify_VVI a_AT1 variety_NN1 of_IO fuels_NN2 ,_, the_AT samples_NN2 sent_VVN to_TO NETL_VVI were_VBDR produced_VVN from_II sub-bituminous_JJ coal_NN1 ._. 
The_AT samples_NN2 were_VBDR particulates_NN2 removed_VVN with_IW a_AT1 hot_JJ gas_NN1 filter_NN1 ._. 
The_AT other_JJ seven_MC samples_NN2 were_VBDR derived_VVN from_II mixtures_NN2 of_IO coal_NN1 and_CC pet_NN1 coke_NN1 ._. 
One_PN1 was_VBDZ generated_VVN during_II a_AT1 start-up_JJ test_NN1 of_IO a_AT1 gasifier_NN1 burning_JJ coal_NN1 or_CC pet_NN1 coke_NN1 in_II a_AT1 fluidized_JJ bed_NN1 containing_VVG limestone_NN1 ._. 
Two_MC sets_NN2 of_IO three_MC samples_NN2 (_( a_AT1 slag_NN1 and_CC two_MC high_JJ carbon_NN1 particulates_NN2 )_) were_VBDR obtained_VVN from_II a_AT1 commercial_JJ gasifier_NN1 using_VVG coal_NN1 and_CC pet_NN1 coke_NN1 ._. 
While_CS not_XX extensive_JJ ,_, this_DD1 set_NN1 of_IO samples_NN2 includes_VVZ residues_NN2 typically_RR generated_VVN in_II IGCC_NP1 plants._NNU 2_MC ._. 
Methods_NN2 and_CC materials_NN2 2.1_MC ._. 
Leaching_VVG system_NN1 The_AT NETL_NN1 column_NN1 leaching_VVG system_NN1 was_VBDZ designed_VVN to_TO simulate_VVI the_AT reaction_NN1 of_IO granular_JJ materials_NN2 during_II exposure_NN1 to_II fluids_NN2 such_II21 as_II22 landfill_NN1 leachate_NN1 ,_, acid_NN1 rain_NN1 ,_, or_CC acid_NN1 mine_NN1 drainage_NN1 ._. 
The_AT columns_NN2 were_VBDR constructed_VVN of_IO 1_MC1 m_NNO sections_NN2 of_IO 5_MC cm_NNU ID_NN1 acrylic_NN1 pipe_NN1 with_IW an_AT1 approximate_JJ volume_NN1 of_IO 2_MC L._NNU Each_DD1 column_NN1 held_VVD a_AT1 representative_NN1 0.5-1_MCMC kg_NNU sample_NN1 of_IO unconsolidated_JJ material_NN1 with_IW a_AT1 particle_NN1 diameter_NN1 of_IO less_DAR than_CSN 0.5_MC cm_NNU ._. 
Threaded_JJ PVC_NN1 pipe_NN1 caps_NN2 closed_VVD each_DD1 end_NN1 ;_; 1/4-in_FU NPT_NP1 fittings_NN2 were_VBDR tapped_VVN into_II the_AT ends_NN2 for_IF leachant_JJ inflow_NN1 and_CC leachate_JJ outflow_NN1 ._. 
Ten_MC grams_NNU2 of_IO glass_NN1 wool_NN1 was_VBDZ placed_VVN in_II the_AT bottom_NN1 of_IO the_AT column_NN1 before_II the_AT sample_NN1 was_VBDZ poured_VVN into_II the_AT column_NN1 ;_; another_DD1 10_MC g_NNU of_IO glass_NN1 wool_NN1 was_VBDZ placed_VVN on_II31 top_II32 of_II33 the_AT sample_NN1 ._. 
The_AT sealed_JJ column_NN1 was_VBDZ hung_VVN on_RP a_AT1 distillation_NN1 rack_NN1 ._. 
Four_MC different_JJ CUB_NN1 samples_NN2 could_VM be_VBI leached_VVN in_II each_DD1 test_NN1 ._. 
To_TO cover_VVI the_AT acid/alkaline_JJ range_NN1 of_IO natural_JJ conditions_NN2 ,_, five_MC leachant_JJ solutions_NN2 ,_, listed_VVN in_II Table_NN1 1_MC1 ,_, were_VBDR used_VVN in_II each_DD1 test_NN1 ._. 
A_AT1 peristaltic_JJ pump_NN1 delivered_VVD leachant_JJ solution_NN1 from_II a_AT1 20_MC L_ZZ1 reservoir_NN1 to_II individual_JJ delivery_NN1 lines_NN2 for_IF each_DD1 column_NN1 ._. 
