Neeraj Jain

Biosorption of Chromium(VI) From Aqueous solutions by green algae spirogyra species

Biosorption of heavy metals is an effective technology for the treatment of industrial wastewaters. Results are presented showing the sorption of Cr(VI) from solutions by biomass of filamentous algae Spirogyra species. Batch experiments were conducted to determine the adsorption properties of the biomass and it was observed that the adsorption capacity of the biomass strongly depends on equilibrium pH. Equilibrium isotherms were also obtained and maximum removal of Cr(VI) was around 14.7 x 10(3) mg metal, kg of dry weight biomass at a pH of 2.0 in 120 min with 5 mg/l of initial concentration. The results indicated that the biomass of Spirogyra species is suitable for the development of efficient biosorbent for the removal and recovery of Cr(VI) from wastewater.

EFFECT OF INORGANIC MATERIALS ON THE SOLIDIFICATION OF HEAVY METAL SLUDGE

Abstract Portland cement, cement–fly ash and lime–fly ash binders were used to solidify a synthetic heavy metal sludge containing nitrates of Cr, Ni, Cd and Hg. The sludge to binder (cement, cement–fly ash and lime–fly ash) ratio was kept at 3.33, 1.43 and 1.25, respectively. In addition inorganic substances like Cu, Zn, Pb, Sodium hydroxide and sodium sulfate were added. The molded samples were cured at room temperature for 28 days. The solidified samples with and without interference were examined for the change in their bulk density and compressive strength at definite time intervals during curing. All the metals and sodium salts added increased the average bulk density of the final product with increase in concentration (2% to 8%) with all the binder systems. The samples containing copper and lead decreased the compressive strength at all the concentrations added with CFA and LFA binders. Zn had the largest effect on all the three binder systems, lowering the strength of all samples at all the days and concentrations except the 2% Zn with CEM binder. However, Pb had only minor effect on the compressive strength with CEM binder and values remained almost constant at all the times and concentrations studied. In contrast, the effect of sodium sulfate was less marked while sodium hydroxide increased the rate of set and 28-day compressive strength of samples containing cement as binder. These observations confirm the need for specific studies of the waste and binder prior to the selection of a solidification process for the treatment of hazardous wastes. The results provide a better understanding of materials that may interfere with the immobilization of waste constituents and provide information on the possible mechanism of the interfering effects.

Effect of organic materials on the solidification of heavy metal sludge

Abstract Solidification studies were conducted using three binders, viz., Portland cement (CEM), cement-fly ash (CFA) and lime-fly ash (LFA) to solidify a synthetic heavy metal sludge containing nitrates of Cr, Ni, Cd and Hg. The sludge to binder (CEM, CFA, LFA) ratio was kept at 3.33, 1.43 and 1.25, respectively; and the effect of additive interfering organic substances like grease, oil, hexachlorobenzene (HCB), trichloroehtylene (TCE) and phenol was observed. The molded samples were cured at room temperature for 28 days and the solidified samples with and without interference were examined for the change in their physical and containment properties like bulk density and compressive strength at definite time intervals during the process of curing. The results of the analysis indicated that phenol, grease and oil had a significant detrimental effect on the compressive strength of the solidified samples during the process of curing. In contrast, the effect of HCB and TCE was less marked on the compressive strength of the sample. The observations confirm the need for the waste to binder specific studies prior to the selection of a solidification process for the treatment of hazardous waste. The results also revealed a better understanding of materials that may interfere with the immobilization of the waste constituents.

Green Concrete from Sustainable Recycled Coarse Aggregates: Mechanical and Durability Properties

Present investigations deal with the development of green concrete (M 30 grade) using recycled coarse aggregates for sustainable development. Characterization of recycled coarse aggregates showed that physical and mechanical properties are of inferior quality and improvement in properties was observed after washing due to removal of old weak mortar adhered on its surface. The influence of natural coarse aggregates replacement (50 and 100%) with recycled coarse aggregate on various mechanical and durability properties of hardened concrete were discussed and compared with controls at different w/c ratio. Improvements in all the engineering properties of hardened concrete were observed using washed recycled coarse aggregates. The compressive strength of 28-day hardened concrete containing 100% washed recycled aggregate was slightly lower (7%) than concrete prepared with natural aggregates. Water absorption, carbonation, and rapid chloride penetration test were conducted to assess the durability of the concrete. Concrete was found moderately permeable for chloride ions penetration and no carbonation was observed in all the concrete mixes studied.

Fabrication of Green Bricks Utilizing Sustainable Recycled Fine Aggregates

The objective of the present research is fabrication of bricks by the incorporation of recycled fine aggregate obtained from crushing of waste concrete and evaluation of the physical and mechanical properties of bricks. The natural fine aggregate and stone dust were replaced by recycled fine aggregate at a level of 50, 75 and 100 % for fabrication of bricks. Properties like Bulk density, water absorption and compressive strength were evaluated after a period of 28 days of curing and discussed. At 50 % replacement, maximum compressive strength of 6.37 and 7.68 MPa has been observed for natural fine aggregate and stone dust respectively and it is 8.7 and 25.6 % higher than respective controls. The results of compressive strength are encouraging using stone dust as fine aggregate as compared to river sand. Further, it has also been observed that the compressive strength and bulk density of all the bricks fabricated using recycled fine aggregates meets the 28-day target strength as per IS: 1077 and was not less than 5.0 MPa in any case. Keywords: Recycled fine aggregates, molded bricks, compressive strength, stone dust, water absorption, bulk density