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Construction is among the leading industries/activities contributing the largest carbon footprint. This review paper aims to promote awareness of the sources of carbon footprint in the construction industry, from design to operation and management during manufacturing, transportation, construction, operations, maintenance and management, and end-of-life deconstruction phases. In addition, it summarizes the latest studies on carbon footprint reduction strategies in different phases of construction by the use of alternative additives in building materials, improvements in design, recycling construction waste, promoting the utility of alternative water resources, and increasing efficiencies of water technologies and other building systems. It was reported that the application of alternative additives/materials or techniques/systems can reduce up to 90% of CO2 emissions at different stages in the construction and building operations. Therefore, this review can be beneficial at the stage of conceptualization, design, and construction to assist clients and stakeholders in selecting materials and systems; consequently, it promotes consciousness of the environmental impacts of fabrication, transportation, and operation.

In this study, pristine biochar derived from date palm at 500°C was used in batch reactors (simulating blending adsorbent in aeration tank) and fixed-bed columns (simulating holding adsorbent in fixed-bed reactors). The removal performance of the biochar was assessed toward single and mixed-metal solutions as well as synthetic primary and secondary treated wastewater for copper (Cu 2+ ), iron (Fe 2+ ), nickel (Ni 2+ ) and zinc (Zn 2+ ). The order of maximum adsorption capacities of the metal ions at pH 7 followed: Fe 2+ (2.92/2.94 mg/g)>Cu 2+ (2.69/2.78 mg/g) >Zn 2+ (2.03/2.19 mg/g)>Ni 2+ (1.69/1.02 mg/g) in single/mixed-metal solutions and Zn 2+ (2.91/11.26 mg/g)>Fe 2+ (0.60/5.29 mg/g)>Cu 2+ (0.56/5.05 mg/g)>Ni 2+ (0.13/2.02 mg/g) in synthetic primary/secondary treated wastewater. Blending biochar in aeration tank reduced metal concentrations. The metal ion concentrations in the final effluent were below the World Health Organization drinking water limits (2, 0.3, 0.1 and 3 mg/L for Cu 2+ , Fe 2+ , Ni 2+ and Zn 2+ , respectively) suggesting that treated secondary wastewater can be spread into potable aquifers following disinfection. The Freundlich and the Pseudo-second order models fit best the batch experimental data. Experimental data from column analysis fit well to the Thomas model. The adsorption of metal ions on the surface of biochar was confirmed by Scanning electron microscopy, Energy dispersive X-ray studies, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Desorption studies using different eluents demonstrated the reusability potential of the studied biochar.

In this study, leaf and frond date palm waste as feedstock was used to derive biochars. The effects of pyrolysis temperatures on their physical and chemical properties, and their capacity to remove copper, iron, nickel and zinc from single and multi-metal solutions at various pH values were investigated. Analytical and spectroscopic techniques such as scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy, X-ray diffraction, carbon, hydrogen, nitrogen, sulfur elemental analysis, Brunauer Emmett Teller analysis were conducted for characterization. The pore volume, surface area, pH, and total carbon content of date palm leaf and frond biochar increased while functional groups and hydrogen, nitrogen and oxygen content of biochar decreased with increasing pyrolysis temperature compared to feedstock. The removal efficiencies and sorption capacity for single and mixed metal ions were found between 98 and close to 100% and 2.4 and 3.0 mg g − 1 by leaf and frond biochar samples at pH > 6, respectively. Biochar obtained from different feedstock at different pyrolysis temperature did not show any statistically significant improvements on the removal of single or mixed metals from aqueous solutions. The date palm leaf or frond biochar obtained at low pyrolysis temperature is as effective to remove metals as the ones obtained at high pyrolysis temperatures. Therefore, to consume less energy to produce biochar at lower temperature which exhibits same effective removal efficiency will be a win-win solution in terms of sustainability and economy. As a result, date palm waste biochar can be effectively used to remove metals in water and wastewater.

In this study, pristine biochar derived from date palm at 500°C was used in batch reactors (simulating blending adsorbent in aeration tank) and fixed-bed columns (simulating holding adsorbent in fixed-bed reactors). The removal performance of the biochar was assessed toward single and mixed-metal solutions as well as synthetic primary and secondary treated wastewater for copper (Cu2+), iron (Fe2+), nickel (Ni2+) and zinc (Zn2+). The order of maximum adsorption capacities of the metal ions at pH 7 followed: Fe2+ (2.92/2.94 mg/g)>Cu2+(2.69/2.78 mg/g) >Zn2+(2.03/2.19 mg/g)>Ni2+(1.69/1.02 mg/g) in single/mixed-metal solutions and Zn2+(2.91/11.26 mg/g)>Fe2+(0.60/5.29 mg/g)>Cu2+(0.56/5.05 mg/g)>Ni2+(0.13/2.02 mg/g) in synthetic primary/secondary treated wastewater. Blending biochar in aeration tank reduced metal concentrations. The metal ion concentrations in the final effluent were below the World Health Organization drinking water limits (2, 0.3, 0.1 and 3 mg/L for Cu2+, Fe2+, Ni2+ and Zn2+, respectively) suggesting that treated secondary wastewater can be spread into potable aquifers following disinfection. The Freundlich and the Pseudo-second order models fit best the batch experimental data. Experimental data from column analysis fit well to the Thomas model. The adsorption of metal ions on the surface of biochar was confirmed by Scanning electron microscopy, Energy dispersive X-ray studies, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Desorption studies using different eluents demonstrated the reusability potential of the studied biochar.

The impact of water pollution has led to the search for cost-effective and environmentally friendly treatment processes to alleviate the associated environmental hazards. Adsorption is identified as an advanced treatment technology that offers simplicity and cheap alternatives to water treatment technologies when low-cost adsorbents such as industrial by-products, waste, and agricultural waste are utilized. The utilization of these materials as low-cost adsorbents for the treatment of drinking water will bring them some value. Several practices have been done to improve the removal efficiencies of the low-cost adsorbents in order to achieve WHO standards of drinking water quality. The paper highlights some of the synthesis routes employed for the modification of low-cost adsorbents. This updated review provides information on the different applications of low-cost adsorbents in removing pollutants and their adsorption capacities in an attempt to deploy the recent sustainable low-cost adsorbents with high removal efficiencies for water treatment. Future research should focus on the fabrication of hybrid low-cost adsorbents with multifunctional and antimicrobial properties. In addition, life cycle assessment (LCA) should be conducted to reveal the environmental burdens associated with the modification of the low-cost adsorbent to improve their removal efficiencies.