The_AT flow_NN1 rate_NN1 was_VBDZ approximately_RR 130_MC mL/d_FU ._. 
Leachate_NN1 was_VBDZ collected_VVN in_II 1_MC1 L_ZZ1 volumetric_JJ cylinders_NN2 and_CC analyzed_VVD at_II 2-3_MCMC day_NNT1 intervals._NNU 3_MC ._. 
Results_NN2 3.1_MC ._. 
Buffering_VVG capacity_NN1 Work_NN1 at_II NETL_NN1 with_IW a_AT1 random_JJ group_NN1 of_IO PC_NN1 fly_NN1 ash_NN1 samples_NN2 has_VHZ shown_VVN that_CST most_DAT are_VBR alkaline_JJ ,_, and_CC that_DD1 fly_NN1 ash_NN1 alkalinity_NN1 buffers_VVZ the_AT pH_NN1 of_IO leachate_NN1 ._. 
Several_DA2 heavy_JJ metals_NN2 are_VBR usually_RR not_XX released_VVN from_II the_AT fly_NN1 ash_NN1 until_CS the_AT leachate_JJ pH_NN1 is_VBZ less_DAR than_CSN five_MC ._. 
The_AT pH_NN1 of_IO leachates_NN2 from_II acidic_JJ PC_NN1 samples_NN2 tested_VVD was_VBDZ generally_RR in_II the_AT acid_NN1 range_NN1 ._. 
Buffering_VVG capacity_NN1 in_II PC_NN1 samples_NN2 has_VHZ been_VBN related_VVN to_II the_AT non-silicate_JJ Ca_NP1 concentration_NN1 ._. 
In_II the_AT IGCC_NN1 samples_NN2 ,_, the_AT concentration_NN1 of_IO Ca_NP1 in_II the_AT SPPP_NP1 and_CC PSDF_NP1 samples_NN2 is_VBZ typical_JJ of_IO FBC_NP1 by-products_NN2 in_II which_DDQ the_AT high_JJ median_JJ leachate_JJ pH_NN1 is_VBZ related_VVN to_II the_AT dissolution_NN1 of_IO unreacted_JJ CaCO3_FO ._. 
The_AT concentration_NN1 of_IO Ca_NP1 is_VBZ much_RR lower_JJR in_II the_AT TFines_NP2 ,_, TFuel_NP1 and_CC TSlag_NP1 IGCC_NP1 samples_NN2 ._. 
The_AT median_JJ leachate_JJ pH_NN1 for_IF these_DD2 samples_NN2 is_VBZ in_II the_AT neutral_JJ to_II acid_NN1 range_NN1 ,_, and_CC does_VDZ not_XX indicate_VVI a_AT1 distinctive_JJ relationship_NN1 to_II the_AT Ca_NP1 concentration_NN1 in_II the_AT sample_NN1 ._. 
The_AT intent_NN1 of_IO using_VVG several_DA2 leaching_VVG solutions_NN2 is_VBZ to_TO determine_VVI metal_NN1 solubility_NN1 with_IW variation_NN1 in_II pH_NN1 ._. 
In_II an_AT1 unbuffered_JJ solution_NN1 ,_, the_AT pH_NN1 of_IO the_AT leachate_NN1 would_VM remain_VVI close_RR to_II that_DD1 of_IO the_AT leachant_NN1 ._. 
TFuel2_FO and_CC TSlag2_FO also_RR show_VV0 little_RR buffering_VVG capacity_NN1 ._. 
The_AT TFines2_FO sample_NN1 is_VBZ acidic_JJ ,_, as_CSA is_VBZ the_AT TSlag1_FO sample_NN1 ;_; the_AT pH_NN1 of_IO all_DB leachates_NN2 ,_, except_CS Na2CO3_FO ,_, is_VBZ less_DAR than_CSN five_MC ._. 
Both_DB2 PSDF_NP1 and_CC the_AT SPPP_NP1 samples_NN2 are_VBR strongly_RR alkaline_JJ ,_, the_AT pH_NN1 of_IO all_DB leachate_JJ samples_NN2 ,_, including_II those_DD2 from_II acid_NN1 leachants_NN2 ,_, is_VBZ greater_JJR than_CSN six_MC ._. 
For_IF all_DB the_AT IGCC_NN1 samples_NN2 ,_, after_CS an_AT1 initial_JJ adjustment_NN1 ,_, the_AT pH_NN1 of_IO all_DB the_AT leachates_NN2 remained_VVD relatively_RR constant_JJ ,_, and_CC leaching_NN1 was_VBDZ completed_VVN within_II a_AT1 relatively_RR narrow_JJ pH_NN1 range_NN1 ._. 
