Geotechnical, Chemical and Structural Characterization of Waste Clay from Boron Production

Turkey has 72% of the world boron reserves and takes first place with a reserve of 1.8 million tons. Each year, 900,000 tons of waste clay results from boron production. For this reason, there is a growing interest to develop novel products based on this kind of waste. In this study, geotechnical, chemical and structural characterization of waste clay from boron enterprises was performed to investigate the potential use in landfills. For this purpose, waste clay was obtained from Eskişehir Kırka Boron Works and it was characterized by using geotechnical (water content, specific weight, liquid limit, plastic limit, standard proctor compaction test, unconfined compressive strength tests, sieve analysis, hydrometer test, hydraulic conductivity), chemical and structural (cation exchange capacity (CEC), XRD, XRF, ICP-MS, SEM, FT-IR, BET) analyses. According to the results, the waste clay had a water content of 39.2% and a specific weight of 2.77 g/cm3 . According to liquid limit (58%) and plastic limit (30%) values, plasticity index was calculated as to be 28%. The standard proctor compaction test showed that the most effective compression ratio was obtained at the optimum water content of 33%. The unconfined compressive strength was 2.16 kg/cm2 , the swelling potential was 10.4% and the permeability constant was obtained as 3.5×10-11 m/s at 33% water content. Soil classification was determined as to be high-plasticity clay (CH) according to the results of sieve analysis, hydrometer test, liquid and plastic limit tests. CEC of the clay was 55 meq /100 g waste clay. The results of XRD, XRF, ICP-MS and FT-IR analyses have proven that the waste clay is mostly composed of dolomite, magnesium oxide, tincal and quartz. BET analysis showed that the specific surface area of the clay is 5.12±0.1 m2 /g. These characterization data will form a background for further studies regarding potential uses of the waste clay in solid waste landfill sites.