Cleaning Using CO2‐Based Solvents

Cleaning with hierarchy of CO₂‐based solvents is advantageous from an environmental point of view because CO₂ is non‐flammable, virtually inert, and abundant. After cleaning, the only waste stuffs generated are the contaminants that are removed from the cleaned parts. The technology is especially well suited for precision cleaning applications in which parts have intricate geometries or for applications in which parts are sensitive to water or high temperature. This review will first introduce aqueous cleaning concepts and mechanism, which is helpful to understand how to design cleaning systems using high pressure CO₂. Recent microelectronic processes for cleaning and rising of circuit wafers using CO₂‐based solvents are the main focus of the review. Additional cleaning topics include dry cleaning, separation of dyestuffs, and extraction of contaminations from soils and regeneration of catalysts.     

Use of Magnet Technology for Phosphate Elimination from Municipal Sewage

The present report describes the set-up and first operation results of a novel carousel magnetic separator. This carousel magnetic separator is suitable for continuous separation of magnetized particles from water. Continuous operation is achieved by a segmented rotating separation matrix. This matrix also allows the use of low-cost permanent magnets, by means of which magnetic fields of up to 0.5 T can be generated without energy consumption. The suitability of a first prototype of this carousel magnetic separator was tested for elimination of magnetite-containing iron phosphate and iron hydroxide flocs. These flocs result from conventional precipitation/flocculation of municipal sewage with FeCl₃ and the addition of magnetite particles generated by wet-chemical processes. First results demonstrate that the carousel magnetic separator can reduce phosphate concentrations of up to 14 mg/L PO₄^3–-P in the inlet to below 1 mg/L PO₄^3–-P in the outlet at filtration rates of about 40 m/h. Magnetite dosage in the range of 50 mg/L affects phosphate precipitation positively via a slight reduction of the precipitant volume. However, the total amount of chemicals required for phosphate elimination is increased by the substances needed for magnetite production. Therefore, a further reduction of magnetite dosage must be achieved.     

Bias of ostracod stable isotope data caused by drying of sieve residues from water

Stable isotope analysis of ostracod shells is used routinely for palaeoenvironmental studies of ostracod-bearing records. Sample treatment usually involves the disaggregation of sediments and sieving; before the sieving residues were washed with water onto petri dishes and oven-dried. In our study, we compared δ¹⁸O and δ¹³C values of shells that were oven-dried from water and from ethanol alternatively. Large isotopic differences of up to 3‰ were determined for δ¹⁸O values, whereas differences in δ¹³C values were less pronounced with differences of up to 1.6‰. Stable isotope values of shells dried from water were lower for both oxygen and carbon as a result of calcite crystals precipitated on the shell surfaces during the drying process. Therefore, ostracod shells for stable isotope analysis should not be prepared by drying from water. Instead, shells should be dried from ethanol to obtain reliable stable isotope data; likewise freeze-drying is expected to provide trustworthy results.     

电炉炼钢烟气特点及捕集净化措施

通过介绍电炉烟气的特点并对目前国内外所采取的各种电炉烟气捕集净化措施进行描述和分析,提出了适合我国国情的电炉烟气捕集形式,并就电炉烟气的净化提出了解决二英等污染物的治理对策。     

Packed‐Column of Granular Activated Carbons for Removal of Chemical Oxygen Demand from Industrial Wastewater