For_IF the_AT acidic_JJ samples_NN2 ,_, the_AT median_JJ leachate_JJ pH_NN1 in_II neutral_JJ and_CC acid_NN1 leachants_NN2 was_VBDZ less_DAR than_CSN seven_MC and_CC the_AT pH_NN1 range_NN1 was_VBDZ on_II the_AT order_NN1 of_IO two_MC pH_NN1 units_NN2 ._. 
The_AT alkaline_JJ samples_NN2 had_VHD a_AT1 higher_JJR median_JJ pH_NN1 ,_, but_CCB the_AT leachate_JJ pH_NN1 range_NN1 was_VBDZ also_RR on_II the_AT order_NN1 of_IO two_MC pH_NN1 units._NNU 3.2_MC ._. 
Release_NN1 of_IO metal_NN1 ions_NN2 from_II IGCC_NP1 residues_NN2 In_II several_DA2 leaching_VVG studies_NN2 of_IO PC_NN1 fly_NN1 ashes_NN2 ,_, most_RGT metallic_JJ ions_NN2 were_VBDR more_RGR soluble_JJ in_II acid_NN1 leachants_NN2 ,_, while_CS those_DD2 that_CST formed_VVD oxyanions_NN2 were_VBDR more_RGR soluble_JJ in_II alkaline_JJ leachants_NN2 ._. 
With_IW some_DD exceptions_NN2 ,_, this_DD1 was_VBDZ also_RR true_JJ for_IF the_AT acidic_JJ IGCC_NN1 residues_NN2 ._. 
The_AT ions_NN2 Al_NP1 ,_, Be_VBI ,_, Ca_NP1 ,_, Cr_NP1 ,_, Cu_FO ,_, Fe_NP1 ,_, Mg_NNA ,_, Mn_FO ,_, Na_UH ,_, Ni_NP1 ,_, Pb_FO ,_, and_CC Zn_NP1 were_VBDR most_RGT soluble_JJ in_II the_AT acid_NN1 leachants_NN2 ._. 
Of_IO the_AT elements_NN2 that_CST form_VV0 oxyanions_NN2 ,_, only_RR Se_ND1 was_VBDZ more_RGR soluble_JJ in_II the_AT alkaline_JJ leachant_NN1 ;_; Sb_NP1 was_VBDZ essentially_RR insoluble_JJ and_CC As_CSA was_VBDZ soluble_JJ to_II some_DD extent_NN1 in_II both_DB2 acid_NN1 and_CC alkaline_JJ leachants_NN2 ._. 
The_AT cumulative_JJ extracted_JJ concentration_NN1 was_VBDZ generally_RR of_IO the_AT same_DA order_NN1 of_IO magnitude_NN1 for_IF TFines_NN2 ,_, TFuel_NP1 ,_, and_CC TSlag_VV0 samples_NN2 ._. 
The_AT change_NN1 in_II leachate_JJ concentration_NN1 with_IW volume_NN1 for_IF the_AT elements_NN2 Ni_NP1 and_CC Zn_NP1 showed_VVD an_AT1 initially_RR high_JJ concentration_NN1 with_IW a_AT1 rapid_JJ decline_NN1 ._. 
This_DD1 pattern_NN1 indicates_VVZ the_AT dissolution_NN1 of_IO a_AT1 soluble_JJ coating_NN1 ._. 
The_AT decrease_NN1 in_II leachate_JJ concentration_NN1 occurs_VVZ in_II all_DB leachants_NN2 ,_, indicting_VVG that_CST it_PPH1 is_VBZ not_XX affected_VVN by_II the_AT leachant_NN1 or_CC leachate_JJ pH_NN1 ._. 
In_II contrast_NN1 ,_, the_AT concentration_NN1 of_IO Fe_NP1 and_CC As_CSA was_VBDZ initially_RR low_JJ ,_, but_CCB increased_VVN with_IW leachate_JJ volume_NN1 ._. 
The_AT increased_JJ concentration_NN1 with_IW cumulative_JJ leachate_JJ volume_NN1 indicates_VVZ that_CST as_II the_AT soluble_JJ surface_NN1 coating_NN1 is_VBZ removed_VVN ,_, the_AT particle_NN1 body_NN1 is_VBZ exposed_VVN to_II the_AT leachant_NN1 ,_, and_CC the_AT leachate_JJ concentration_NN1 of_IO soluble_JJ components_NN2 is_VBZ a_AT1 function_NN1 of_IO their_APPGE solid_JJ concentration_NN1 or_CC exposed_JJ surface_NN1 area_NN1 ._. 
