Catalytic recovery of metals from end-of-life polycrystalline silicon photovoltaic cells: Experimental insights into silver recovery.

A steady increase in end-of-life (EoL) polycrystalline silicon photovoltaic (c-Si PV) panels is necessitating the development of recycling technologies to guarantee sustainable environmental management and a circular economy. Herein, we propose a comprehensive EoL c-Si PV recycling strategy with an emphasis on selective silver (Ag) recovery. Primarily, a combination of physical and thermal treatment led to the isolation of PV cell fraction from the EoL PV module. Thereafter, a less-toxic, sulphuric acid-hydrogen peroxide (1 M H2SO4- H2O2 1% (v/v %)) lixiviant was used for Ag leaching at 70 °C. A novel catalytic process using platinum-embedded activated carbon (Pt/AC) was used with only hydrogen gas and air to recover selectively and concentrate the Ag+ from the synthetic PV cells leachate. Finally, pure metallic silver (Ag > 99.0 %) was obtained by the conventional electrowinning process. This study also proposes an explicit recovery process for Al, Cu, and Si. In addition, the Pt/AC catalytic process could efficiently recover Cu from the PV cells, similar to Ag. Following the complete recovery of Ag and Cu through Pt/AC, there is sufficient scope to isolate other metals like Al and Pb leaving behind crude Si wafers. Hence, the as-proposed recycling and metal recovery process is a newer approach benefiting industrial implementation.

Comparison of models to identify lame cows based on gait and lesion scores, and limb movement variables.

Bovine lameness results in pain and suffering in cattle and economic loss for producers. A system for automatically detecting lame cows was developed recently that measures vertical force components attributable to individual limbs. These measurements can be used to calculate a number of limb movement variables. The objective of this investigation was to explore whether gait scores, lesion scores, or combined gait and lesion scores were more effectively captured by a set of 5 limb movement variables. A set of 700 hind limb examinations was used to create gait-based, lesion-based, and combined (gait- and lesion-based) models. Logistic regression models were constructed using 1, 2, or 3 d of measurements. Resulting models were tested on cows not used in modeling. The accuracy of lesion-score models was superior to that of gait-score models; lesion-based models generated greater values of areas under the receiving operating characteristic curves (range 0.75 to 0.84) and lower mean-squared errors (0.13 to 0.16) compared with corresponding values for the gait-based models (0.63 to 0.73 and 0.26 to 0.31 for receiving operating characteristic and mean-squared errors, respectively). These results indicate that further model development and investigation could generate automated and objective methods of lameness detection in dairy cattle.

A noninvasive radiotelemetry system to monitor heart rate for assessing stress responses of bovines.

A noninvasive radiotelemetry system was developed to monitor heart rates of cows and to view and analyze data. The system was validated by comparing heart rate data of two restrained heifers collected simultaneously using telemetric and direct electrocardiogram measurements and by acquiring data over 72 h from two dry cows housed in an experimental handling facility consisting of a free-stall pen, a holding pen, a pass-through stall, and a second holding pen. Telemetric and direct measurements in response to pharmacological elevation of heart rates were essentially identical. For cows in the experimental facility, peristimulus-time histograms indexed to standing or lying showed that average heart rates for cows increased 4.0 +/- 1.4 beats/min after cows stood and decreased 4.8 +/- 1.0 beats/min after cows lay. Similarly, the average heart rate for the cow naive to the facility increased from 60 to 86 beats/min and remained elevated for 6.3 min when heart rate was indexed to maximal heart rate within +/- 3 min of entry into the pass-through stall. Heart rate for the naive cow increased consistently from around 60 to over 160 beats/min during repeated agonistic encounters between animals. Heart rate for the other cow was not affected by the encounters. These results show clearly that heart rate can be used to monitor animal anxiety.

Variation in distances among teats of Holstein cows: implications for automated milking.

Distances among teats were measured immediately prior to and immediately following milking in 912 lactations of 506 Holstein cows to assess variation due to age (parity), stage of lactation, year, and observer. Data were used to simulate success or failure to attach by the Gascoigne Melotte robotic milker. Distance between front teats premilking was nearly twice that for rear teats. When attachment of the cluster to an udder with a particular set of teat distances was simulated, excessive distance between front teats was the most frequent cause of attachment failure for third and later parities. For first parity, extremely narrow distance between rear teats was the most frequent cause of predicted attachment failure. Reduction in teat distances because of milking was proportionately much greater for distance between rear teats (45 to 50%) than for other teat distances (25 to 29%). In a study of 10 Holstein cows measured at milking and at 0, 6, 8, and 12 h after milking, distances among teats increased linearly with time elapsed postmilking. Electronic storage of a profile of a cow for teat distance and adjustments for milking interval and stage of lactation can increase chances for successful cluster attachment.

Effect of dietary calcium concentrations during gestation and lactation in the sow on milk composition and litter growth.

This study evaluated the effects of diets containing varying amounts of Ca on milk composition and litter characteristics of sows. Yorkshire sows were fed one of the following diets: low Ca (.38%; n = 5), standard Ca (.75%; n = 5), or high Ca (1.12%; n = 4). Diets were fed from d 42 of gestation to d 42 of lactation. Milk was collected on d 7 +/- 1, 21 +/- 1, and 42 +/- 1 of lactation. Lactose was greater (6.4%, P < .05) in milk from sows fed low Ca than in those fed standard (5.5%) or high (5.8%) Ca, but only on d 7 of lactation. No treatment effect or time x treatment interaction was detected for total protein or casein concentrations. Calcium increased (P < .05) over time irrespective of treatment. There was an increase (P < .05) in ADG on d 7 in pigs from high-fed (.28 kg) and low-fed sows (.20 kg) compared with those from standard-fed sows (.13 kg). In conclusion, body Ca is so physiologically regulated that minor dietary alterations have little overall effect on milk composition. Alterations in ADG for pigs, especially from sows fed high Ca, warrant further investigation.

A microcomputer-photocell system to monitor periparturient activity of sows and transfer data to remote location.

A microcomputer-photocell system to record, summarize and transfer data on the postural changes of crate-confined sows was developed. The system uses an infrared photocell system mounted on farrowing crates to detect changes in sow body postures prior to parturition. When a sow breaks the infrared beam by standing or sitting, the lack of reflection back to the photocell activates a relay. The relays are connected to an input/output card inside the primary ("host") microcomputer. A second microcomputer, at a location remote to the animal facility, and the host computer both are equipped with multi-tasking operating systems. The host computer uses a data acquisition program written in BASIC to record posture changes, the sow's identifying number, date and time. Both computers are equipped with communications software so that the host computer can transfer data to the remove location while continuing to collect data. Either computer can be used to summarize, graph and examine the accumulated data. Knowledge of periparturient activity patterns allows the observer to predict farrowing time and to determine whether farrowing has begun without being present in the farrowing facility.