No abstract

A method to recover hardwood kraft lignin by acidification of black liquor using waste acid from a Mathieson chlorine dioxide generator is proposed. Optimum reaction conditions to maximize the lignin yield and minimize acidification costs were determined. To analyze the effects of the major variables, a 23 factorial model describing the effects of acidification temperature, degree of agitation, and rate of waste acid addition was developed. Increasing the acidification temperature improved the lignin precipitation and filterability. However, the maximum practical temperature was 70 °C because the lignin precipitate starts to form a tarlike substance at approximately 80 °C. Also, the rate of acid addition should be minimized. In practice, this will be determined by the mill reaction vessel size, which depends on the black liquor flow rate to be acidified. Last, the stirring rate should be kept as low as possible, although some agitation is still required to uniformly mix the acid and black liquor. A steady-state computer simulation of incorporating a proposed 21 ton/day hardwood lignin recovery plant to the kraft liquor cycle showed no adverse effects in the chemical balance of the mill.

Abstract. In Nepal and many developing countries around the world, roads are vehicles for development for communities in rural areas. By reducing travel time on foot, opportunities are opened for quicker transportation of goods and better access to employment, education, health care and markets. Roads also fuel migration and numerous social changes, both positive and negative. Poorly constructed roads in mountainous areas of Nepal have increased erosion and landslide risk as they often cut through fragile geology, destabilizing slopes and altering local hydrological conditions, with costs to lives and livelihoods. The convergence of the newly constituted decentralized Nepali government with China's Belt and Road Initiative is likely to bring more roads to rural communities. The new provincial government administrations now have the opportunity to develop policies and practices, which can realign the current trend of poorly engineered, inefficient and hazardous road construction toward a more sustainable trajectory. This commentary provides an overview of some of the obstacles along the way for a more sustainable road network in Nepal and illustrates how good governance, development and landslide risk are intertwined. The opinion presented in this brief commentary lends little hope that Nepal's current pathway of unsustainable road construction will provide the country with the much-needed sustainable road network, unless checks and balances are put in place to curb noncompliance with existing laws and policies.

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Landslides pose significant hazards on the road network of Laos. These landslides frequently block access and occasionally result in the subsidence or loss of the carriageway. Several slope stabilization trials focusing on the use of bioengineering techniques and low-cost engineering measures were implemented in 2007 and 2008. Heavy rains in 2018 caused numerous landslides on the road network and a review was undertaken of the performance of the slope stabilization trial sites implemented ten years earlier. The outcome has proved very positive overall and vindicates the efforts made to understand the causes and mechanisms of the observed slope failures and the ground conditions that pertained. The outcomes of this research have been used to strengthen practice in Laos, and further afield, and to provide a valuable basis for future practice.