CO2, Environmental Emergencies, and Industrial Pollution Assessment in China from the Perspective of the Circular Economy

The rise of energy consumption has also increased emissions of the “three wastes” (wastewater, waste gas, and industrial solid waste), and environmental emergencies caused by pollutants, natural disasters, and production safety accidents have aroused social concerns. As few scholars have combined treatment efficiency of the three wastes with environmental emergencies to explore their relationships, this research thus uses a two-stage undesirable Data Envelopment Analysis (DEA) method to explore the situations of 4 regions and 30 provinces in China from 2013 to 2017 based on such interactive perspectives. The study finds that the overall regional environmental efficiency in China is generally low, and in terms of regional differences, the eastern and northeastern regions are better than the central and western regions. The efficiency values of the three wastes in China have also fluctuated greatly from 0.7 down to 0.2 in recent years. The efficiency of environmental emergencies in China is greatly impacted by the efficiency of environmental governance inputs. Based on the results, the study proposes that the eastern provinces can be an example for promoting balanced regional development and offers policy recommendations such as taking precautions against environmental emergencies.

Study of Semi-Dry High Target Solidification/Stabilization of Harmful Impurities in Phosphogypsum by Modification

Phosphogypsum (PG) treatment is one of the research hotspots in the field of environmental protection. Many researchers both at home and abroad have devoted themselves to studies on harmless resource treatment of PG, but the treatment technology is unable to meet the demand of PG consumption due to the huge production and storage demands. In order to solve the problem of PG pollution, this study explored the different solidified effects of various modification formulations on the hazardous components in PG, using industrial solid waste calcium carbide slag (CCS) as an alkaline regulator; Portland cement (PC), polyaluminum chloride (PAC) and CaCl2 as the main raw materials of the solidification and stabilization formula and the water content in PG as the reaction medium. The results showed that CCS (0.5%), PC (0.4%) and PAC (0.3%) had a more significant solidified effect on phosphorus (P) and fluoride (F). PAC was added in two steps and reacted under normal temperature and pressure, and its leaching toxicity meets the requirements of relevant standards, which laid an excellent foundation for PG-based ecological restoration materials and filling materials, with low economic cost, simple process and strong feasibility. This will provide great convenience for the later mining and metallurgy.

Non-Fired Building Blocks Using Industrial Wastes

Bricks produced from traditional techniques and agricultural clay contribute considerably to the air pollutions in the world. Therefore, an urgent need to start using an environment-friendly alternative material/approach to save the fertile topsoil and conserve a clean environment. This research is aimed to produce non-fired bricks incorporating industrial solid waste from steel and power plants, including Fly ash and Ladle Furnace Slag (LFS), as a partial replacement of CEM I and lime. Induction Furnace Slag (IFS) is used as a partial/full replacement of natural fine aggregate (local sand) in the laboratory scale manufacturing process. The prepared building blocks conform to the minimum compressive strength requirement of 10.3 MPa per ASTM C62 and BDS 208 while the maximum compressive strength was 40.6 MPa. This highly promising performance pronounced the use of industrial waste materials in non-fired brick production to achieve a cleaner environment for a sustainable society. ournal of Engineering Science 12(3), 2021, 1-10

The study on the effect of flotation purification on the performance of α-hemihydrate gypsum prepared from phosphogypsum

Phosphogypsum (PG) is a massive industrial solid waste. In this paper, PG was purified by flotation method, and α-hemihydrate gypsum (α-HH) was prepared by the autoclaving method. The morphology of α-HH was adjusted by adding different doses of Maleic acid and Aluminium sulfate. The results showed that after flotation purification, the impurity content in PG was significantly reduced, the soluble phosphorus content decreased from 0.48 to 0.07%, the PG purity increased from 73.12 to 94.37%, and the PG whiteness risen from 19.4 to 40.5. Then the performance of α-HH prepared from PG before and after purification was compared. Fixing the amount of aluminium sulfate at 0.2 wt%, the reaction temperature at 140 °C, and the reaction time at 120 min, the average length/diameter ratio of α-HH crystals decreased from 7.2 to 0.6 as the amount of Maleic acid increased from 0 to 0.17 wt%. When the amount of Maleic acid was 0.13 wt%, the α-hemihydrate gypsum reached the best mechanical properties. The mechanical strength of high strength gypsum prepared from PG concentrate was significantly better than that of raw PG, indicating that flotation purification can effectively improve the performance of PG. In this study, a new method of PG purification and resource utilization was proposed.