This_DD1 pattern_NN1 was_VBDZ observed_VVN with_IW the_AT TFines_NP2 and_CC TFuel_NP1 samples_NN2 ._. 
If_CS there_EX is_VBZ no_AT soluble_JJ surface_NN1 coating_NN1 ,_, the_AT release_NN1 of_IO Ni_NP1 and_CC Zn_NP1 ,_, in_II31 addition_II32 to_II33 Fe_NP1 and_CC As_CSA ,_, is_VBZ related_VVN to_II soluble_JJ concentration_NN1 or_CC exposed_JJ surface_NN1 area_NN1 ,_, a_AT1 pattern_NN1 similar_JJ to_II that_DD1 observed_VVD in_II the_AT TSlag_NN1 samples_NN2 ._. 
The_AT distribution_NN1 of_IO trace_NN1 elements_NN2 between_II fractions_NN2 in_II fly_NN1 ash_NN1 has_VHZ been_VBN related_VVN to_II their_APPGE volatility_NN1 ._. 
Arsenic_NN1 ,_, Pb_FO ,_, Ni_NP1 ,_, and_CC Zn_NP1 are_VBR considered_VVN moderately_RR volatile_JJ elements_NN2 and_CC may_VM be_VBI found_VVN in_II fine_JJ particles_NN2 and_CC surface_NN1 layers_NN2 ._. 
However_RR with_IW the_AT TFines_NP2 and_CC TFuel_NP1 samples_NN2 ,_, As_CSA and_CC Pb_FO apparently_RR have_VH0 the_AT same_DA solubility_NN1 pattern_NN1 as_CSA the_AT non-volatile_JJ Fe_NP1 ._. 
The_AT release_NN1 of_IO metal_NN1 ions_NN2 from_II the_AT alkaline_JJ residues_NN2 (_( SPPP_NP1 ,_, PSDF1_FO ,_, and_CC PSDF2_FO )_) was_VBDZ influenced_VVN by_II the_AT relatively_RR high_JJ pH_NN1 in_II all_DB of_IO the_AT leachant_JJ solutions_NN2 ._. 
Even_RR in_II the_AT acid_NN1 leachants_NN2 ,_, the_AT lowest_JJT pH_NN1 of_IO the_AT leachate_NN1 was_VBDZ only_RR in_II the_AT neutral_JJ range_NN1 ._. 
The_AT cations_NN2 Ba_NN1 ,_, Ca_NP1 ,_, Co_NP1 ,_, Cr_NP1 ,_, Fe_NP1 ,_, Mg_NNA ,_, Mn_FO ,_, Ni_NP1 ,_, and_CC Zn_NP1 were_VBDR more_RGR soluble_JJ in_II the_AT lower_JJR pH_NN1 acid_NN1 leachants_NN2 ._. 
The_AT solubility_NN1 of_IO Be_VBI ,_, and_CC Cd_NN1 was_VBDZ low_JJ in_II all_DB leachants_NN2 ,_, while_CS K_ZZ1 and_CC Na_FW were_VBDR very_RG soluble_JJ in_II all_DB leachants_NN2 ._. 
While_CS the_AT solubility_NN1 of_IO As_RG ,_, Sb_NP1 ,_, and_CC Se_NP1 was_VBDZ low_JJ for_IF the_AT PSDF_NP1 samples_NN2 ,_, it_PPH1 was_VBDZ highest_JJT in_II the_AT high_JJ pH_NN1 leachant_NN1 which_DDQ is_VBZ typical_JJ of_IO oxyanions._NNU 3.3_MC ._. 
Mercury_NP1 The_AT Hg_FO concentration_NN1 in_II the_AT IGCC_NN1 residues_NN2 was_VBDZ less_DAR than_CSN 50_MC &mu;_NULL g/kg_NNU for_IF both_DB2 acidic_JJ and_CC alkaline_JJ samples_NN2 ,_, less_RRR than_CSN the_AT concentration_NN1 in_II fly_NN1 ashes_NN2 from_II PC_NN1 combustion_NN1 of_IO high_JJ Hg_FO coals_NN2 or_CC from_II Hg_FO capture_VV0 tests_NN2 ._. 
The_AT cumulative_JJ amount_NN1 of_IO Hg_FO leached_VVD from_II the_AT IGCC_NN1 residues_NN2 was_VBDZ less_RRR than_CSN 1_MC1 &mu;_NULL g/kg_NNU for_IF all_DB samples_NN2 ._. 
