Kinetics of arsenic (As) removal by Proteus mirabilis and Bacillus subtilis were studied using the non-linear error functions approach. The two microorganisms (from soils samples obtained from a contaminated site in Amaonye-Ishiagu in Ebonyi State of Nigeria) were cultured and employed to deplete the metal ion from the contaminated soils. The experimental data were studied with four kinetic models namely pseudo first order, pseudo second order, simple Elovich, and intraparticle diffusion models using some non-linear error functions of root mean square error (RMSE), standard error of experiment (SEE), average relative error (ARE) and normalized standard deviation (NSD). Data from removal by both organisms were best described with pseudo first order model indicated by the ARE of minimum value of -1.8728 for Proteus mirabilis, and -2.1208 for Bacillus subtilis. These showed that the removal mechanism was reaction controlled as chemisorption was the rate limiting step.
Detailed investigation of the geotechnical properties of borrow pits soils, used for road and other construction works in major Niger Delta communities of Nigeria was carried out. The particle size distribution, specific gravity, liquid limit (LL), plastic limit (PL), plasticity index (PI), maximum dry density (MDD), optimal moisture content (OMC), free swelling index (FSI) and Californian bearing ratio (CBR) of the sampled soil were measured in accordance with the British Standard (BS) code and America Standard Testing Material (ASTM) code. Based on the Unified Soil Classification System (USCS), the borrow pits soil can be classified as poorly graded sand with clay. Also, the results depicted that the borrow pits soil Specific gravity, LL, PI values and PL valued ranged from 2.6-2.71, 21.1% -34.08%, 6.29%-13.58% and 15.81% - 20.23%, respectively. OMC, MDD and CBR ranged from 14.53%-15.17%, 1.53 kg/m3 -1.69 kg/m3 and 20.19% -47.15%, respectively. The study affirmed that some of the soils can be useful for the construction of roads and other civil engineering structures, without stabilization.
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