Transcript Slide 1
MODIFIED CLAY SORBENTS FOR WASTEWATER TREATMENT AND IMMOBILIZATION OF HEAVY METALS IN SOILS Juris Burlakovs, Maris Klavins, Zane Vincevica-Gaile, and Mara Stapkevica University of Latvia UNIVERSITY OF LATVIA Faculty of Geography and Earth Sciences Geography Geology Environment Department of Environmental Science 2 TOPICALITY BALTIC SEA GULF OF RIGA RUSSIA ESTONIA LATVIA There are many contaminated sites with heavy metals, also in Latvia! LITHUANIA BELARUS Heavy metals in large doses are toxic to environment and human beings 3 ENVIRONMENTAL CASES Legislation normatives in Latvia Element Cd As Ni Cr Cu Zn Pb Hg 0,08 2 3 4 4 16 13 0,25 Precaution B, mg kg-1 3 10 50 150 30 250 75 2 Critical C*, mg kg-1 8 40 200 350 150 700 300 10 Boundary values Target A, mg kg-1 *Regarding legislation in Latvia on soil quality Freeport contaminated soil site, mg kg-1 Cd As Ni Cr Cu Zn 2,3 255 10,9 9,4 1145 1455 Pb Hg 620 10,9 4 HOW TO DO THAT??? SOIL REMEDIATION METHODS Barriers and Treatment Walls Chemical Treatment Soil Amendments: Clay? Soil Washing Stabilization / Solidification (S/S technologies) Vitrification Separation / Concentration Process Electrokinetic Methods Soil Vapor Extraction & Air Sparging (for VOC’s most) Soil Flushing Bioremediation Phytoremediation 5 CLAY • Crystalline hydrated alumosilicate with cage-like structure • High internal and external surface area with a negative charge neutralized by exchange cations • Can be suggested as an heavy metal ion removal agent due to its cost-effectiveness and high efficiency 6 CLAY APPLICATIONS 7 DEVONIAN CLAY IN LATVIA 8 QUATERNARY CLAY IN LATVIA 9 SCOPE OF THE STUDIES • Optimal removal of heavy metal ions from aqueous medium can be achieved by adsorption process considered having best efficiency • The aim is to create good sorbent materials from clay for wastewater treatment and immobilization of heavy metals in soil 10 TASKS • To modify illite clay by protonation, with Ca and Na salts and hydroxyapatite • To determine physical-chemical properties important for sorption – HAp modification as an example • To perform batch kinetic experiments for lead (II) sorption • To analyze and compare sorption kinetics of modified clay and raw clay 11 Field work BALTIC SEA Experimental work Analytical work Sorption kinetics GULF OF RIGA LATVIA RUSSIA ESTONIA LITHUANIA BELARUS Lielauce Quaternary clay deposit 1.1-5.3 m thick, dominantly illitic, clayey fraction (<0.005 mm) varies 36-43 % 12 Field work Experimental work Analytical work Sorption kinetics 8 g of clay 30ml DI water 10ml (1M) CaCl2 12h for swelling KH2PO4 is added to get Ca/P calculated proportions pH 9.0 with NH4OH (1M) 12h decanting and washing with D/I water until neutral Ethanol for final removal of salts Temperature 105ºC until liquid evaporated Gallenkamp Plus II at temperature 45C for 8h 13 Field work Experimental work Analytical work Sorption kinetics Powder X-Ray Difractometry (PXRD) Scanning Electron Microscopy (SEM) thin layer of gold and palladium powder ion coater (JB-3, Eiko, Japan) Brunauer–Emmett–Teller (BET) test nitrogen multilayer adsorption Micromeritics instrument:Gemini2360 14 Field work Experimental work Analytical work Sorption kinetics Clay sorption capacity 2.5 mmol L-1 methylene blue for 0.3 g of clay suspensions were shaken for 24 h centrifuged The changes in adsorbate (methylene blue) Yenway spectrophotometer (l=1 cm, =664 nm) 15 Field work Experimental work Analytical results Sorption kinetics • BET surface for modified clay becomes 2...3 fold larger comparing to raw clay • Methylene blue analysis show significant increase in cation base saturation value • Physical chemical properties such as specific surface and BET surface show the immobilization potential regarding heavy metals in aqueous medium or soil 16 Field work Experimental Analytical results Sorption kinetics 17 Field work Experimental Analytical results Sorption kinetics 18 Field work Experimental Analytical work Sorption experiment 50 mL of 100 mg L-1 Pb (II) solution – 0.025g sorbent 5, 15, 30, 60, 180, 360, 480 and 1440 minutes filtered and analyzed for residual lead content by FAAS 19 Field work Experimental work Analytical work Sorption kinetics Lead sorption by Lielauce clay raw, protonated, modified with Ca and Na salts, hydroxyapatite 20 NOVELTY • Innovative clay sorbents produced from local resources can be offered for applied remediation – hydroxyapatite modified clay as potential sorbent has not been studied before • Data on physical-chemical properties of hydroxyapatite modified Quaternary clay give contribution to information on potential use of clay resources 21 SUMMARY • Pilot kinetic tests have shown that most effective results for lead sorption from aqueous spiked solution under natural conditions were achieved by using hydroxyapatite and Ca salts modified clay • Sorption reached 138 and 82 mg of lead for gram of HAp and Ca salt modified clay sorbent thus exceeding the result achieved by raw clay 3.5...4.5 times • SEM and PXRD patterns approve that hydroxyapatite crystals were produced in clay structure 22 From the Lab to Remedial Decisions...??? Towards more studies… 23 Paldies par uzmanību! THANK YOU FOR ATTENTION! • • • 02.05.2014 Juris Burlakovs© [email protected]