Maryam Rabiee Abyaneh; Gholamreza Nabi Bidhendi; Ali Daryabeigi Zand
Abstract
Introduction: Landfill leachate is a highly toxic and hazardous form of wastewater due to its complex composition characteristics. Effective removal of heavy metals from landfill leachate is of great concern due to the fact that toxic metals can seriously threaten the food chain, and therefore the human ...
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Introduction: Landfill leachate is a highly toxic and hazardous form of wastewater due to its complex composition characteristics. Effective removal of heavy metals from landfill leachate is of great concern due to the fact that toxic metals can seriously threaten the food chain, and therefore the human health. The main objective of this work was to study the utilizing of low-cost pruning residues in the production of biochar and its application in removal of lead (Pb) from landfill leachate.Material and methods: Leachate produced in Babol municipal solid waste landfill was used as an adsorbent solution. Pruning residues were collected and used for biochar preparation. Biochar produced under the pyrolytic temperature of 700°C with a 1-hour retention time. The adsorption mechanism of pruning waste biochar to Pb was analyzed through BET surface area and scanning electron microscope (SEM) tests. Batch experiments were performed to study the effects of adsorption parameters on Pb removal. The influence of contact time (30-300 min), adsorbent dosage (1-50 g/L), as well as particle size (1-2 mm and 63-75 µm) was investigated. Moreover, the kinetic and isotherm models were applied to the experimental data to predict the adsorption parameters.Results and discussion: The results obtained from the analysis of the untreated Babol landfill leachate was revealed that the Pb concentration was about 4.94 mg L-1. The surface area of the produced biochar was determined to be 292.44 m2 g-1. SEM microstructure of the biochar showed the developed surface area with visible pores. All of these data seem to suggest a great potential for pruning residues biochar to Pb removal. The adsorption of Pb was mainly affected by contact time, adsorbent dose, and biochar particle size. Higher contact time and adsorbent dosage showed higher uptake of Pb. Whereas, the uptake of Pb ions onto pruning residues biochar was substantially reduced with increase the biochar particle size. Maximum Pb percentage removal was observed at a contact time of 90 min and with an optimum biochar dosage of 20 g L-1 (89.06% removal) for biochar with 1-2 mm particle size. While, biochar with particle size of 64-75 µm can removed Pb to almost 100% at a contact time of 120 min and with an optimum biochar dosage of 20 g L-1. The kinetic study showed that adsorption can be well described by the pseudo-second order kinetic model. This supports the chemisorption theory behind the pseudo-second order kinetic model for the adsorption system. The results of isotherm models implied that the behaviors of the isotherms are more appropriate for the Langmuir model, showing a monolayer adsorption capacity for Pb.Conclusion: Findings of this research demonstrated the applicability of pruning residues biochar as an economic adsorbent for the removal of the Pb from landfill leachate. On the other hand, the crop residue burning poses a threat to the environment and human health due to the emission of toxic gasses and particulate matter. So, conversion of pruning residues to biochar and its application to heavy metal removal is a useful and environment-friendly alternative to crop residue and biomass burning.
Gholamreza Nabi Bidhendi; Maryam Rabiee Abyaneh; Omid Hassanzadeh Moghimi
Abstract
Introduction: Sustainable management of increasing amounts of municipal solid waste (MSW) has become a major environmental concern because improper MSW management leads to substantial negative environmental impacts and health and safety problems. The life cycle assessment (LCA) method has been recognized ...
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Introduction: Sustainable management of increasing amounts of municipal solid waste (MSW) has become a major environmental concern because improper MSW management leads to substantial negative environmental impacts and health and safety problems. The life cycle assessment (LCA) method has been recognized as an indispensable tool to support systematic and accurate decisions taken on waste management systems. LCA can make a comparison between different scenarios of waste management systems performance from top to bottom to assess the environmental impacts and consumption of resources. This paper aims to determine the environmental aspects of a less impactful MSW management scenario in Babol, Iran through LCA methodology.Material and methods: In order to achieve this goal, first, the composition study was conducted in Babol. The results were then utilized as a reliable data source to compare the environmental impacts of MSW management scenarios with a life cycle perspective. System boundaries included collection and transportation of MSW and its treatment and disposal by composting, recycling, incineration with energy recovery, and landfilling methods. Data on the process was evaluated with the IWM-2 model by the means of energy consumption and global warming.Results and discussion: Babol was estimated to generate 91000 tonnes of waste per year. On average, the generation of waste per capita in Babol was about 606 gr/person/day. After being collected throughout the city, the MSW was discharged at stations to transfer to the heavy vehicles and get transported to Anjil-Si complex waste process and disposal. The main component of the waste stream in Babol was food waste (65.3%). The comparative analysis of the six scenarios underscores the fact that the lower potential environmental loads were related to the 4th scenario in all the impact categories. In particular, the lowest energy use was obtained in scenario 4. In this scenario, composting (60%) and recycling (20%) were included in the waste management plan and resulted in a reduction in the amount of waste disposal as well as energy consumption in landfilling. As excess energy was produced in scenario 4 from the composting and recycling stages (by replacing the produced material with raw material consumed in the life cycle, and also by composting and producing other by-products), less amount of energy was consumed in this scenario. In the case of the global warming impact category, the least burden was originating from scenario 4 due to the reduction of greenhouse gas emissions by energy generation as a result of composting and recycling.Conclusion: According to the results, the 4th scenario (60% composting, 20% recycling, and 20% landfilling) was confirmed as the best waste final disposal alternative. In particular, CO2 emissions decreased by 54% and the energy consumption decreased by 19%, when the alternative scenario, including the recalled features, was compared to the base-case one. The majority of the MSW of Babol consisted of food waste. With a detailed investigation of organic waste, it is possible to benefit from the composting process as an ideal disposal method.
