Chemical Reports

In this research, the combustion properties of the briquette produced by blending mung beans shell (MBS) with carbonized danta wood sawdust was compared with that of the briquette produced by blending MBS with uncarbonized danta wood sawdust. The briquettes wereproduced atdifferentsawdust to biomass ratios (100%:0, 70%:30%, 50%: 50%, 30%: 70% and 100%:0). Cassava starch was used as a binder. Proximate analysis (moisture content, ash content, volatile matter and fixed carbon) and combustion properties (calorific value, ignition time, burning time, burning rate, specific fuel consumption and thermal efficiency) were calculated using standard methods. The results of the analyses showed that 100% sawdust briquette samples had the lowest moisture content, 4.74±0.00 for carbonized sawdust and 6.76±0.02 for uncarbonized sawdust.100% uncarbonized and carbonized sawdust briquette samples had a fixed carbon of 68.93±0.02 and 87.46%, Ash content:3.70±0.00% and 2.18±0.04%,volatile matter: 20.61±0.00 and 5.61±0.04 and calorific value: 29.401±0.0 MJ/Kg and 32.532±0.05 MJ/Kg respectively.The ignition time increase with increase in biomass load for uncarbonized sawdust samples and decrease with increase in biomass load for carbonized sawdust briquette samples. The burning time decreased from 86±0.57mins (70% sawdust + 30% biomass) to 70±0.57mins (100% biomass) for the carbonized sawdust briquette samples and for the uncarbonized, it ranged from 68±0.00 (70% sawdust + 30% biomass) to 71.6±0.57 mins (30% sawdust + 70% biomass) and then dropped to 68±0.57(100% biomass load). The burning rate decreased in carbonizedbriquette samples and increased in uncarbonized briquette samples with increase in biomass load. The specific fuel consumption for carbonized and uncarbonized sawdust briquette sample decreased with increase in MBS load. 100% carbonized and uncarbonized sawdust briquette samples had a thermal efficiency of 8.78 and 16.47 respectively. It can be concluded that blend of carbonized sawdust and mung beans shell will make a better fuel due to better combustion properties than the uncarbonized sawdust samples.

This study was carried out to assess the extent of concentration exposure of As, Cu, Cr, Ni and Mn in the soils of five active dumpsites located at (Eliozu, Oyibo, Eneka, Eleme and Woji) in the city of Port Harcourt Rivers State, Nigeria to evaluate the pollution indices of heavy metals. Soil samples were collected randomly at the quadrant from the dumpsite while control samples were collected from farmland 25 km away from the dumpsite. Some physiochemical parameters (pH, TOC and CEC) of the soils were evaluated using standard techniques, while the heavy metal concentrations were evaluated using Atomic Absorption Spectroscopy (AAS). The pollution levels of soil heavy metals were assessed using several pollution indices. The mean concentration of heavy metals (mg/kg) ranged between As (ND – 0.45), Cr (ND – 2.21), Cu (6.05 – 51.87), Mn (3.24 – 37.91), Ni (ND – 13.50) across the studied dumpsites. The heavy metal levels in soil samples observed were in the order of Cu > Mn > Ni > Cr > As (Eleme), Cu > Mn > As > Ni > Cr (Eliozu), Cu > Mn > Ni > Cr > As (Eneka), Cu > Mn > Cr (Oyigbo), Cu > Mn > Ni > Cr > As (Woji), Cu > Mn > Ni > Cr > As (Control Site). The pH results were relatively acidic across the studied dumpsites ranging from 5.7±0.58 to 6.63± 0.02, while the TOC levels were low to moderate showing no wide disparity in the values. The Cation exchange capacity (CEC) showed a range of 13.98±0.186 (Eneka) to 20.98±0.061 cmol/kg (Woji) across the studied dumpsites. The Igeo values except for Ni, Cu and Mn at Eneka dumpsite, Cr and As in all the studied dumpsites revealed moderate to heavy contamination. Pollution load index (˃ 1) was  in the studied dumpsites which implies that there is heavy metal pollution across the studied dumpsites. Anthropogenicity indicates that human activity is mostly responsible for the increase in metals in the studied area. Low ecological risk indices for the heavy metals (Ni, Cu, Cr, Mn, As) were found in all the sampling locations except for copper in Oyibo dumpsite. According to the findings, there is a low to moderate level of heavy metal pollution in the soils from the dumpsite, which can deteriorate the food ecosystem if adequate measures are not put in place.

The geochemical forms of some heavy metals in refuse dump soils at Agu-Awka, Awka metropolis was studied in order to assess the mobility and bioavailability of the metals and hence their potential environmental risk. Exchangeable fraction (F1) contained the % fraction of 13.23% for Cd, 17.43% for Cr, 14.63% for Pb, 12.40% for Ni, 25.34% for Zn and 15.92% for Mn and these are in the order of Zn ˃ Cr ˃ Mn ˃ Pb ˃ Cd ˃ Ni. The carbonate fraction (F2) contained the % fraction of 17.08% for Cd, 17.84% for Cr, 9.20% for Pb, 28.32% for Ni, 13.76% for Zn and 8.49% for Mn and these are in the order of Ni ˃ Cr ˃ Cd ˃ Zn ˃ Pb ˃ Mn. Lead was predominantly associated with organic fraction with a result of 42.64% followed by chromium and manganese with the values of 22.48% and 20.00% respectively. The organic bound metals were in the abundance trend of Pb ˃ Cr ˃ Mn ˃ Cd ˃ Ni ˃ Zn. The highest values of metal in Fe-Mn oxide phase was manganese with a value of 32.18%, followed by cadmium with the value of 21.76%. The values of the other metals bound to this phase were 17.52%, 16.64%, 13.99% and 12.90% for Zn, Ni, Cr, and Pb respectively. Zinc with the value of 32.20% was predominantly associated with the residual fraction. The other metals bound to this phase had their values to be 30.13% for cadmium, 28.24% for chromium, 20.61% for lead, 29.41% for nickel and 23.37% for manganese. The mobility factor values of the metals were relatively low and they followed the order of Ni > Zn > Cr > Cd > Mn > Pb. That notwithstanding, soils from studied area should be carefully monitored to prevent the release of these metals due to redox reactions which may make them available to plants through absorption.