For_IF the_AT majority_NN1 of_IO samples_NN2 ,_, Hg_FO was_VBDZ most_RGT effectively_RR extracted_VVN by_II acid_NN1 leaching_VVG ._. 
On_II a_AT1 relative_JJ basis_NN1 ,_, between_II 0.01_MC and_CC 10_MC pct_NNU of_IO the_AT Hg_FO was_VBDZ extracted_VVN from_II the_AT "_" T_ZZ1 "_" samples_NN2 ._. 
Acid_NN1 leaching_VVG extracted_VVN between_II 8%_NNU and_CC 26%_NNU of_IO the_AT Hg_FO from_II the_AT PSDF_NP1 samples_NN2 ._. 
There_EX is_VBZ no_AT apparent_JJ correlation_NN1 between_II Hg_FO concentration_NN1 and_CC C_ZZ1 content_JJ ._. 
In_II the_AT high_JJ carbon_NN1 half_NN1 of_IO the_AT sample_NN1 set_NN1 ,_, acid_NN1 extraction_NN1 of_IO Hg_FO decreases_VVZ with_IW C_NP1 concentration_NN1 ._. 
There_EX is_VBZ no_AT apparent_JJ correlation_NN1 with_IW acidic_JJ or_CC alkaline_JJ samples_NN2 or_CC with_IW the_AT presence_NN1 of_IO petroleum_NN1 coke_NN1 in_II the_AT fuel._NNU 3.4_MC ._. 
Cation_NN1 concentration_NN1 versus_II drinking_VVG water_NN1 standards_NN2 The_AT release_NN1 of_IO metals_NN2 from_II CUB_NN1 is_VBZ a_AT1 concern_NN1 when_CS potential_JJ utilization_NN1 or_CC disposal_NN1 may_VM impact_NN1 surface_NN1 water_NN1 or_CC groundwater_NN1 ._. 
Although_CS the_AT column_NN1 leachate_NN1 is_VBZ not_XX a_AT1 surrogate_NN1 for_IF potable_JJ water_NN1 ,_, primary_JJ and_CC secondary_JJ drinking_NN1 water_NN1 standards_NN2 are_VBR frequently_RR applied_VVN to_TO categorize_VVI potential_JJ hazards_NN2 ._. 
In_II this_DD1 study_NN1 of_IO IGCC_NN1 residues_NN2 ,_, acid_NN1 or_CC alkaline_JJ leachants_NN2 produced_VVD concentrations_NN2 in_II the_AT leachate_NN1 that_CST exceeded_VVD drinking_VVG water_NN1 standards_NN2 by_II several_DA2 orders_NN2 of_IO magnitude_NN1 ._. 
In_II the_AT neutral_JJ leachant_NN1 ,_, although_CS the_AT PDW_NP1 standards_NN2 were_VBDR not_XX exceeded_VVN as_CSA egregiously_RR ,_, they_PPHS2 were_VBDR exceeded_VVN for_IF As_RG ,_, Ba_NP1 ,_, Be_VBI ,_, Cu_FO ,_, Pb_FO ,_, and_CC Se_ND1 ._. 
Secondary_JJ drinking_NN1 water_NN1 standards_NN2 ,_, which_DDQ are_VBR matters_NN2 of_IO taste_NN1 and_CC aesthetics_NN1 rather_II21 than_II22 health_NN1 ,_, were_VBDR exceeded_VVN by_II eight_MC of_IO the_AT nine_MC IGCC_NN1 samples._NNU 5_MC ._. 
Summary_NN1 In_II this_DD1 set_NN1 of_IO nine_MC IGCC_NP1 by-product_NN1 samples_NN2 ,_, the_AT three_MC samples_NN2 generated_VVN in_II fluidized_JJ beds_NN2 combustors_NN2 were_VBDR highly_RR alkaline_JJ ._. 
Two_MC of_IO the_AT six_MC samples_NN2 generated_VVN in_II a_AT1 commercial_JJ IGCC_NN1 unit_NN1 were_VBDR neutral_JJ and_CC had_VHD relatively_RR little_JJ effect_NN1 on_II leachate_JJ pH_NN1 ._. 
The_AT neutral_JJ and_CC acid_NN1 leachants_NN2 generated_VVD acidic_JJ leachates_NN2 from_II the_AT other_JJ four_MC samples_NN2 ._. 
In_II both_DB2 types_NN2 of_IO samples_NN2 ,_, there_EX was_VBDZ a_AT1 relatively_RR small_JJ change_NN1 in_II the_AT pH_NN1 of_IO the_AT leachate_NN1 from_II acid_NN1 ,_, neutral_JJ and_CC alkaline_JJ leachants_NN2 ._. 