Assessment of groundwater quality of two selected villages of Nawada district of Bihar using water quality index

Unplanned discarding of industrial effluent, sewage, domestic and industrial solid waste, unwise use of insecticides, herbicides, pesticides, and fertilizer in agriculture are the major causes of groundwater quality reduction. In the present paper groundwater quality of the two selected village of Rajauli subdivision of Nawada district of Bihar was assessed using water quality index (WQI). The samples were figured out for the parameters such as temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), alkalinity, dissolved oxygen (DO), total hardness (TH), chloride, calcium (Ca), magnesium (Mg), biochemical oxygen demand (BOD), and fluoride. All the parameters were found below the standard limits of Bureau of Indian Standard (BIS, 2012) except total hardness (328.1mg/l to 346.6mg/l), calcium (105.3mg/l to 122.6mg/l), magnesium (46.1mg/l to 55.7mg/l) and fluoride (4.8 to 4.9mg/l). Fluoride was observed more than 3 times than the standard permissible limit (1.5mg/l). Water quality index (WQI) was also applied on the obtained data to make it easy to understand. Based on WQI (including the fluoride), all the four sites fall in unfit for drinking category (250.79, 258.78, 281.78, 247.30) and in poor to very poor category (80.23, 88.19, 88.59, 64.60) excluding the fluoride from WQI calculation. Both the values of WQI shows that fluoride alone is not responsible for the degraded quality of water but other high concentration of salts is also responsible.

Correspondence Between Technology Options Available for Chemical Industries and the Levels of the Waste Management Hierarchy: A Case Study Approach

The Waste Management Hierarchy is used as a guiding principle for waste management of industrial solid waste. Further, it is extended for the management of industrial liquid effluents as well. The Waste Management Hierarchy consists of the five levels namely; waste prevention, reuse, recycling, recovery, and disposal. This five-tiered Waste Management Hierarchy has been adopted by the European Union under the Waste Framework Directive as a decision-making tool. This paper explores some of the technology options known and available and categorizes them according to the five levels of the Waste Management Hierarchy. This paper presents brief case studies that highlight some benefits to those who embrace this decision-making tool.

Preparation and Properties of a Sulphoaluminate Magnesium-Potassium Phosphate Green Cementitious Composite Material from Industrial Solid Wastes

The preparation of high-performance green cementitious material from industrial solid waste is a feasible large-scale utilization approach for industrial solid waste. This work investigates the feasibility of using industrial solid wastes in a sulphoaluminate–magnesium–potassium–phosphate cementitious composite material (SAC-MKPC) clinker preparation and the influence of the calcination temperature and clinker ingredients on the hydration behavior and mechanisms of the SAC-MKPC with a Mg/P ratio of 5. The results show that the novel SAC-MKPC that was prepared from aluminum slag, carbide slag, coal gangue, and magnesium desulfurization slag was composed mainly of mineral MgO, C4A3S¯, and C2S and the calcination temperature of the main mineral phases was 1250–1350 °C. The solid-waste-based SAC-MKPC had better mechanical properties and excellent water resistance compared with the MKPC. The optimal compressive strength reached 35.2, 70.9, 84.1, 87.7, and 101.6 MPa at 2 h, 1 d, 3 d, 7 d, and 28 d of hydration, respectively. The X-ray diffraction spectra and scanning electron micrographs of the hydration products of the SAC-MKPC clinker showed that AFt and K-struvite crystals coexisted and adhered to form a dense structure. This work provides an innovative idea to produce green cementitious material using industrial solid wastes and may promote the sustainable development of the power and mining industries.