In the present study, chemical oxygen demand (COD) removal by packed‐columns of activated carbon (AC) derived from two different materials (coal activated carbon, CAC and wood activated carbon, WAC) is reported as part of an on‐site wastewater treatment system for handling small volumes of wastewater generated at wood‐floor industries for which there are no proper on‐site treatment options available in the market. The performance of the sorbents, the effect of bed depth (0.19 and 0.57 m) and volumetric load (0.10 and 0.24 m h^?1) on the breakthrough curve of sorption systems were studied. The results indicated the feasibility of using both ACs to treat these wastewaters. At the bed depth (0.57 m), volumetric load (0.24 m h^?1), and 30% breakthrough, CAC and WAC showed treatment capacity of 40.5 L kg^?1 in 250 h and 23.8 L kg^?1 in 63 h, respectively. This indicated that CAC requires longer retention times to reach a performance similar to WAC. The experimental data was fit into the bed depth‐service time model showing that under the same conditions, CAC had higher maximum sorption capacity (N₀) than WAC. Moreover, thermal regeneration at 500°C temperature could be a cost‐effective procedure since the reuse of spent AC through such regeneration process for further treatment could still achieve 90% of the initial sorption capacity, reducing then costs for the use of new sorbents and also the need for waste disposal.     

Recovery of Polyvinyl Alcohol from Desizing Wastewater Using a Novel High‐Shear Ultrafiltration Module

Polyvinyl alcohol (PVA), the major constituent of desizing water constituting 45% of the total BOD load has a significant environmental impact owing to its poor biodegradability. In order to prevent PVA from being discharged by the effluent stream, modern textile industries opt for membrane based separation techniques using ultrafiltration so that the recovery and recycle of PVA in tandem could be achieved. However, the process of ultrafiltration is still not widely accepted as expected due to the well‐known non‐idealities of concentration polarization and pore blockage. In this article, design and performance characterization of a lab‐scale novel shear enhanced ultrafiltration unit, named as spinning basket membrane (SBM) module are discussed. The proposed module is unique in terms of its inbuilt cleaning facility eliminating the effects of polarization and subsequent periodic fouling leading to its uninterrupted production operation. The test fluid, necessarily a solution of PVA was treated in the proposed module under different parametric conditions with polyvinylidene fluoride (PVDF) membranes of two different molecular weight cut‐off (50 and 100 kDa). After 2 h of continuous operation the permeate flux was observed to be within 95–97% of the respective initial fluxes. Such performance is rarely been attained in practice. Hence, the novelty of the present research is achieved. Considering the performance of the present module in terms of flux regeneration and product recovery, it may be regarded as an efficient device and can be potentially deployed for cleaning of other industrial wastewater.     

An experimental evaluation of cleaning methods for fossil ostracod Mg/Ca and Sr/Ca determination

To evaluate the effect of sample preparation on the trace element composition of ostracod shells, fossil shells subjected to various cleaning steps were analyzed by ICP-AES. The variations in ostracod Mg/Ca ratios reveal that fossil ostracod samples cleaned by ultrasonic methanol yield lower values than those by other methods, including increasingly rigorous reductive cleaning. In our sample sets, shell Mg/Ca decreases ∼ ∼1.5 mmol/mol during clay removal. Sample Sr/Ca results do not seem to vary significantly under the equivalent cleaning steps. For ostracod analysis, pre-treatment using multiple methanol ultrasonic cleaning is suggested to be used for gaining an appropriate result.     

Size affects digestive responses to increasing temperature in fishes: physiological implications of being small under climate change

Digestive metabolism is considered key to resilience of fish populations as it determines energy and nutrient availability for growth and survival. In cleaner fishes, digestion performance also influences the amount and the rate at which parasites can be removed from co‐operating fishes, called hosts. Therefore, understanding the effect of temperature on digestive metabolic scope (i.e. the energy allocated to digestive processes) is crucial to predicting responses of fish communities to ocean warming. Body size can affect many physiologic processes and is thought to decrease with increasing temperature; therefore, we examined the effect of body mass and warming on digestive metabolic scopes in two sister species of cleaner gobies of the genus Elacatinus that reach different adult sizes. The dwarf‐size Elacatinus lobeli increased digestive metabolic rates and scope while the larger Elacatinus oceanops decreased digestive metabolic scope with warming. Intra‐specifically, larger E. lobeli also showed a decreased scope when compared to smaller individuals. Results from this study suggest that perhaps smaller fishes may have a digestive and metabolic advantage at higher temperatures and may be more resilient under warming temperatures.